Big Tyres: Pros and cons

[PAUL200]

Hi all,

I see a lot of 4WDs in Australia with large tires and lift kits etc...

Does installing big tires and lifting the suspension have much impact on the fuel economy? I know it must have some but has anyone ever measured it?

Another thing I have observed is that the military don't install all this stuff on their vehicles which makes me wonder whether it actually increases off road capability much? Are all these lifted 4WDs with big tyres just poser cars?

[Mick_Marsh]

Just fitting bigger tyres will more than likely increase fuel consumption.

When selecting a bigger tyre, think about why you are selecting it. For sand driving, a wider tyre is better, A thinner tyre is usually better for mud.
If you're after what looks good, size has no impact on the decision. It's a matter of taste.

What have you got and what are you trying to achieve?

I run 9.00 x 16 tyres on the 101. It's standard size. 7.50 x 16 on everything else, although the hybrid should probably have 205 R 16 tyres. It'd probably be a little zippier if it did.

[DiscoMick]

Yes, some people seem more interested in bling than in practicality.

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[benji]

Just look at the camel trophey. They were 205?

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[DiscoMick]

I think the various LRs in the Camel Trophy certainly ran standard size tyres for each model.
Personally, not trying to refer to anyone in particular of course, I suspect some of the big tyres I see, particularly on Toyotas and Nissans, are more about "my ego is bigger than yours" than about anything else.
The claim about increasing height for clearance is irrelevant in 99% of situations, I reckon. Wider tyres are also a handicap in mud, when you want to cut through the slush, not try to float on top of it.
So, now I suppose the big tyre fans here will be bagging me out, but honestly, I can't see many benefits in going larger than the 235/85/16s on my Defender.

[DoubleChevron]

I think the various LRs in the Camel Trophy certainly ran standard size tyres for each model.
Personally, not trying to refer to anyone in particular of course, I suspect some of the big tyres I see, particularly on Toyotas and Nissans, are more about "my ego is bigger than yours" than about anything else.
The claim about increasing height for clearance is irrelevant in 99% of situations, I reckon. Wider tyres are also a handicap in mud, when you want to cut through the slush, not try to float on top of it.
So, now I suppose the big tyre fans here will be bagging me out, but honestly, I can't see many benefits in going larger than the 235/85/16s on my Defender.

There's no doubt big mud tires will be more effective in sloppy condition.... But unless your car is a bush basher only .... 99.95% of your driving will be on a sealed road ... where mud tires suck ... Id rather it drive way, way better 99.85% of the time myself. (having said that, road tires suck big time on anything other than a sealed road). I nearly put the old rangie sideways into the trees at walking pace on road tires ..... wet clay sure is slippery. good all terrains or mud tires would have driven over it like it was a sealed road.

seeya,
Shane L.

[Mick_Marsh]

There's no doubt big mud tires will be more effective in sloppy condition.... But unless your car is a bush basher only .... 99.95% of your driving will be on a sealed road ... where mud tires suck ... Id rather it drive way, way better 99.85% of the time myself. (having said that, road tires suck big time on anything other than a sealed road). I nearly put the old rangie sideways into the trees at walking pace on road tires ..... wet clay sure is slippery. good all terrains or mud tires would have driven over it like it was a sealed road.

seeya,
Shane L.
Horses for courses, mate.
You shouldn't have muddies on the blacktop and it's not a good idea to have road tyres on the slippery stuff.
I've got Bridgestone AT on the hybrid. I swap over to Wrangler TG when the trip involves off road stuff.

[DiscoMick]

The original GG TRs on my Defender are LT, but have a mild tread which works well on road. I was surprised at how well they coped on a recent day at the Emu Creek 4WD Park near Tabulum. They were better than I had expected.
I've decided that when I replace them it will be with another LT tyre which is a mild AT.

[Slunnie]

Hi all,

I see a lot of 4WDs in Australia with large tires and lift kits etc...

Does installing big tires and lifting the suspension have much impact on the fuel economy? I know it must have some but has anyone ever measured it?

Another thing I have observed is that the military don't install all this stuff on their vehicles which makes me wonder whether it actually increases off road capability much? Are all these lifted 4WDs with big tyres just poser cars?

Military like to work with a standard - everything is the same. They will engineer for a purpose, eg the rear chassis and bodywork, but the tyres are whatever comes with it. You'll notice that every vehicle they have runs the OE tyre size. The exception is the unimog where they do have a floatation tyre for it, but they dont seem to use them these days. They did used to run open pattern tyres, but even these days they seem to have changed to a more AT type tyre, but still whatever size the factory fitted. It would be interesting to compare the Defender tyre size to the G-wagon. Are they the same, or are they the factory fitment size. I really would not use military vehicles as a benchmark on what works, what doesn't and whats a poser car - they have no interest in that type of thing, vehicles are just tools to do a job for them. If you want to know what works for bashing, look at comp cars, for touring then look at well set up touring cars, road use look at standard cars.

For economy, I changed from 29" 235/70-16 Michelin 4X4XPC to 33" 255/85-16 Cooper ST and a 4" lift, Economy was 1l/100km worse in town and 1l/100km better on the open road. When I changed to 33" 255/85-16 Cooper STT the economy was 1l/100km worse off again everywhere. I think tyre tread pattern makes the biggest difference, much more than llift or size, although I also think that if you increase tyre size it makes the consumption much less stable and predicatable.

[PAUL200]

Even with the lift kit won't the differential ground out first in most instances anyway? I think unless your rock crawling the lift thing is pointless...I saw a Patrol (with ridiculous lift kit) take a corner today and the wing mirror was nearly touching the ground!

I have the standard 235/85 16R Continental Cross Contact AT on my defender. I think I'll keep it that way :)

Yeah it does seem to be the Toyota/Nissan crowd doing most of the lift kit thing...not sure why that is...;)

[frantic]

Even with the lift kit won't the differential ground out first in most instances anyway? I think unless your rock crawling the lift thing is pointless...I saw a Patrol (with ridiculous lift kit) take a corner today and the wing mirror was nearly touching the ground!

I have the standard 235/85 16R Continental Cross Contact AT on my defender. I think I'll keep it that way :)

Yeah it does seem to be the Toyota/Nissan crowd doing most of the lift kit thing...not sure why that is...;)

Basically anything bigger than 33in won't fit in a patrol or landcruisers wheel.arch. So to fit 35-37in tyres they need 4 to 6 inch suspension and 2 in body lift. Whereas with a defender you can put on 35-37 with 2in lift and a small trim around wheel arches plus flares.A rrc looks great with 3-4inch lift and 35in tyres.

[MrLandy]

On a 4WD, wide tyres are just for looks. On a formula 1 car they are for on road grip.

The best tyres for 4WDing in ALL off road circumstances are tall and narrow. It's all about minimising frontal resistance, whether on sand, mud, rock.

On rocky roads, tall tyres with flat sidewalls = more clearance and less chance of puncture; In mud the same and they cut through instead of sliding on top.

In sand most people think wide is better, but they're wrong. Wide tyres have more frontal rolling resistance. If you think about it, when you let air out of tyres for sand driving, a wide tyre will bag out even further widthways making frontal resistance greater - wider footprint, pushing sand like a bulldozer; whereas a tall narrow tyre will bag out more lengthwise comparatively, creating a caterpillar track - longer narrow footprint.

All terrain tyres are a compromise between chunky mud biting tread and smooth highway grip tread. Unless you're doing serious mud driving or formular 1 racing in your Landy, your Conti ATs are perfect. 7.5R16's are the classic tall narrow size for a reason. 235/85R16's are just slightly wider for on road grip and just as tall in the sidewalls for ground clearance.

I run Bridgestone 661 AT's in 235/85R16, because they are among the few that have 10 ply sidewalls, so are very puncture resistant. They also have an excellent tread compromise, are quiet on highway and good grip in the wet. I get 60K - 80K km's out of them.

The only reason I would do a spring lift is if you had a really heavy winch and bullbar and you are going to be carrying big heavy loads for extended periods. Lifting makes the vehicles centre of gravity higher, which is bad news for stability as you've identified. I would never lift for clearance, only weight carrying. (The weight lowers springs back to standard ride height) standard Defender springs are tried and true. Lifting also creates driveline geometry problems.

Incidentally, a fully loaded roof rack full of spare tyres, jerry cans, big storage boxes and gas bottles also greatly raises centre of gravity decreasing stability, not to mention being extremely dangerous. In hard braking situations gas bottles and Jerry cans become missiles and in rollovers they can explode. Keep all weight down low.

Hope this helps. I think you've made the right decision.

[Slunnie]

Subaru Outback. 205-215 AT tyres, low CoG, same ground clearance underneath as a Discovery. Reading this thread, it might be worth considering.

[Jeff]

I disagree with Mrlandy, they are not just for looks. I have a set of 33/12.5-15 Mud Terrains that I use for fun and a standard set (well two) for the rest of the time. The wide tyres are good in ruts where you don't want your body hitting the sides of the ruts, and most of the tracks I use have been torn up by people with big tyres, so small tyres get stuck in the holes. As for not needing lift, that depends on your purpose, many on the forum have lifted Defenders and they are way more capable in the terrain around Sydney than standard Defenders.

As for extra fuel use, I drive differently with the muddies on as I don't want to wear them out on the road, so drive more conservatively and haven't noticed much difference.

Basically it depends on your use, some compare to the army, where everything is chosen on the cheapest bid, or farmers, again who don't like spending money on a work vehicle, and when it is too wet to get around they resort to a quad, with fat tyres.

Jeff

:rocket:

[Disco Muppet]

Subaru Outback. 205-215 AT tyres, low CoG, same ground clearance underneath as a Discovery. Reading this thread, it might be worth considering.

Yeah but does the army use them? :D

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[tact]

"Big tyres" can mean taller or wider, or both. Most negative comment so far is on wider tyres. Maybe that's fair in some aspects.

For off-road purposes, anything more than gravel roads, gentle greenlaning, an extra inch or two clearance to the diffs is a good thing. Taller tyres do that where lifts (body/suspension) do not.

Thing is - it is hard to get taller without also going wider. (Likely there is some limit to high aspect ratios when it comes to safety etc.

So given that "taller" is to a degree good (regards most "real" off-road activity) and that "taller" usually comes packaged with "wider" as part and parcel - careful branding all "big wheelers" as posers.

For example. My factory fitted 235/85/16 conti's are soon going to need replacing. I certainly value an extra inch or so clearance for my diffs for the kind of (not hardcore) off-road trips I do here in Malaysia.

So I am seriously considering 255/85/16 replacements for the currently fitted 235/85/16 tyres. Naturally such tyres are also wider. (Though aspect ratio is the same)

My needs mean modest increases in tall/width. Maybe not enough to be considered "poser" and "big" tyres? It is as far as I want to go despite 33" wheels being pretty much minimum spec here, for normal off-roading, and 35" more common.

[Disco Muppet]

The biggest con of larger tyres is you forever have to listen to people bitching about how you obviously are a poser who likes destroying tracks, by small minded people with small tyres who do more track damage when driven incorrectly ;)
Sincerely
A lifted 4WD owner with larger than stock tyres (and going larger)
Gotta run, have an opportunity to roll my car and pose some more :D

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[PhilipA]

IMHO it is a bit of a zero sum game.
So you're on this track and see a nice mud puddle up ahead, so you gun through it. Feel top of the world.
Then someone comes along with tyres 1 inch bigger than yours and guns through. So you come along and guess what? You get stuck in the middle of the bog!
So then you HAVE TO get larger tyres so that you can again gun through the bog, ignoring the fact there is a bypass road around the bog.
AND SO ON.

Larger diameter tyres have a better angle of attack on rock steps and can be aired down more without losing ground clearance, BUT unless this is all you do with your car there are lots of downsides.

Your gearing on the highway is now way out, so no problem fit low ratio diffs.
You now are breaking axles regularly. No problem fit HD axles.
You now break CV joints regularly. No problem etc.
In the search for ever larger tyres , you now need a 4 inch lift and body lift. No problem just spend some more money.
You now have big tyres on at low pressures and you bend all your steering rods and break the tie rod ends. No problem etc . the power steering can no longer cope so you fit a full hydraulic ram steering. No problem etc.

You now have a $10K car that you have "invested" $50K into and it is still worth $10K or less and drives like a pig on anything but gnarly trails.
Regards Philip A

[Slunnie]

Thats it!

My next set of tyres are going to be space savers.

I want performance! :mad:

[MR LR]

.

That's a very... original, username, around here :angel:

[MrLandy]

That's a very... original, username, around here :angel:

Cheers brother.

[MrLandy]

..there you have it Paul200, fat tyres are for those who want to get through tracks that those with fat tyres have pointlessly wrecked before them. Awesome.

[Rick122]

Unfortunately, it seems the "tread lightly" and "4wd is there to get me out of trouble, not into it" mentality is disappearing. In its place is 4WD Action magazine and it's various spin-offs. They like to say they are of the former statements but I don't you can even get a look the mag unless you have at least 150kw, a 4" lift and 33's (and the mandatory sand-trax bolted to the roof rack ;))
"With the power of a modified twin-turbo v8 and 35" mud terrains, rooster tails are a common sight " has become a fairly common sentence in the mag.
Cars are cheap now, especially on the second-hand market we are spoiled for choice. Power outputs of modern turbo diesels have doubled from the old oilers. Large tyres are cheap and there is a huge choice. Lift kits to fit those tyres are common and relatively cheap. And let's be honest, large tyred and lifted 4x4's look tough. For some that is enough convincing and the credit card won't get a break until that 4WD Action look is achieved. Whether that look makes the car worse to deal with on a day to day basis is not a factor for some people. 30 years ago you could drive your average 2wd family sedan out onto the beach with no worries, nowadays, as has been mentioned, unless you have massive tyres you are at the mercy of previous and following 4wd' s piloted by the non-caring individuals. Not all people are like that and I like to think the majority of Landy owners lean into the "looks come secondary to function" group. Anyway, that's enough of my rant for a Sunday and I think I've gotten carried away from your original question.
Others have stated the pro's and con's of going to larger tyres. Slightly larger will only need slight mods and compromise, going a lot bigger will require a lot of mods and compromise.
Cheers.

[Eevo]

so, going by this thread, how could i improve upon my tyres

285/60 R18 on a d2

[tact]

..there you have it Paul200, fat tyres are for those who want to get through tracks that those with fat tyres have pointlessly wrecked before them. Awesome.

Presumably you are referencing PhilipA's comments.

Notice he starts off pretty spot on with:
"So you're on this track and see a nice mud puddle up ahead, so you gun through it. Feel top of the world"

Then... the guy with bigger wheels comes along and then you need bigger tyres.. etc.

I think this bears a strikingly likeness to reality... regardless the size and type of rubber its the nut that holds the steering wheel thats at fault.

[tact]

On rocky roads, tall tyres with flat sidewalls = more clearance and less chance of puncture; In mud the same and they cut through instead of sliding on top.


Without damaging the trail of course.

[isuzutoo-eh]

I reckon the ideal is a set of narrowed Mini-Moke rims and the gnarliest studded and ribbed rubbers available to fit (in strawberry flavour), bolted to Gerlinger straddle carrier (google it!) chain drive drop-boxes, of, say 10' drop... That'd look sick mate when cruising Woolworths, and almost fit under the Maccas drivethrough roof. Could paint the drop boxes ARB ****** red and put stickers on them for added bro-points and courage.

Either that or a tall narrow tyre, ideally 100% profile, that when on reduced pressure forms a long caterpillar-like track pattern.

Yesterday my 255/85/16 (33" dia) shod County sat on her diffs a few times on rocks that those running 35s scraped but didn't pause on. If I was driving my smaller dia tyred Perentie i'd have been winching off several obstacles. As it was I needed to be dragged through one section. Whether on rocks, clay or puddles, not once did the 'skinny' tyres lack traction when clearance wasn't a problem. 9.00x16s are in my dreams...

Oh, and for those who think suspension lifts are redundant, I hit a trailing arm bracket on one rock shelf and another bloke hit a sill tank, both could have been avoided with Nissan style 6" suspension lifts. Never going to happen on my Land Rovers though!

[Rick122]

What you have described is how things have changed from having a 4wd for necessity to it being a sport. If you are quite happy to have something that tows well and can get you to your favorite fishing spot then there's little need for massive tyres and associated lifts. If however you want to play in the rocks and mud as a sport, then be prepared to spend a lot on your fourby to keep up with those that can afford to go bigger. Or become expert at recovery.

[rick130]

What you have described is how things have changed from having a 4wd for necessity to it being a sport. If you are quite happy to have something that tows well and can get you to your favorite fishing spot then there's little need for massive tyres and associated lifts. If however you want to play in the rocks and mud as a sport, then be prepared to spend a lot on your fourby to keep up with those that can afford to go bigger. Or become expert at recovery.


And that's the way it's always been.

[tact]

Bog standard 235/85/16 tyres "cutting through" thick mud down to more solid base. Note: mud depth was in places deeper than axle height - see the troweling effect of the axles/diffs leaving smooth leveled/scraped mud in front of the vehicle as it reversed back.

Track damage?

[Rick122]

This is worth a read. Some good info on tyre selection in general.
http://www.outbackcrossing.com.au/FourWheelDrive/Truth_About_4WD_Tyres.shtml

[MrLandy]

Bog standard 235/85/16 tyres "cutting through" thick mud down to more solid base. Note: mud depth was in places deeper than axle height - see the troweling effect of the axles/diffs leaving smooth leveled/scraped mud in front of the vehicle as it reversed back.

Track damage?

Umm the 'track' looks pretty stuffed already, lucky he's got narrow tyres.

[MrLandy]

This is worth a read. Some good info on tyre selection in general.
The Truth About 4WD Tyres (http://www.outbackcrossing.com.au/FourWheelDrive/Truth_About_4WD_Tyres.shtml)

Thanks Rick122, sage advice.

[DiscoMick]

Bog standard 235/85/16 tyres "cutting through" thick mud down to more solid base. Note: mud depth was in places deeper than axle height - see the troweling effect of the axles/diffs leaving smooth leveled/scraped mud in front of the vehicle as it reversed back.

Track damage?

Fat tyres would just spin and sink on that. Narrow is the go in mud.

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[MR LR]

Fat tyres would just spin and sink on that. Narrow is the go in mud.

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Unless the mud is relatively deep and bottomless, such as that found on farms after lots of rain...

[Slunnie]

Cutting through to the firm stuff would have me at about door handle depth.

Fat Simexs are the only tyres that go through here after it gets wet.

https://www.aulro.com/afvb/images/imported/2015/06/1042.jpg

[Rick122]

Really thick, sloppy mud is about the only place that wider tyres do better than skinny and then an aggressive tread pattern helps too. Maybe on soft sand a wide tyre is beneficial also but then you don't want mud tyres. A skinny but high profile tyre aired down will increase the contact patch (length, not width) and they do just as well.

From what I have been reading on other sites, the consensus is large diameter but relatively skinny, like the 235/85's or 750r16's are the best for most situations.
This is also a good (but time consuming) read.
http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html

Again, it's my opinion, I'm not here to tell anyone they are a fool for fitting huge tyres, it's a personal choice. I just have a thing about those 300kw monsters on 37's with dual diff locks plowing up what used to be good tracks.

[MrLandy]

Really thick, sloppy mud is about the only place that wider tyres do better than skinny and then an aggressive tread pattern helps too. Maybe on soft sand a wide tyre is beneficial also but then you don't want mud tyres. A skinny but high profile tyre aired down will increase the contact patch (length, not width) and they do just as well.

From what I have been reading on other sites, the consensus is large diameter but relatively skinny, like the 235/85's or 750r16's are the best for most situations.
This is also a good (but time consuming) read.
Expeditions West: Tire Selection for Expedition Travel (http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html)

Again, it's my opinion, I'm not here to tell anyone they are a fool for fitting huge tyres, it's a personal choice. I just have a thing about those 300kw monsters on 37's with dual diff locks plowing up what used to be good tracks.

Agreed. Very well said Rick. Cheers

[tact]

[...]I just have a thing about those 300kw monsters on 37's with dual diff locks plowing up what used to be good tracks.

Totally agree with you on that!

In Malaysia we sometimes come across real idiot cowboy types who weld up their diffs, have twin turbo petrol engines that they drive constantly up where bouncing valves are the default rev limiter... and they rape the landscape the way they drive.

At times these idiots get trails closed off by indigenous people (Orang Asli). As the jungles are the environment where the OA live, work and play. Decent offroaders appreciate this and appreciate being allowed, or even welcomed, by the OA where others are shut out.

[Slunnie]

I disagree.

Personally, I think 7.50s do absolutely nothing well in comparison to a modern tyre except that they have a thicker stronger carcass. They don't grip the road well, they don't grip trails well, they dont grip rock well, they don't air down and retain stability when cross sloped and I don't think they particularly do mud well. They do cut through everything well though, because they're skinny.

Also, all tyres lengthen their footprint when they air down, and they all bag in the sidewall. Previous comments suggesting that wide tyres get wider and skinny tyres get longer is absolutely incorrect and patch testing has shown this to be the case.

Likewise on sand, yes a wide tyre does work better because you can get better floatation off it. As a skinny is aired down to increase the footprint, so does a wide tyre, except with greater floatation, so they're not sinking in as far. But, the tread pattern also makes a difference. Lots of edge creates drive in the sand but also digs faster. From my experiences, HT's wont drive you as well in the sand, but if you don't know when a tyre is spinning then they wont dig you in as quickly. Other extreme, a Simex will provide a heap of drive and it will judder when you start to dig down, but as some may think, you wont hit China before you know whats going on. I recall going to Fraser on Simex and some bloke laughed and told me to have fun digging. At this stage most vehicles couldn't get through Ngarla, yet I was able to drive around them (Yes, I was helping to recover until an unhelpful lard drove in and sunk it to the belly without helping others and now himself to get out)! That said, the best tyre I think I've seen in the sand is the Procomp AT in a 315/75-16, now this tyre has lots of edge!

There is a lot perpetuated on here, and it doesn't mean it's correct.

[MrLandy]

"...all tyres lengthen their footprint when they air down, and they all bag in the sidewall. Previous comments suggesting that wide tyres get wider and skinny tyres get longer is absolutely incorrect and patch testing has shown this to be the case." I'd like to see the evidence of that Slunnie...

[Rick122]

I disagree.

Personally, I think 7.50s do absolutely nothing well in comparison to a modern tyre except that they have a thicker stronger carcass. They don't grip the road well, they don't grip trails well, they dont grip rock well, they don't air down and retain stability when cross sloped and I don't think they particularly do mud well. They do cut through everything well though, because they're skinny.

The 750r16 I quoted was just an example of a skinny but high profile tyre that Land Rover's have used and we can relate to. Nothing more should be read into that, I've only experienced them on a perentie off road and that did not include any real deep mud or sand.


There is a lot perpetuated on here, and it doesn't mean it's correct.
Yep, you said it. Which is why I included links to some external articles so people can make up their own mind. It would be good if you could provide some links to support your argument against skinny tyres other than just personal experience.

[Slunnie]

The 750r16 I quoted was just an example of a skinny but high profile tyre that Land Rover's have used and we can relate to. Nothing more should be read into that, I've only experienced them on a perentie off road and that did not include any real deep mud or sand.


Yep, you said it. Which is why I included links to some external articles so people can make up their own mind. It would be good if you could provide some links to support your argument against skinny tyres other than just personal experience.
Likewise I have spent time in Perenties also and my opinion isn't particularly good. This is in part due to the tyres they have, the pressures they run and the load carrying spring rates which they are made with. The vehicle itself however is very good.

If websites are what justify experience, as opposed to the opposite, then my website is at www.slunnie.com - Aussie Built Rovers (http://www.slunnie.com)

[Slunnie]

"...all tyres lengthen their footprint when they air down, and they all bag in the sidewall. Previous comments suggesting that wide tyres get wider and skinny tyres get longer is absolutely incorrect and patch testing has shown this to be the case." I'd like to see the evidence of that Slunnie...
An example:

Beadell Tours - Tyre Footprints by Mick Hutton (http://www.beadelltours.com.au/tyre_footprint.html)



Goodyear Wrangler RT/S ? 265/75R16LT ? 10 Ply (original fitment on F250s)
MRF M77 ? 7.50-16 ? 14 Ply

https://www.aulro.com/afvb/images/imported/2015/06/915.jpg

[Rick122]

So in that picture the 750r16 (aprox 190mm width) has almost the same footprint width and length when aired down to 20psi and not much less length at 10psi as the much larger, 40% wider 265/75r16. That's interesting. I would have thought a bigger difference. The tread blocks are a lot chunkier and spaced out on the old 750/16 though.

[Chops]

A good read, thanks for all the info input guys.

Of course this just means I'm even more confused as to what to get next :(

[Slunnie]

So in that picture the 750r16 (aprox 190mm width) has almost the same footprint width and length when aired down to 20psi and not much less length at 10psi as the much larger, 40% wider 265/75r16. That's interesting. I would have thought a bigger difference. The tread blocks are a lot chunkier and spaced out on the old 750/16 though.
Treadfaces on those particular tyres are similar, the next carcass width down (235/245 etc) would be about the same. The variation in length is due to the rigid construction of the MRF. The MRF at 10psi is similar to the GY at 20psi, but pressures for a given footprint will vary due to load, tyre construction etc so despite it being a pressure based comparison, it probably should be in practice a footprint length comparison - but thats not as interesting. :lol2:

[MrLandy]

Thanks Slunnie, interesting that footprints appear similar, however there is clearly less bagging widthwise in the 7.50R16... Meaning less frontal resistance especially in sand...

[MrLandy]

...than 265/76R16. These sidewalls would push far more sand than the tall ones of the 7.50R16.

[Rick122]

Treadfaces on those particular tyres are similar, the next carcass width down (235/245 etc) would be about the same. The variation in length is due to the rigid construction of the MRF. The MRF at 10psi is similar to the GY at 20psi, but pressures for a given footprint will vary due to load, tyre construction etc so despite it being a pressure based comparison, it probably should be in practice a footprint length comparison - but thats not as interesting. :lol2:

Which supports the theory that if there is little difference between skinny and wide tyres when aired down, then there is little reason to go to a bigger tyre when there are so many more compromises to be made. Each to their own.

[B.S.F.]

In that picture the comparison is between a 10 pr Radial and a 14pr Cross ply.

[Slunnie]

Thanks Slunnie, interesting that footprints appear similar, however there is clearly less bagging widthwise in the 7.50R16... Meaning less frontal resistance especially in sand...

Both have the same rim diameter and the same tyre diameter. If aired down to the same footprint length the bag will the same - sidewall rubber cant be made or disappear. The 7.50 is a much heavier carcass, so airing down to a given pressure will not give it the same footprint length and that can be seen in the picture I posted, the wide tyre actually had a much longer footprint and so bagging is greater. It however is footprint you are after for floatation in the sand, not the tyre pressure, so the sidewall bagging will be the same for the same length.

This is looking at it one dimensionally though. Because of the reduced ground pressure from the wider tyre, you will also find it is not sitting as deeply into the sand as the skinny one.

[Slunnie]

Which supports the theory that if there is little difference between skinny and wide tyres when aired down, then there is little reason to go to a bigger tyre when there are so many more compromises to be made. Each to their own.

I think thats unique to the tyres that happen to have been used. Thats the widest 7.50 I've ever seen and its absolutely abnormal for them to be comparable in width to a 265/75-16! But a footprint isn't the whole story when offroad, there is also carcass stability etc etc etc.

[tact]

Umm the 'track' looks pretty stuffed already, lucky he's got narrow tyres.

The lucky "he" with the narrow tyres is me. And that's my 110DC in that pic.

The fler with the big wide muddies in this pic had no issues in the same mud coincidently. (Oh look my little 110 is in the background)

The fler in the pic with the REALLY skinny tyres (both of them) was the one having real difficulty..... :D

[tact]

Fat tyres would just spin and sink on that.

The post just above this with another pic of a fler with big wide muddies in the same slop... Didn't go down as you opined.

Just sayin'...

(Not saying the big fat tyres are better)

[tact]

Really thick, sloppy mud is about the only place that wider tyres do better than skinny and then an aggressive tread pattern helps too. Maybe on soft sand a wide tyre is beneficial also [...]

The ONLY place? You actually suggest soft sand too... So there are only TWO places where wider is better?

I would add another scenario - In my experience wide tyres also work better on hard packed greasy slippery clay where you don't dig in at all. Both wide and narrow tyres spin on the surface rather than dig in. Wider tyre has more points of contact with the surface and with appropriate throttle control can make progress when narrow rubber struggles.

In the Antarctic we also ran wide AT tyres on the hiluxes and they worked well on ice and snow.

[tact]

Since "without pics it didn't happen" is a meme here:

All three of these vehicles with chunky, wide, open, aggressive tread patterns would spin all 4 wheels if you are gruff on the throttle on soft snow or on blue ice so slippery you find it hard to stand upright even when sober.

However all 3 will also find traction and get mobile even on blue ice if you are sensible with the throttle.

[tact]

As above

[Rick122]

How good of you to pick parts of my post to use as the full basis of your argument. Maybe we should list every scenario you could possibly encounter giving the pro's and con's of each tyre, and then list every tyre available and rate it against each scenario. Don't think it's going to happen. You like big tyres and are prepared to live with the compromises, good for you.

[tact]

As above again. (Can't attach 3 pics to one post using iPad apparently)

[DiscoMick]

Isn't the length more important than the width with bigger tyres?

[Disco Muppet]

How good of you to pick parts of my post to use as the full basis of your argument. Maybe we should list every scenario you could possibly encounter giving the pro's and con's of each tyre, and then list every tyre available and rate it against each scenario. Don't think it's going to happen. You like big tyres and are prepared to live with the compromises, good for you.

Not like the 'big tyres are for *******' brigade doesn't do the same thing. In fact, I find that camp to be far more aggressive. :rolleyes:

Sent from my HTC One using AULRO mobile app

[tact]

How good of you to pick parts of my post to use as the full basis of your argument. [...]You like big tyres and are prepared to live with the compromises, good for you

Sorry you feel hard done by. Wasn't selectively quoting you to do you or your case harm. Just focusing on what was relevant. You wrote what you wrote. There is no backing away from that.

Something is either "about the only place" or its not.

And: no, I am not a proponent of "wider is better". Thought I have been careful to make that clear.

I am against people saying "narrower is better nearly all the time" or the mirror of that - "this one or two scenarios are the ONLY places where wide might be useful".

[Disco_Fever]

Hi all,

I see a lot of 4WDs in Australia with large tires and lift kits etc...

Does installing big tires and lifting the suspension have much impact on the fuel economy? I know it must have some but has anyone ever measured it?

Another thing I have observed is that the military don't install all this stuff on their vehicles which makes me wonder whether it actually increases off road capability much? Are all these lifted 4WDs with big tyres just poser cars?

Anyway, to help the original poster...

My td5 disco 2 came with a set of 265/75 16 muddies, which now almost all the time are replaced with 255/60 18 ATs.
There is a noticeable change in fuel economy and response - and would guess could affect mechanical longevity if kept on long term.

You can get a manual td5 disco to the top of Billy Goat's Bluff on stock 29" HTs... but they will be ripped to shreds after. A set of ATs or similar will cop the abuse for much longer.

In my experience, mechanical and environmental sympathy are at least (if not more) important than tyre size.

Sent from my SM-G900I using AULRO mobile app

[tact]

Isn't the length more important than the width with bigger tyres?

Traction is important.

How much traction is available varies for a lot of factors like: the surface of the road/ground, wet/dry, soft/hard, the tyre's rubber compound, tyre pressures, tyre size, vehicle weight etc.

If we say for any vehicle many of those factors are a constant. i.e. a vehicle won't change weight, tyres, in the blink of an eye: then the variables are simpler, largely just ground/trail condition and tyre pressures (size of contact patch)

Now let's just hold the ground/trail condition and tyre pressure (contact patch size variation) as constants for a bit too.. Loosely... And change one of the earlier fixed parameters: the size of the tyre.

A tall narrow tyre, aired up, will have a certain length and width of contact patch. Let's say it's a 6" tyre. However long the contact patch is (adjusted by tyre pressure) largely the WIDTH of the contact patch will not change. 6"

A tall wide tyre, aired up, will have a certain length and width of contact patch too. Let's say it's a 10" tyre. However long the contact patch is (adjusted by tyre pressure to match the LENGTH of the 6" wide tyre) - the WIDTH will still be 4" wider than the 6" tyre

No question. No room to move. In this scenario the area of the contact patch for the wider tyre is larger (I.e. length X 10" is a larger patch than length X 6" ).

Does this matter? Of course it matters anywhere that there is any traction to be had on a reasonably firm surface. From tarmac to blue ice.

On soft surfaces. Soft sand. Soft mud. Other factors kick in. Things like how deep into the surface the tyre sinks. Every added millimeter depth adds to the length and relative steepness of the perpetual and virtual "ramp" the tyre has to constantly run up while making forward progress. Until underbody grounds and no one is going anywhere.

Does wide or narrow perform better in soft conditions? You decide for yourself. I have seen and used both wide and narrow tyres in soft conditions and don't see a lot of difference.

On any firm surface where by definition there is no "digging in for more traction" No contest. Wide

[MR LR]

Narrow tyres are best, eh?

I guess that's why tracks are so narrow...

https://www.youtube.com/watch?v=P4RmS_xkszU

[tact]

One of the common arguments trotted out by those who stick to old chestnuts like "narrow tyres are always (or nearly always) better than wide" is the formula that says
"Contact patch area = weight / tyre pressure"

This formula leads to thinking (popular teaching in science/engineering classrooms) that says wide or narrow makes no difference - Contact patch will be the same if vehicle weight and tyre pressure are equal.

(Of course in my previous comments I talked about unequal tyre pressures. Specifically: adjusting the pressure in the wide tyre (lowering it) to match the LENGTH of the narrower tyre's contact patch... The wide tyre patch is still wider thus greater contact area)

So let's now tilt the equation back to equal pressures. Same contact patch area according to the formula. Which begs the question: if the contact patch is the same why do the narrow pundits say a narrow tyre better? Doesn't this (same contact patch area) put the lie to the argument that a narrow tyre has a smaller contact patch which means higher ground force down on that patch to give better dig down ability and higher traction to boot because more load on a smaller area means better traction... (Breathless!)

C'mon... You can't have it both ways. Ok the narrow tyre pundits who are clever then avoid a fight that can't be won. Yes, contact patch is the same. Vehicle weight is the same. So ground force is the same, traction is the same... Static traction.

This then leads to comments like - "BUT....!":
- while the contact patch area is the same there is still a difference. The patch is wider than long in a wide tyre. Good for lateral (sideways) forces. The narrow tyre patch is longer than wide. Better for traction in the straight line where it's more needed. (They will argue)
- and... If the wide tyre were to be aired down to increase contact patch area: Available friction is not related to contact area as the weight is spread across a greater area and so no improvement in traction. (They will argue)

And maybe if the formula holds true... And if physics classes are all spot on in the theories... Narrow tyre pundits win. Narrow is better. Maybe.

What if the theory was bollocks? All the above "narrow is better" logic falls apart and some better understanding of why the reality we observe on the race track and in the jungle (i.e. that wider tyres do just fine thank you) seems to run counter to the classroom wisdom.

How would someone empirically determine whether the theories are bollocks? Real testing?

Devour this:
Fact or fiction? Tire contact patch size is determined mostly by weight and tire pressure. | Performance Simulations (http://www.performancesimulations.com/wp/fact-or-fiction-tire-contact-patch-size-is-determined-mostly-by-weight-and-tire-pressure/)

[tact]

Just to be a fungi and poke fun at one eyed comments in general:

Anyone here want to say hi lift jacks are dangerous and no one should use them? :cool:

******* with big tyres and lifts would need one for whenever the barge gets a flat at the mall car park...

[tact]

Hi all,

I see a lot of 4WDs in Australia with large tires and lift kits etc...

Does installing big tires and lifting the suspension have much impact on the fuel economy? I know it must have some but has anyone ever measured it?

Another thing I have observed is that the military don't install all this stuff on their vehicles which makes me wonder whether it actually increases off road capability much? Are all these lifted 4WDs with big tyres just poser cars?

I tilted at this in some of the many lengthy posts in this thread already... But just to bring it to focus for you...to answer part of your question:
Bigger tyres are one of the few things (mods) that will increase ground clearance to axles/diffs. (Another would be fitting portal type axles)

More ground clearance does make an improvement to off-road capability (not getting hung up on obstacles so much). Of course this is NOT needed, and truly a ****, for those who's off-road excursions are limited to the local mall car park.

It's just a fact of life that beyond certain vehicle specific limits larger tyres can mean lifts and other work may be needed.

I do want a bit more ground clearance for my driveline. Trails I drive have already seen me dragging diffs over rocks and damaged all my side steps (so I removed them - see pic, still with stock 235/85/16 tyres).

My intention is to only go as large (tall) as I can without doing any lifts. So I think research says max is 255/85/16 for a 2013 Defender. That's what will be my next tyre around end of this year.

Sorry I cannot respond to the fuel economy question - never collected that data myself.

[goingbush]

My current truck is the heaviest vehicle I've owned, well excluding my old Acco 4x4.

Its got the widest and also the tallest tyres Ive ever had , at 37" x12.5R17 - I guess I'm a ****** then !
a hi Lift jack no good to me, it won't fit under the truck !

yet its by far the most capable 4x4 vehicle I've owned, by a long shot .

How much better a Defender is than an 80 series off road, multiply that again and its how much more awesome this Daily 4x4 is off road than the Defender , in any situation, Especially Loaded and in sand - and the tyres are MT's

so how does that work ??

[MrLandy]

Its simple. A wider tyre has a wider contact patch. Therefore more frontal resistance.

[Jeff]

Why are the narrow tyre nazis even in 'The Modified Zone'?

Jeff

:rocket:

[Tombie]

Why are the narrow tyre nazis even in 'The Modified Zone'?

Jeff

:rocket:


Because you can have narrow tyres with large rolling diameter :cool:

Larger rolling diameter plays a reasonable part in capability regardless of width... :cool:

[tact]

Its simple. A wider tyre has a wider contact patch. Therefore more frontal resistance.

Can you reference any studies on how much impact this really has?

The best explanation I ever saw regards wheels in soft terrain likened what's happening to there being a small virtual "ramp" constantly in front of tyres. The length and angle of the ramp being a function of how deep the tyres sink into the ground, the rolling radius of the tyre.

Not the same calculations in every case - as the calculations that would be needed in a model that assumes the tyre is "pushing through" the medium. (Though this works for media like water, really sloppy mud)

Obviously tyre width has little impact on the tyre climbing a ramp.

[tact]

I cannot find a reference to the "virtual ramp" model for tyres on soft ground (as opposed to models that imagine tyres in soft ground are like bulldozers... Where pushing a wider blade (tyre) means harder work- so narrower tyres are better). But it was something like 20yrs ago I read it. Sorry.


I did find this though...
http://ethesis.helsinki.fi/julkaisut/maa/mvaro/publications/31/appendix7.pdf

On about page 7 of the thesis found here, you find the diagram in the pic attached below. The diagram illustrates what I was describing. The deeper the depression obviously the more work to overcome.

Mr. Land Rover would postulate that for any fixed depth the "frontal resistance" is greater with a wider tyre. That's likely right and applicable if both the wide and narrow tyre sink to the same degree on the same ground.

They don't. Of course. In reality. (Unless we are talking watery slop)

Narrow tyre pundits (avoiding the "nazi" term someone else used! :twisted: for those who maintain that narrow is (nearly) always better) are always quick to point out that the narrow tyre does in fact "dig down" better to find traction if there is a solid bottom to the trail.
- Of course this is only useful if there is a solid bottom
- and they argue the wide tyre doesn't manage to dig that deep and find the solid bottom. (If it did - no point in making this "narrow digs down better" point and narrow is no better than wide if both find that nice solid bottom)

So at least we agree that wides do NOT sink in as deep as narrows. And that's the point: while wide tyres have a wider frontage - those ditch digging narrows go deeper.

What is harder to roll out of? A wide shallow hole or a narrow deep one? Which has the higher "frontal resistance"?

I am sure I don't know. But I have seen and driven both narrow and wide on soft stuff and don't see a lot of difference. (As said before in words and pictures in this thread)

I guess I could go out on a limb and state that in conditions sloppy enough that both wide and narrow tyres did find a bottom at the same depth (water or really sloppy mud - else the wide tyre won't sink as deep as the narrow) - then the wide tyre's greater frontage would certainly make for harder going... So good luck all you wide tyre ******* getting through a few feet of water(or equivalent!). :wasntme:

[n plus one]

Hi all,

I see a lot of 4WDs in Australia with large tires and lift kits etc...

Does installing big tires and lifting the suspension have much impact on the fuel economy? I know it must have some but has anyone ever measured it?

Another thing I have observed is that the military don't install all this stuff on their vehicles which makes me wonder whether it actually increases off road capability much? Are all these lifted 4WDs with big tyres just poser cars?

I'm hesitant to wade into this ****uation, but what the heck.

To the OP, put a modest (2 inch) lift and slightly larger than standard (255/85) tyres on my Defender and experienced a noticeable improvement in offroad performance, particularly on more challenging tracks. Improved performance included a (perceived) increase in traction, reduced diff dragging and better body clearance to the trail.

The cost to on road performance has been minimal and a worthwhile trade off for my intended use - YMMV.

Hope this helps.

PS in the interests of keeping the pot stirred I'll leave the room on this note, why does a comp rig have better offroad performance than a stock 4wd? :angel:

[MR LR]

PS in the interests of keeping the pot stirred I'll leave the room on this note, why does a comp rig have better offroad performance than a stock 4wd? :angel:

Because of all the stickers on it! Duh! :wasntme:

[Rick122]

Seriously, I think the narrow vs wide tyre argument has been done to death. If you search Google there are pages upon pages of forums from all over the world that have all had the same discussions as us going back years. I stumbled upon this article which is well written and makes a lot of sense yet doesn't cover all situations as it's mainly about sand driving. Although this will probably spark up the debate again lol..:o

http://outbackjoe.com/macho-divertissement/macho-articles/why-wide-tyres-dont-help-in-sand/

[Slunnie]

Seriously, I think the narrow vs wide tyre argument has been done to death. If you search Google there are pages upon pages of forums from all over the world that have all had the same discussions as us going back years. I stumbled upon this article which is well written and makes a lot of sense yet doesn't cover all situations as it's mainly about sand driving. Although this will probably spark up the debate again lol..:o

Why Wide Tyres Don't Help In Sand | outbackjoe (http://outbackjoe.com/macho-divertissement/macho-articles/why-wide-tyres-dont-help-in-sand/)

This picture below immediately falsifies the article in that link.


An example:

Beadell Tours - Tyre Footprints by Mick Hutton (http://www.beadelltours.com.au/tyre_footprint.html)



Goodyear Wrangler RT/S ? 265/75R16LT ? 10 Ply (original fitment on F250s)
MRF M77 ? 7.50-16 ? 14 Ply

https://www.aulro.com/afvb/images/imported/2015/06/915.jpg

And so the wide/skinny debate wheel goes around again! :lol2:

[DiscoMick]

I think we're mixing two issues here - tyre size and clearance.
Obviously a taller tyre gives greater clearance so lets concede that one.
On traction, say in mud, the narrower tyre should sink further so more likely to find the bottom and get traction. The wide tyre shouldn't sink as much so less likely to find traction and more likely to spin.
On sand, you want to float, not sink. A wider tyre shoud float more than a narrower tyre.
Another issue is tread. A more aggressive tyre is more likely to dig down. Thats good in mud and bad on sand.
A taller tyre will have a longer contact patch. A wider tyre will have a wider contact patch and have to push more in front of it.
Is that right?

Sent from my GT-P5210 using AULRO mobile app

[Rick122]

I think we're mixing two issues here - tyre size and clearance.
Obviously a taller tyre gives greater clearance so lets concede that one.
On traction, say in mud, the narrower tyre should sink further so more likely to find the bottom and get traction. The wide tyre shouldn't sink as much so less likely to find traction and more likely to spin.
On sand, you want to float, not sink. A wider tyre shoud float more than a narrower tyre.
Another issue is tread. A more aggressive tyre is more likely to dig down. Thats good in mud and bad on sand.
A taller tyre will have a longer contact patch. A wider tyre will have a wider contact patch and have to push more in front of it.
Is that right?

Sent from my GT-P5210 using AULRO mobile app

I agree with everything you have written there.


This picture below immediately falsifies the article in that link.

Just saying something didn't make it true Slunnie. If you're going to make a statement like that you are going to actually show why it falsifies the article. As pointed out earlier, the 265 tyre is roughly 40% wider than the 750 tyre so the same should show on the paper, yes? However, the tyre widths in that picture look exactly the same, so I could say that article is completely false - based on that one fact. Anyway, happy trails.:)

[DiscoMick]

So maybe the best tyres for the two situations of mud and sand are very different extremes:
Mud- tall, narrow with a chunky tread to bite down
Sand - wide with a mild tread to float, not dig down.
So, what's the best compromise for overall use, assuming we only have one set of tyres? Maybe a tall narrow tyre to sink into mud with a mild tread so it doesn't dig holes in sand and is quiet on the bitumen?
What do you think?


Incidentally, it was interesting on our Simpson crossing trip last year that the trip leader Dave, who is very experienced and works for ARB, chose wide Cooper AT2s with a mild tread on his Patrol trayback for the sand dunes.
He went over dunes that others, including some with more aggressive tyres, got stuck on. Interestingly, Dave was strong on lowering tyre pressures to avoid getting stuck. He said he thought snatch straps and winches were only last resorts when all else failed. As a result of his guidance, our group made the whole crossing without a single use of a snatch or winch, which compared with other groups who used snatches and winches multiple times. Having the right tyres and pressures was the key, not big lifts and lots of expensive gear.
So, that was on sand. Mud might be a different story.

[strangy]

Wow, quite few posts of tedium now.
Maybe some broader considerations could have the discussion move along.

Aircraft operating regularly into unsealed or soft surfaces use wider and larger diameter tyres.
Uh oh, wider and taller??
They are often referred to as high flotation gear which can have several tonnes happily move around on surfaces that would crumble under lighter machines.

So tall skinny guys are wrong " cutting into mud sand etc" because we don't want that resistance reducing take off performance or causing the aircraft to become bogged.
Wide tyre guys are wrong too
"Wide tyres bag out more" so that's also resistance that we don't want reducing take off performance and requiring longer rwys.

So why are they used?

Because they are far better than what comes std according to the intended purpose of the equipment they are fitted to and allow the equipment and operators to do things they couldn't do normally without the mod.

It is a fact that these tyres do less damage to the very fragile( by comparison to tracks) surface that they are used on.
While they may not be asked to provide traction under power, they are required to provide under brakes.

I know what I have fitted to my vehicles suits my needs and is overkill for regular use, but so is the vehicle. Most of the population don't even need a 4WD.

It is good to know that whichever is fitted to my vehicle that I will generally be considered a "big tyre ******" or "skinny tyre never goes off road" guy.

[Rick122]

And the most irrelevant post bringing aircraft into an offroad discussion goes to...TIC
I'd also say your end statement is opposite to the norm. It should be "Big tyred, more concerned with looks than performance, predominantly seen driving in the suburbs" and "tall and narrow tyres more concerned with off road performance than looks, predominantly seen in the outback doing their job" haha.
I don't know how relevant this is now but to quote "The Rain Forest Challenge and The Trophy challenge have all been won by the aggressive Simex Trekker tyre (35x11.00).*" by all regards a very tall and narrow tyre.
Also nearly all Camel Trophy cars used 700R16. They did alright with the tall and narrow.
Anyway, have a great day people!

[MrLandy]

Hilarious thread! ...Ok, when Defenders can fly or drive on water maybe I'll consider wider tyres.

[Slunnie]

Just saying something didn't make it true Slunnie. If you're going to make a statement like that you are going to actually show why it falsifies the article. As pointed out earlier, the 265 tyre is roughly 40% wider than the 750 tyre so the same should show on the paper, yes? However, the tyre widths in that picture look exactly the same, so I could say that article is completely false - based on that one fact. Anyway, happy trails.:)
Sorry, I just thought that after reading the link that it was pretty blatantly obvious and didn't realise I had to spell it out. :D

Here is the premise that the thread hinges on.


So contact patch is dependent on force and pressure and has no regard for dimensions. What this means is at the same pressure, a narrower tyre will deform more than a wider tyre to achieve the same contact patch. Any sized tyre will deform just the right amount to achieve the contact patch described by the formula above. Lets substitute some values to see how it works.

And this picture is what shows that this premise is incorrect. You'll notice that at a given pressure the contact patches are not compensatory as the article states. Actually the wide tyre has a notably longer contact patch than the skinny tyre in addition to the extra width. The article is working off the premise that a skinny tyre will have the same contact patch as a wide tyre because it elongates more, yet the testing shown in the picture actually disproves this and the contact patch is significantly shorter an narrower than the wide tyre then it falsifies the article.

The picture below actually supports pretty strongly reasons at a technical level why a wide tyre should be much better on sand.... oh sorry, because there is a much greater contact patch and so increased ability to float and drive.

As an aside, I'm not sure what the measurements of those tyres widths are, but 7.50's are typically about 165-170mm wide at the treadface (I support this with my tape measure and a heap of 7.50's at home - Interestingly 235.85's measure at about 190mm) which is unlike the one used and I haven't seen any 235/85's with a wider tread face than a 265/75.

https://www.aulro.com/afvb/images/imported/2015/06/915.jpg

[Rick122]

Actually the wide tyre has a notably longer contact patch than the skinny tyre in addition to the extra width. The article is working off the premise that a skinny tyre will have the same contact patch as a wide tyre because it elongates more, yet the testing shown in the picture actually disproves this and the contact patch is significantly shorter an narrower than the wide tyre then it falsifies the article.

As an aside, I'm not sure what the measurements of those tyres widths are, but 7.50's are typically about 165-170mm wide at the treadface (I support this with my tape measure and a heap of 7.50's at home - Interestingly 235.85's measure at about 190mm) which is unlike the one used and I haven't seen any 235/85's with a wider tread face than a 265/75.

Actually it's this picture which I would be disputing for the above reasons. There is no way that 265 tread pattern is 40% larger than the one below it, yet that is what it should show. So I dispute the whole article. And yet you keep dragging it out as proof.
There are many more articles out there on the virtues of a tall and narrow tyre, yet you have provided only 1 article which is obviously flawed. All that picture shows is that when aired down, the tread contact patch is almost the same, yet by your reasoning, the wide tyre should be much larger.
Yeah I'm pretty much done with it...

[DiscoMick]

Sorry, I just thought that after reading the link that it was pretty blatantly obvious and didn't realise I had to spell it out. :D

Here is the premise that the thread hinges on.



And this picture is what shows that this premise is incorrect. You'll notice that at a given pressure the contact patches are not compensatory as the article states. Actually the wide tyre has a notably longer contact patch than the skinny tyre in addition to the extra width. The article is working off the premise that a skinny tyre will have the same contact patch as a wide tyre because it elongates more, yet the testing shown in the picture actually disproves this and the contact patch is significantly shorter an narrower than the wide tyre then it falsifies the article.

The picture below actually supports pretty strongly reasons at a technical level why a wide tyre should be much better on sand.... oh sorry, because there is a much greater contact patch and so increased ability to float and drive.

As an aside, I'm not sure what the measurements of those tyres widths are, but 7.50's are typically about 165-170mm wide at the treadface (I support this with my tape measure and a heap of 7.50's at home - Interestingly 235.85's measure at about 190mm) which is unlike the one used and I haven't seen any 235/85's with a wider tread face than a 265/75.

https://www.aulro.com/afvb/images/imported/2015/06/915.jpg



So (and I'm not pretending to be an expert here, just interested) if we take two tyres which are both the same e.g. 235 and 16, but one is 70 and one is 85 (e.g. original D1 vs. Defender), and both tyres have the same tread, then isn't it right that the 85 should have a bigger (longer) contact patch, while the width would be the same?


If a tyre's contact patch is longer, but not wider, then isn't the theory that that tyre would be better in mud, but not better on sand, because in mud you want to hit the bottom but on sand you want to stay on the top?
Or have I got that all wrong?


I ask because I'm just not convinced that, in most situations, its worth spending a lot of extra money on bigger, wider tyres.

[goingbush]

Thats just wrong, whoever did those ink prints had just made images perceiving what he thought they should be, down below 20psi the contact pattern in the centre of the tyre would be very light, but its still as dark as at 50psi, at 10psi the centre would hardly be in contact with the ground at all , especially on a hard flat surface - such as you would need to make those prints. And at low pressures the outside of the tread pattern should be much darker as its pressing in harder, theory ok but execution has tripped him up. (of course on sand or mud the centre is still in good contact - but the prints weren't done on sand or mud)

[Rick122]

Yes, the higher profile tyre will deform more and the contact patch should lengthen more. Regardless what that picture shows....;)
Personally, I think that narrow tyre must have had very tough side walls, so didn't deform as much as it should have.

[MR LR]

Thats just wrong, whoever did those ink prints had just made images perceiving what he thought they should be, down below 20psi the contact pattern in the centre of the tyre would be very light, but its still as dark as at 50psi, at 10psi the centre would hardly be in contact with the ground at all , especially on a hard flat surface - such as you would need to make those prints. And at low pressures the outside of the tread pattern should be much darker as its pressing in harder, theory ok but execution has tripped him up. (of course on sand or mud the centre is still in good contact - but the prints weren't done on sand or mud)
BUT!
How do you get a print without first placing the center of the tyre on it?

[MrLandy]

Or to put it even more simply, how can a wider tyre not have a wider footprint?

[Slunnie]

Actually it's this picture which I would be disputing for the above reasons. There is no way that 265 tread pattern is 40% larger than the one below it, yet that is what it should show. So I dispute the whole article. And yet you keep dragging it out as proof.
There are many more articles out there on the virtues of a tall and narrow tyre, yet you have provided only 1 article which is obviously flawed. All that picture shows is that when aired down, the tread contact patch is almost the same, yet by your reasoning, the wide tyre should be much larger.
Yeah I'm pretty much done with it...

Its really not that hard to comprehend, especially if you actually sat down with a whole heap of tyres and looked at them, as in actually really looked at them. The only anomoly is that the 7.50 they have used has a broad tread face, and to be honest they are out there and open pattern bias ply tyres are like that as they square off the edges - The Simex which are also bias actually flare the tread blocks out to a treadface. When I look at those contact patches at the lower pressures and compare the amount of space between the patch and the top/bottom of the page, there looks to me to be a significant difference in the patch length, they are not similar at all - it highlights there that the wide tyre does have a longer contact patch. Actually the wide tyre goes off the end of the page!

[Slunnie]

So (and I'm not pretending to be an expert here, just interested) if we take two tyres which are both the same e.g. 235 and 16, but one is 70 and one is 85 (e.g. original D1 vs. Defender), and both tyres have the same tread, then isn't it right that the 85 should have a bigger (longer) contact patch, while the width would be the same?.

That's basically correct. The additional sidewall high will allow the tyre to be aired down further and increase the length of the footprint.

The other thing is that sometimes as the tyre profile drops, the treadface increases, so to take an extreme, if you compare the treadface of a 255/85-16 and a 255/60--18, you will probably find the 18's tread face is (eg) 35mm wider. This is because the width measurement is taken through the bag of the tyre, not at the treadface.

But that said, without measuring, I'd expect a 235/85-16 will put down a much larger contact patch than a 235/70-16.

[BadCo.]

Edit didn't see this thread was actually ten pages long, silly app took me too the start

[Rick122]

Its really not that hard to comprehend, especially if you actually sat down with a whole heap of tyres and looked at them, as in actually really looked at them. The only anomoly is that the 7.50 they have used has a broad tread face, and to be honest they are out there and open pattern bias ply tyres are like that as they square off the edges - The Simex which are also bias actually flare the tread blocks out to a treadface. When I look at those contact patches at the lower pressures and compare the amount of space between the patch and the top/bottom of the page, there looks to me to be a significant difference in the patch length, they are not similar at all - it highlights there that the wide tyre does have a longer contact patch. Actually the wide tyre goes off the end of the page!

I think you really should read the article again. So let me reply with quotes from the article and then summarize.
"As you should be able to see, there is little difference in footprint until you reach 10 psi."
Then he goes on to say "How could it be possible for a narrow tyre with 1950's technology on a split rim to have an almost identical footprint to a*modern wide tubeless tyre in a size renowned for floatation and 4WD ability ? bit of a surprise eh?".
And then, "I was interested to see how the sidewall flexed in both tyre constructions. I then let the pressures down to 15 psi (below), a pressure that can be needed every now and again when the conditions are wet & soft. Another time for lower pressure is climbing in steep country and also climbing very stony ground."
So he let the pressures down to 15psi, not 10 as in the first picture.
"When you look at the footprint pictures and then the above image of the Bias sidewall, you'd have to wonder why you'd use Steel Belted Radials at all in tough country with sharp bits that you have to drive over. Yes, I do realise that 15 psi is too low for normal work, but it was a good way to illustrate the difference in sidewall constructions."

So to summarize:
A) the first picture you posted shows virtually no difference in contact patch between the two tyres at 20psi, a pressure you would likely to go down to in soft sand etc.
B) At 15psi pressure the radial tyre would be at great risk of getting staked through the side wall and was too low a pressure for normal off road work. You can clearly see that in the pictures in the article, the sidewall is almost on the ground! Imagine what it would have liked like at 10psi!
C) So 10psi is the only pressure where the contact patch was bigger yet at that pressure it would clearly not be wise to run it that low. So you wouldn't run that tyre at 10psi, so it shouldn't be used as the basis for an argument saying that proves it's better than the "quite close to being indestructible" MRF77.

Also, I am certain that if he had chosen a modern radial tyre with a high profile to compare eg. A 235/85r16, instead of a 14ply bias ply tyre, it would have been a clear win for the tall and narrow in contact patch and we wouldn't be having this argument.
I think I might do my own contact patch tests for comparison. Can you even buy bias ply tyres anymore? Wonder when this article was written.

[Disco Muppet]

On modern land rover alloys, as low as 10 to 12psi is quite safe ;)
That's if you're actually going 'off road' as opposed to merely touring.

Sent from my HTC One using AULRO mobile app

[Slunnie]

A 235/85 will bag the same as a 265/75, have the same length contact patch assuming a comparable carcass, but will have a narrower contact patch, but do your testing. :D

[Slunnie]

On modern land rover alloys, as low as 10 to 12psi is quite safe ;)
That's if you're actually going 'off road' as opposed to merely touring.

Sent from my HTC One using AULRO mobile app

Yep, I've spent a week at 10.5psi on sand without any problems. Great bead retainers... unless you're trying to change a tyre!

[Disco Muppet]

And Slunnie and I have personally seen the destruction skinny tyres on army land rovers can do to tracks.

But don't take our word for it, ask people like LowRanger, Brendanm, GoldLeafClover,Chook73, etc who run trucks that take on some of the more extreme tracks, as well as long distance touring, who ALL run wider tyres.
Or are you calling some of the more well respected members of this forum track destroying poser *******? Ironically, Slunnie is also one of the people who I'd put on that list, but you don't seem to want to listen to him :D

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[JoeFriend]

The funny thing is, everyone is arguing but not really answering the posters original questions!!

Any mod you do will have an impact on performance and fuel consumption. In this case, a negative one due to gearing change and more frontal aero resistance.
Do bigger tyres make your car better off road? Yes, and that is about the only thing everyone agrees on. With bigger tyres you will have more diff clearance and better traction. Its up to you how wide you go, which if you go by what everyone says, doesn't seem to matter and is a matter of personal taste.

Military don't mod things so that it is standard which helps repairs and salvaging parts on missions, and if a diff leaks a bit it doesn't matter provided it gets the boys home.

BTW, welcome to the internet - a place that is exactly like the women in my life, always giving me answers for questions I didn't necessarily ask, and conflicting opinions on everything.

Sent from my SM-G900I using AULRO mobile app

[Disco Muppet]

BTW, welcome to the internet - a place that is exactly like the women in my life, always giving me answers for questions I didn't necessarily ask, and conflicting opinions on everything.

:Rolling: :Rolling: :lol2: :lol2:

[DiscoMick]

And Slunnie and I have personally seen the destruction skinny tyres on army land rovers can do to tracks.

But don't take our word for it, ask people like LowRanger, Brendanm, GoldLeafClover,Chook73, etc who run trucks that take on some of the more extreme tracks, as well as long distance touring, who ALL run wider tyres.
Or are you calling some of the more well respected members of this forum track destroying poser *******? Ironically, Slunnie is also one of the people who I'd put on that list, but you don't seem to want to listen to him :D

Sent from my HTC One using AULRO mobile app

You seem to be getting irate about things people DIDN'T say.

Sent from my GT-P5210 using AULRO mobile app

[Disco Muppet]

What am I getting irate about Mick?
I'm enjoying the banter in this discussion, my issue is with comments like this.


On a 4WD, wide tyres are just for looks. On a formula 1 car they are for on road grip.

The best tyres for 4WDing in ALL off road circumstances are tall and narrow


And


..there you have it Paul200, fat tyres are for those who want to get through tracks that those with fat tyres have pointlessly wrecked before them. Awesome.


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[rangieman]

Mmmm realy at the end of the day its horse`s for course`s
I have run both at separate times tall fat swampers And skinny 7.50/16s.
It the late 80`s when 31x10.5/15`s were classed as a big tyre i out drove 2 rangies in mud and ruts driving a s111 swb 4cyl with 7.50/16`s simply because there fat tyres sat on the walls in the ruts.
The 7.50/16s sat on the bottom of the rut :p
So easch to their own :angel:

[loanrangie]

Mmmm realy at the end of the day its horse`s for course`s
I have run both at separate times tall fat swampers And skinny 7.50/16s.
It the late 80`s when 31x10.5/15`s were classed as a big tyre i out drove 2 rangies in mud and ruts driving a s111 swb 4cyl with 7.50/16`s simply because there fat tyres sat on the walls in the ruts.
The 7.50/16s sat on the bottom of the rut :p
So easch to their own :angel:

Exactly, and different terrain requires different tyres
Most tyres we fit on Landy's are not big compared to what the jap 4wders fit so big is relative.

[Jeff]

Exactly, and different terrain requires different tyres
Most tyres we fit on Landy's are not big compared to what the jap 4wders fit so big is relative.

Some on here probably remember when 7.50 was big and 6.00 was normal, let alone 205, 235 etc.

Jeff

:rocket:

[goingbush]

Some on here probably remember when 7.50 was big and 6.00 was normal, let alone 205, 235 etc.

Jeff

:rocket:

Yep. My first series 2 had 7.00 16 road track Majors,

could not wait till I scraped up enough money to go to Olympic factory in Port Melbourne and buy a set of 7.50-16 "Blem" Bar Treads

there awesomeness of those big tyres was amazing, but of course that little 2 1/4 seemed underpowered then, I had to start saving for a Red Motor conversion

and so on it goes :)

[Ancient Mariner]

Double **** here:D 750x16 front 12x16.5 rears 900x13 on the trailer.With 900x13 s on the trailer you could manouver by hand on sand or salt flat but not with 750 x 16s even with a 15 footer snapping at your arse so if any one thinks wider tyres on sand are not better either little 4wd experience trolling or smoking that funny stuff:D For any extensive sand work 900x 13 on about 10 psi allround

AM

[DiscoMick]

Same here. On the farm as a kid we had a WWII Jeep and later a Series Landy, both with big knobbly tyres. Not sure of the exact size, but we ddn't worry about punctures. Mud wasn't a problem, even when scrabbling around on a steep hillside in the bananas.

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[Slunnie]

Double **** here:D 750x16 front 12x16.5 rears 900x13 on the trailer.With 900x13 s on the trailer you could manouver by hand on sand or salt flat but not with 750 x 16s even with a 15 footer snapping at your arse so if any one thinks wider tyres on sand are not better either little 4wd experience trolling or smoking that funny stuff:D For any extensive sand work 900x 13 on about 10 psi allround

AM
Cracker of a setup there, love that vehicle!

[Fluids]

Pros & Cons ... depends on the vehicle the tyres are fitted too as well ...

Years ago I owned a S111 SWB canvas top 2.25L, fitted with Wrangler 7.50 x 16 on std LR rims.
Mate had a IIa SWB hardtop with a 202 conversion and 31x10.5x15 tyres on sunraysia rims.

Using sand driving as 1 specific example. Stockton Beach ... both of us could travel anywhere on Stockton. Beach front, climb the dunes, soft powdery sand, etc ... both vehicles were pretty capable in this terrain.

For ****s & giggles one day we swapped wheels between the vehicles and tried driving stockton ... wasn't going to happen !!

My SIII with the big tyres (which looked the goods now with BIG tyres) didn't have enough guts to properly drive the bigger tyres in the sand (even aired way down). Had to wring it's neck to make progress and the slightest soft slope would severley impeed progress. Worked OK in the bush though.

The IIa fitted with the 7.50 x 16's just dug holes everytime the clutch was released. Due to the 202 having nothing at low rpm, you needed some right foot to make progress, and the narrower tyres just spun and dug holes and kept getting stuck.
Again, it worked OK in the bush.

If I drive my D2 in the dunes, pretty much it leaves a nice clean tyre tread print behind me wherever I drive. The TC is slipping and preventing the tyres from spinning ... A manual vehicle tends to wheel spin more due to the solid drivetrain and chew the loose surface causing the tyres to sink in more rather than float over the top.

So larger tyres have their place ... but the terrain and vehicle (& transmission type) have a large bearing on what works and doesn't also. There's no 1 size fits all.

... my 0.02c :)

[tact]

Too many of the countering comments change too many variables in this thread. For meaningful comparison - gotta focus on one difference.

OP asked about "big". As I wrote before that can mean taller, wider, or both.

Seems all agree taller means more ground clearance and that's nearly always good.

So why not lock that in and focus on "big" that assumes tall. Only one variable, width.

i.e. Discuss the relative merits of:
- tall&narrow (some passionate proponents here saying this is good for ALL situations and wide is for posers)

VS

- tall&wide

Then a measurable and meaningful conversation can be held

Can we agree that 6-8" wide is narrow. (Eg 235/85/16)

Can we agree that 10-12" or more are wide.

[Mick_Marsh]

For ****s & giggles one day we swapped wheels between the vehicles and tried driving stockton ... wasn't going to happen !!

My SIII with the big tyres (which looked the goods now with BIG tyres) didn't have enough guts to properly drive the bigger tyres in the sand (even aired way down). Had to wring it's neck to make progress and the slightest soft slope would severley impeed progress. Worked OK in the bush though.
And to point out, airing down, although improving traction, increases rolling resistance.
You will need more power and fuel to push that tyre along.
Interestingly, some of the energy from that excess fuel you are burning is transformed into heat in the side walls.
While we're talking about rolling resistance, generally wider tyres have greater rolling resistance. That is why putting wider tyres on will increase fuel consumption.
The tyre manufacturers are trying to develop tyres from materials with reduce rolling resistance. That is why you are hearing "Siica Technology" in reference to tyres nowdays.

[goingbush]

if you take width in relation to diameter

The Hankook Dynapro MT 37x12.5R17 ****** tyres on my truck
37" diameter, 10.5" tread width 37/10.5 =3.5


The Toyo M55 235/85R16 tyres on my caravan
31" dia, 8" tread width 31/8=3.8

so the 235/85R16 are looking good !!

Taller / skinny = the bigger number is better as far as this argument is concerned.

Interco TRXUS 37x12.5R17 have merit, but at $655 each ??
37" dia, 9.3 tread width 37/9.3 = 3.9

Perhaps I've just found my next tyre
http://opw.com.au/tyres/interco/trxus-mt-page-3.html


anyone know the diameter and tread width of a 1920's Dodge
lets say 36" diameter 3" wide 36/3 = 12 Whoah! no wonder the old Dodge is king off road ,
would like to see any modern 4x4 try to follow the Dodge, and its only 2WD !!

https://www.youtube.com/watch?v=nq2jY1trxqg

[donh54]

Love the rollover recovery :sly::D:eek:

Sent from my Nexus 7 using AULRO mobile app

[350RRC]

Because you can have narrow tyres with large rolling diameter :cool:

Larger rolling diameter plays a reasonable part in capability regardless of width... :cool:

Yep,

4WD Monthly (as it was known then) did a story about this 10+ years ago.

The contact patch was bigger on skinnier tyres when aired down, without the plough effect.

I've had 31 x 10.5 x 15 on my POS for years, but it is less than ideal, on or off road.

Mega grip on dry tar, aquaplane in the wet.

When I can conquer inertia all will be different..........

cheers, DL

[DiscoMick]

I was looking at a Harley at the weekend which had a really wide donut on the back and a tall skinny tyre on the front. Can't see either being much use off the bitumen though.

[DAMINK]

Wow great thread. I have been in discussions with a couple of mates about exactly this issue.
One mate has a patrol with 2 inch lift and 285/85/16 muddies on it.
Other mate has a prado with 2 inch lift and road tyres quite thin. 225 ish.....
I have a 2 inch lift disco 1 with 235/75/15 AT.
My AT are total crap. Not to mention 15s!!!!
I planned to go 285/85/16 muddies but after reading this thread im not so sure.
Perhaps i should go thinner and not need to put in those over priced guard flares?

[DiscoMick]

Wow great thread. I have been in discussions with a couple of mates about exactly this issue.
One mate has a patrol with 2 inch lift and 285/85/16 muddies on it.
Other mate has a prado with 2 inch lift and road tyres quite thin. 225 ish.....
I have a 2 inch lift disco 1 with 235/75/15 AT.
My AT are total crap. Not to mention 15s!!!!
I planned to go 285/85/16 muddies but after reading this thread im not so sure.
Perhaps i should go thinner and not need to put in those over priced guard flares?

Standard D1 (I had one) is 235/70/16s not 15s. Next size up is usually 245/70/16s. Above that you need a lift and may need to cut the guards, depending on the size.

[DAMINK]

Standard D1 (I had one) is 235/70/16s not 15s.

Thanks mate. Yea i dont know why it has 15s on it. I hate them with a passion.
I already have 2 inches of suspension lift so only need to do the camel cut i think and i should be able to throw some bigger rubber under there.
Real question is how big can i go without the need for flared guards?

[DiscoMick]

Thanks mate. Yea i dont know why it has 15s on it. I hate them with a passion.
I already have 2 inches of suspension lift so only need to do the camel cut i think and i should be able to throw some bigger rubber under there.
Real question is how big can i go without the need for flared guards?

I had 245/75/16 MTRs with a 50mm lift and they rubbed on the steering arms and occasionally banged the wheel arches on big bumps.
I was told the best size was 245/70/16 which shouldn't rub with a 50 mm lift.
BTW the MTRs in that size were noisy and made the D1 use more fuel and accelerate slower. They also dug big holes in sand (back to the thread topic).

[Tombie]

Standard D1 (I had one) is 235/70/16s not 15s. Next size up is usually 245/70/16s. Above that you need a lift and may need to cut the guards, depending on the size.


People need to stop making that comment without the extra data...

A LIFT doesn't allow bigger tyres... It ONLY changes the static height.

Relocating the arc down (lowered bump stops etc) can allow bigger tyres.

On a D1 a Camel cut will allow 235-85-16 with no issues.

A good set of tyres in that size will give better diff clearance than the patrol mentioned.

[Tombie]

I had 245/75/16 MTRs with a 50mm lift and they rubbed on the steering arms and occasionally banged the wheel arches on big bumps.
I was told the best size was 245/70/16 which shouldn't rub with a 50 mm lift.
BTW the MTRs in that size were noisy and made the D1 use more fuel and accelerate slower. They also dug big holes in sand (back to the thread topic).


Bigger camel cut, and a 1/2 turn on the steering stops would have sorted all your issues.

A LIFT won't.... Unless is so firm that you actually lose benefit.

[DiscoMick]

I did adjust the stops. I didn't want to reduce the vehicle's value by cutting it.

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[Disco-tastic]

On a D1 a Camel cut will allow 235-85-16 with no issues.

Bigger camel cut, and a 1/2 turn on the steering stops would have sorted all your issues.

I had a D1 with 235/86/R16 maxxis bighorns (with camel cut) and they rubbed on the radius arms. from memory the left was worse than the right. I didnt adjust the steering stops though.

I also had a 50mm suspension lift. I was out one day with a land rover training group and the instructor took us to a rock step, told us how to drive up it and then proceeded to have 3 attempts to try and get up, the last of which saw them hit the step on am angle and end up cross axled and wheelspinning because the front bar wouldnt clear the step (defender with standard tyres and height). I went next and pointed the disco at the step, brushed the bar on the rock and walked up it - the instructor thought I had diff locks!

I had bigger tyres because I wanted to tackle bigger obstacles. It did affect gearing and it did wallow a little more around corners. It was also harder to get going on hills and soft sand, though this was more to do with the gearing rather than the tyre type. If I bought another D1 (or D2) id do exactly the same as the extra capability, whether touring or out for fun, was worth the drawbacks (well it was for me, anyway).

I do have one question - what happened to Paul? He hasnt been here since page 1. I wonder if he got the answer he was after :rolleyes:

[DAMINK]

@Disco-tastic thankyou for that reply.
It answered my question.
Im in the market to buy some new rubber in the next week or so and that is what i will aim for. 235/86/R16 maxxis bighorns sound like the rubber im after.
Sorry if im hijacking a thread although it is sort of on topic.......

[goingbush]

Fellas, you might find this interesting , its yank so it will immediately put off most of you but as not apliccable, but actually worth the read if only on how they did the testing.

Massive Mud Tire Shootout: Intro - Four Wheeler Magazine (http://www.fourwheeler.com/how-to/wheels-tires/129-1104-massive-mud-tire-shootout-intro/)

as it happens the tyre that wins is the Hankook that I'm running ;)

Mud Tire Shootout First Place: Hankook Dynapro MT (http://www.fourwheeler.com/how-to/wheels-tires/129-1104-mud-tire-shootout-first-place-hankook-dynapro-mt/)

[DiscoMick]

Very interesting. Hankooks don't get much cred. down here, but seem to be a lot more popular overseas. Good pricing too.

[Vern]

@Disco-tastic thankyou for that reply.
It answered my question.
Im in the market to buy some new rubber in the next week or so and that is what i will aim for. 235/86/R16 maxxis bighorns sound like the rubber im after.
Sorry if im hijacking a thread although it is sort of on topic.......
If you haven't already purchased tyres and want to see what they look like, I have a disco here with 235/85 on it, and a spare set of 4 wheels with them on it if you want to try for size. I'm only 10 min up the road:)

[navman]

IMHO it is a bit of a zero sum game.
So you're on this track and see a nice mud puddle up ahead, so you gun through it. Feel top of the world.
Then someone comes along with tyres 1 inch bigger than yours and guns through. So you come along and guess what? You get stuck in the middle of the bog!
So then you HAVE TO get larger tyres so that you can again gun through the bog, ignoring the fact there is a bypass road around the bog.
AND SO ON.

Larger diameter tyres have a better angle of attack on rock steps and can be aired down more without losing ground clearance, BUT unless this is all you do with your car there are lots of downsides.

Your gearing on the highway is now way out, so no problem fit low ratio diffs.
You now are breaking axles regularly. No problem fit HD axles.
You now break CV joints regularly. No problem etc.
In the search for ever larger tyres , you now need a 4 inch lift and body lift. No problem just spend some more money.
You now have big tyres on at low pressures and you bend all your steering rods and break the tie rod ends. No problem etc . the power steering can no longer cope so you fit a full hydraulic ram steering. No problem etc.

You now have a $10K car that you have "invested" $50K into and it is still worth $10K or less and drives like a pig on anything but gnarly trails.
Regards Philip A



100% agree

[Mercguy]

I've just purchased a set of 235/85/16 KM2's on a nice set of wheels and have no issues with the modifications required to fit them to the RRC. I hardly call that a 'big tyre' mod, but it still requires a decent amount of work to make them fit.

[QLDMIKE]

I have had 225/75, 245/75 and now 265/70 tyres on my Disco, with no noticeable difference in fuel consumption, but with vast differences in handling and off-road ability. The best tyre was the 245/75R16.


Adding a 2 inch lift to the V8 made no difference in fuel consumption, no surprise there.


Years ago I saw my first Cruiser with massive tyres, on an Outback road. The darn thing looked skittish and couldn't cut into the road below the loose surface. Have no idea what it's tyre pressures were, so lets forget that part of the equation. But, my overladen D1 V8 with 225/75 tyres was great to drive.


Noting that larger tyres in some form make off-road work easier, what have people found to be a good compromise on their vehicles? e.g 265/75R16? What is too big?


Disco 1?
Disco 2?
110/Defender (tin can with wheels)

[Disco Muppet]

Just to re-ignite this debate :)
Two days in a row I've managed to get my in-laws toyota bogged in thick, gloopy mud doing work around the property.
Guess what?
It runs skinny tyres ;)
Tall, skinny mud tyres.
I did manage to extract it today with much backwards and forwards and associated hooha, but yesterday it required a snatch out.
From my D2, with tyres that are more biased towards the wide side of things.
Drove on the same ground, didn't get stuck.
Why?
Because it DIDN'T break the surface, merely floated over the top :cool:
Skinny tyres might be great when there's actually hard ground under the slop, but I could have spun these tyres until I was in China.
Now, I need to go see a tyre man about some 265/75s :D

[MR LR]

Just to re-ignite this debate :)
Two days in a row I've managed to get my in-laws toyota bogged in thick, gloopy mud doing work around the property.
Guess what?
It runs skinny tyres ;)
Tall, skinny mud tyres.
I did manage to extract it today with much backwards and forwards and associated hooha, but yesterday it required a snatch out.
From my D2, with tyres that are more biased towards the wide side of things.
Drove on the same ground, didn't get stuck.
Why?
Because it DIDN'T break the surface, merely floated over the top :cool:
Skinny tyres might be great when there's actually hard ground under the slop, but I could have spun these tyres until I was in China.
Now, I need to go see a tyre man about some 265/75s :D
Very few people have experience driving on (in) proper mud ;) that's what you just observed Mr Muppet :D

[BadCo.]

He is also comparing a Land Rover to a Toyota. So not a fair comparison by any means! ;)

[Disco Muppet]

The old tojo ain't that bad. Goes where its pointed most of the time.


Sent from my HTC One using AULRO mobile app

[Mercguy]

Many years ago I worked in qld govt as a hydrographer and our vehicle was the venerable 75 series ute with a huge custom rear, load modified for about 3.6t.

It ran standard split rims and a/t's. used to go through lots of boggy mud, as you do when flood gauging etc. There was no way you would complete a week long field trip without getting the winch out at least once.

There is definitely an art to driving the standard tyres in waterlogged silt and clay.

land anchors and pto winches aside, that 75 and it's 1HZ diesel got us through some pretty hairy moments. As much as I understand this arguments merits and foundation, I have to say it simply is not what I have personally experienced.
We had an 80 series for water quality sampling work and other less serious stuff, and it also used to come as a secondary vehicle on some of the flood trips. It had much wider 265 tyres fitted, and would get bogged quicker than you could sneeze. It got to the point where all the staff would run for the keys to the 75's if we were going on a flood trip. So it wasn't just me, it was half a dozen other guys who felt the same. the 80 was much better on dry dirt roads than the loaded 75 though.

Bear in mind, these were govt work vehicles, used every day, long trips, high mileage between destinations and often a lot of serious bashing to get to the gauging sites. No easy tracks or bitumen driveways here.
They would be fitted and spec'd up by the local toyota dealer (after purchase) to the specific govt requirements for the work, which included additional standards compliance and DOT modification plates. These were not standard spec vehicles. diff locks, heavy duty suspension, PTO's, racks, extra large sub tanks etc... there was a lot of serious stuff under those tojos. They were expensive, and suffered a hard but short (80,000km) working life before the custom bits & pieces would be transferred to a new chassis.

Still, I bought an RRC. because fundamentally there is one thing that separates them from each other.

Comfort.

And I'd rather be comfortably sitting in mud to the sills, surrounded by elegant appointments, than slumped in an ill-supporting toyota seat with a plasticky rubbery utilitarian interior.

Standard tyres on an RRC are pretty skinny too. I haven't been bogged in mine yet, and it's skinny half-worn 225/75 cooper at's have been places that have frightened big 265 MT shod landcruiser owners... Of course when they seee a guy in a standard RRC fjording a flooded creek, or descending a slippery muddy rocky fire trail, they just HAVE to follow... to prove a point (or something like that) and when they get bogged, stall or slide off a track, I have a quiet chuckle. There is nothing more amusing than having to snatch a landcruiser. I have all the good quips lined up for when they start making excuses.

I think I'll try and sum it up this way... While skinny tyres might be the argument, the vehicle theyre fitted to and the driving style have more to do with the equation than just the tyres themselves.

fwiw, Gwagens run some pretty skinny tyres. I've never ever been bogged in one of those. Had a mate who fitted some skinny 35" simex centipedes to his 300GD and that made the thing even more capable. Truthfully, it was unstoppable, and that is a heavy vehicle - about 3.3tonnes (empty) so perhaps it is more about the vehicles dynamics, than just tyres, or the driver.

I love the look of balloons under the wheel arches, but I'm not convinced there is any real positive that outweighs the negative. We shall see. I have some 235/85 KM2's here to shove under the RRC before xmas. Need to do a few mods to get them under though.

I think the disco, is probably a fair bit lighter and more agile than the landcruiser. One of the first things I noticed about the RRC when I got it was how much more articulation there is in a standard vehicle, than in a landcruiser. That may also go some way into explaining why the landrover products are superior offroad vehicles, regardless of tyre width.

[DiscoMick]

Yeah, I'm skeptical about the wide tyres argument. I suspect it has more to do with appearance than practicality. And its fanned by the push by manufacturers to sell more products.

[Roscodaily]

Last time I went to buy bigger tyres, the dealer said they wouldn't fit larger than standard. It's all coming down to getting sued for fitting 'incorrect size tyres' in the case of an accident! Regulating us for air soon!

[BadCo.]

Just send him the rims next time haha

Sent from my Nexus 4 using AULRO mobile app

[DAMINK]

Yeah, I'm skeptical about the wide tyres argument. I suspect it has more to do with appearance than practicality. And its fanned by the push by manufacturers to sell more products.

Same here.
I recently went and purchased some 33 inch MT.
Took quite a bit of work just to fit them.
The effort i went too and the compromise i have to deal with now is hard to justify.
I too have noticed wide tyres are no better in certain situations.
Wet grassy hills is one that seems to catch me out where thinner tyres keep going.

That said i do enjoy the look of the wider tyres.
And in some situations they throw a ton of mud around which i do enjoy.

Cant help but wonder though.
I have an extended family member who is into 4x4 far more than i.
Gets his car in 4x4 magazines for the work he has done.
He has a tojo with 37 inch Mickies.
Quite a LOT of cash to spend on tyres.
All the kit to suit and he goes anywhere.
I do wonder why he would get such big tyres when he is rather experienced and has the money to throw.

[BadCo.]

Um, diff clearance?

Height is a different argument to width.

Sent from my Nexus 4 using AULRO mobile app

[DAMINK]

Um, diff clearance?

Height is a different argument to width.

Sent from my Nexus 4 using AULRO mobile app

Not sure if that was directed at me or not.

If so i will add a bit more. There as wide as 15 houses!
I understand we all want clearance but with height he got a ton of width.
I imagine given he was paying an absolute fortune for said tyres he could have gone a lot thinner yet they are that wide they make my 33s look like stockies!

Im simply putting it out there.
This thread is about width of tyres and the above i speak of are WIDE!

[BadCo.]

Not sure if that was directed at me or not.

If so i will add a bit more. There as wide as 15 houses!
I understand we all want clearance but with height he got a ton of width.
I imagine given he was paying an absolute fortune for said tyres he could have gone a lot thinner yet they are that wide they make my 33s look like stockies!

Im simply putting it out there.
This thread is about width of tyres and the above i speak of are WIDE!

Haha fair enough. Although Simex do a 36x10.5 which to me seems like a good Rover size. So he didn't need to go as wide as 15 houses, maybe you will have to give him a bell and pick his brain then report back to us :D

Otherwise he might just be doing it for show to get into magazines?

Sent from my Nexus 4 using AULRO mobile app

[DAMINK]

Haha fair enough. Although Simex do a 36x10.5 which to me seems like a good Rover size. So he didn't need to go as wide as 15 houses, maybe you will have to give him a bell and pick his brain then report back to us :D

Otherwise he might just be doing it for show to get into magazines?

Sent from my Nexus 4 using AULRO mobile app

He runs a tojo mate as i stipulated above.
But yes i agree if width was a bad thing i imagine he would have gone thinner but still a tall wheel for clearance.
He plays in the high country of Victoria when he is out playing.
Its not just about pretty pictures for mags. He does use it.

The mag he is in is Australian 4WD action.
I cant seem to find a pic quickly as the ones i can see are facebook.

[PSI250]

Haha fair enough. Although Simex do a 36x10.5 which to me seems like a good Rover size. So he didn't need to go as wide as 15 houses, maybe you will have to give him a bell and pick his brain then report back to us :D

Otherwise he might just be doing it for show to get into magazines?

Sent from my Nexus 4 using AULRO mobile app

Only 36 Simex is 12.5 wide.
Can get 35x10.5.

I had 36x11 swamper q78s on my Rangie which was a good size, Now 35x11.5 Simex centepedes which work better in the Vic conditions.

[Mercguy]

Only 36 Simex is 12.5 wide.
Can get 35x10.5.

I had 36x11 swamper q78s on my Rangie which was a good size, Now 35x11.5 Simex centepedes which work better in the Vic conditions.

Got a pic of that? I'd be interested to see how they look under the guards.

[blitz]

This is aimed at the original post

My fuel economy is crap no matter what tyres I run so I drive it like I stole it

As I love to play in sand I have taller and wider tyres 275/70/16 as opposed to the original 205/70/16 it came with with the extra height when I air down to 11 psi it sits about the same height as standard at normal pressure.

At 11 psi I don't get bogged at 30 psi I do

As for looks my disco has so many war wounds it looks like a piece of **** so looks don't count in my books

What does count is my taller wider tyres get me to my fishing spots much faster than my original tyres that if the sand was soft couldn't make it

Make what you will of that - **** fuel economy either way, **** looks so that negates the poser argument I drive past skinny tyres clad cars with ease but that may be driver experience I have also driven past fat tyres cars.

I am thinking about bigger tyres both in height and width as there are often times the sand is so soft that I could use a bigger foot print so my next set of tyres are probably going to be the metric equivalent of 35"

[blitz]

I must add when 4wding off of tracks I use the tread lightly ethos of no damage

[goingbush]

Not Landrover , but big tyres.

I have Hankook 37x12.5R17 MT on my truck, these have done 45,000 km , I reckon I'll easily get another 35 out of them, at least half of that on dirt outback roads. The previous Federals lasted 35k.

These have changed my opinion of big tyres, the ground pressure is very low, its by far the most off road capable 4x4 Ive ever owned & they tyres are a hugely contributing factor to that.

Fuel economy suffered drastically running them at 25 psi on sealed roads, 22L/100km instead of 17L/100km at 35psi .

Have only rotated them once & wearing even, have to be happy about that.

https://www.aulro.com/afvb/images/imported/2017/01/923.jpg

[blitz]

Not Landrover , but big tyres.

I have Hankook 37x12.5R17 MT on my truck, these have done 45,000 km , I reckon I'll easily get another 35 out of them, at least half of that on dirt outback roads. The previous Federals lasted 35k.

These have changed my opinion of big tyres, the ground pressure is very low, its by far the most off road capable 4x4 Ive ever owned & they tyres are a hugely contributing factor to that.

Fuel economy suffered drastically running them at 25 psi on sealed roads, 22L/100km instead of 17L/100km at 35psi .

Have only rotated them once & wearing even, have to be happy about that.



https://www.aulro.com/afvb/images/imported/2017/01/923.jpg

That looks suspiciously like the underneath of a Iveco daily 4x4

[goingbush]

That looks suspiciously like the underneath of a Iveco daily 4x4

Your suspicions are correct. However I have ditched the 'sump guard', stabiliser bar & rotated the track rod for more GC so it looks a little different & slightly less busy under there than most.

[blitz]

Not wanting to highjack the post but got a photo? I'm really interested in getting one

[goingbush]

Not wanting to highjack the post but got a photo? I'm really interested in getting one

Don't get me wrong, its probably the most capable 4x4 you will ever drive, (modified or not) roomy , very quiet & comfortable. Capable of sitting way over the speed limit all day too . But they do have serious problems.

No1 Brakes , No2 Transfer case , No3 Iveco Dealers are useless,
- but with $10,000 you can upgrade the Brakes and I can fix the transfer Case , (Iveco don't care. )
plenty photos on my website
Iveco 4x4 55S17W Going Bush (http://www.goingbush.com/iveco.html)

[Tombie]

Your suspicions are correct. However I have ditched the 'sump guard', stabiliser bar & rotated the track rod for more GC so it looks a little different & slightly less busy under there than most.



Why no sump protection?

[goingbush]

Why no sump protection?

The sump is 600mm off the ground, but the 'sump guard' was about 300mm , Turning the track rod around, which was the lowest part at the front effectively raised it by about 100mm putting it in the way of the sump guard mounts, so off it came.

I can't see myself being blind enough running over anything that high but the sump does sit about 50mm below the level of the bottom of the bumper, it could be an issue if I ran into the back of a small car ( with the brakes being what they are)

Putting a cow catcher on the bottom of the bar is on my list of things to do.

[blitz]

Don't get me wrong, its probably the most capable 4x4 you will ever drive, (modified or not) roomy , very quiet & comfortable. Capable of sitting way over the speed limit all day too . But they do have serious problems.

No1 Brakes , No2 Transfer case , No3 Iveco Dealers are useless,
- but with $10,000 you can upgrade the Brakes and I can fix the transfer Case , (Iveco don't care. )
plenty photos on my website
Iveco 4x4 55S17W Going Bush (http://www.goingbush.com/iveco.html)

Yes I have been following several people with them, you included now that I know you write going bush.

I really like constant 4wd, I did read someone considering putting in the landrover LT330 which is certainly strong enough for it and turns it into a constant 4x4.

I have seen the replacement brake upgrades which look good, but I find it amazing that Iveco don't care.

[goingbush]

Yep its true, Iveco don't care, they prefer to pay for recovery and replace $15,000 TC.s under warranty, than implement a simple fix , dosen't have to be a recall , can be done at service and without removing TC. I can do with the TC still in truck in about 4 hours. No wonder they turned over $ 380,000,000 last year but were in the list of 100 Australian companies to make zero taxable income.

BTW they are constant 4WD , with a 68-32 torque split & locking centre diff. 68% torque to rear 32% to front diff during normal driving.

[DeanoH]

Several Oka owners including myself gave serious thought to replacing our ageing vehicles with the Iveco Daily when Iveco in Dandenong bought two prototypes in a couple of years ago.

At first glance they seemed the goods, similar in size and capacity to the Oka but more 'refined'. The hard part was trying to get any sense out of the Iveco sales team but eventually several of us managed to get to actually see the vehicles, a single cab and a dual cab.

Whilst they were comfortable, quiet and mechanically impressive the general impression I got was of an overly computer controlled vehicle of adequate power but from a tiny 3 litre engine with its neck being rung. There were other annoying issues like the inability to effectively transfer fuel from tank to tank due to poor vehicle software and totally unsuitable wheel/tyre options being offered. The gear box/transfer setup seemed very impressive. A shame that production versions ended up with such a poor version of what is probably a very good gearbox/TC design.

Another negative for me was the parabolic springs. Whilst they should provide good suspension in most applications they have no natural dampening when compared to leaf springs and I thought they just wouldn't cut the mustard in fully loaded serious off road driving. I preferred the lower tech very long semi elliptical leaves of the Oka, not as refined but rock solid reliable and easily re configurable if need be.

Ultimately there were too many negatives in it for me and I decided not to go ahead but re furbish the Oka instead. With the inevitable TC failure problems and Iveco's uncaring attitude I reckon I dodged a bullet here.

One Oka owner sold off his immaculate LT Oka and bought an Iveco daily but has just recently on sold the Iveco and replaced it with a NT Oka. Whilst he enjoyed the comfort of the Iveco Daily he preferred the handling and sure footedness of the Oka. The 'sword of Damocles' transfer case hanging over his head was also an issue that led to this decision.


Deano :)

[rammypluge]

I have fitted larger diameter tyres to most vehicles i have owned, including 2wd's and 4wd's. Once the speedo, tripmeter, odometer, and fuel consumption readouts are corrected, whether that be by simple calculation or an adapter or reprogramming, i found that fuel consumption was about the same or better. If the vehicle's engine revs a lot at highway speeds there is a decent chance fuel economy will get better.

Whether you have an auto or manual, during most driving the revs tend to be kept within a certain band, so changing the gearing with different tyres just means that each gear will get used within a slightly different speed range.

There are a lot of misconceptions about the effects of larger diameter and larger width tyres.

A good way to look at it is to compare a typical bicycle and a monster truck. A monster truck has large diameter and wide tyres and they are brilliant off road, whether in mud or sand, whereas a typical bicycle even though it has large diameter tyres is terrible off road, sinking and losing traction. Of course we can all readily acknowledge that small diameter and narrow tyres are the worst, try taking a shopping trolley off road.

[DiscoMick]

I went down the larger tyres route with the D1, but decided the disadvantages outweighed the advantages in most situations. I have decided the Defender's standard 235/85/16s are more than adequate for my needs, as I have no plans to climb cliffs, so do not intend to lift it or go for bigger tyres.
I guess it depends on each person's needs. If I was building a truck to spend most of its time off road I might think differently. I do like the look of a D1 with 245/70/16 MTs, but its noisy and doesn't brake as well on road.

[tact]

Am finding 255/85R16 rubber on stock Boost Alloy rims on my 2013 Defender, with a BAS tune, are pretty much perfect size.