18" Tyres V 19" Tyres

[Disco4SE]

Hi all, I am after some advice. Is there much difference between an 18" tyre and a 19" tyre in the same tyre. Captain obvious tells me that the side wall height is different, but is there much advantage in changing rims from 19" to 18" if the tyre you want comes in a 19" ????????:confused::confused:

[Owl]

Hi Disco4SE
Off road with tyres aired down, you want as much height in the sidewall as possible to enable the tyre to flex over rocks, tree roots etc. Off road, you should be looking for the smallest dia rim and largest dia tyre that is possible / practical.
On road handling you should be looking for the opposite. But how well do you expect a 2-1/2 ton brick with high centre of gravity to handle anyway?!
Ian

[Disco4SE]

Thanks Owl.......does make sense. Seeing as though my off roading is minimal compared to my on road and towing, I am probably better off saving my money on the 18" rims. However, if Gordon can get hold of the GMAX 18" rims, I would still do it.

[Nomad9]

Hi Disco4SE,
The closer you stick to 16 inch rims the better, load carrying capacity, off road ability, availability, cost, all reasons to stick to an 18 rather than go for a 19 inch rim. I was driving back from Canberra to Perth, did a tyre, an 18 inch 255 55 18, could I get one on the way back to Perth, I was stopping at all the major cities and towns, all of them said that they could have one for me tomorrow, a couple were a week due to their location. I ended up sticking another 18 inch 255 60 I think, it was to get me home just in case. Had I had to use this the traction control would have been continually activating, and the gearbox program would change. 19 inch tyres would be even more scarce. One of the recent vehicle tests dropped the Disco 4 from1st place because of the impracticalities of 19 inch tyres. Food for thought............

[sniegy]

Disco4SE,
I remember this discussion a few years ago;)
About the time the D3 was released:p....

I can remmeber when the SE was released & it came standard with 18" rims/tyres (what was LR thinking (back then), how dare they was the outcry) & people questioned/complained that getting tyres was a pain in the preverbial.

Everyone wanted 16's or 17's as this was the "Best" tyre to get.

Nowadays everyone wants 18's as there is a much bigger option than there was 5 yrs ago.

Give it time as in Europe/USA there are again many more options than what we have at present.

As all manufaturers go up in size, the tyre manufacturers will have to keep importing tyres to suit. Supply & demand i think its called.:cool:
Example: The Continentals (ATR) i ordered as it was on the website for 19's, but they are not available as yet in Australia! Available as 18's.
Again more & more tyres are becoming availble in Australia.

Good luck.

I was one of the different ones, My D4 come with 18's & went for the 19's.

Cheers

[trobbo]

massive debate about 17's, 18's & 19's here.

http://www.aulro.com/afvb/general-chat/102515-d4-v-lc200.html

imo there is very little between 18 & 19 particularily if you are trying to get one at short notice. in desperation 18 may be slightly easier to get cause ford territory's have a similiar tyre size.

But as sneigy said the availability will improve as the size becomes more popular. A number of manufacturers are starting to fit 18 - 20 inch rims now.

[rmp]

16-17 is one thing. At 17" there's still quite a bit of space to the rim, although personally I'd rather a 16" rim.

18-19 is quite another. You're really getting low on rim protection by 19", and 18s can't be aired down quite like 17s come to that. Every inch does make a difference when you're out there, heavily loaded in difficult terrain, not so much on a drive day or training course when it's all easy, smooth pre-set obstacles.

Take a 19" tyre out on a High Country trip, air it down to 20psi and watch what happens to your rims as you get onto the hills and cross-axled with the weight on the tyre going from maybe 750kg to 1600kg. See that rim? See the ground? They are virtually one. So, you don't air down as far, and suffer the consequences. However, the D3/D4 is so good it'll still get placed aired up so it looks like there's no disadvantage, but there certainly is. The car's capability is limited, and it's working harder than it would on softer tyres, more wheelspin, more bouncing, more track damage.

You're also more likely to scratch and damage 19s offroad than say 18s as the rim extends that much further into rocks and ruts. Sometimes a recovery is very marginal. Think an off-camber, steep uphill track, rain starting, loose stones, dusk approaching and you need to get the car up the hill. That's when you need every last tiny bit of traction you can muster. I've been there with the six-hour all-night recoveries.

Sand is a different matter as you don't get the weight shift onto single wheels you do in other terrains, and sand doesn't tend to damage rims. The contact patch is the same regardless of profile so flotation is not affected.

Dirt roads are the same deal. When you hit a rock with your tyre you don't want your rim damaged, and the less rubber there is to protect it the greater the chance of damage. Even LR's strong alloy rims can be damaged in this way. Of course you could just avoid rocks but we all make mistakes and if you do enough dirt-road miles it will happen, not if. Perdika track on 19" rims not aired down, anyone? Bad enough on 235/85/16s at 18psi.

I am not convinced there will be a sudden rush of 19" offroad tyres as people in the industry tell me that 20" is likely to be the focus size not 19, as 20s cover a wider range of vehicle and clearly anything running 19 can also run 20. There are quite a number of vehicles with 18" rims but much fewer with standard 19s, but for 20s the number jumps again. However, I do expect some more 19s on to the market even though Goodyear took the 255/55/19 MTR off with the new range. Also, right now there are no tools I've seen to break a 19" bead. There are ways to do it, I've broken a 20" but I couldn't get the damn thing back on the tyre for love nor money, very stiff bead and hard to get into the dropwell. Another story.

Of course, all this it depends what you use your vehicle for. Onroad, a bit of light offroading every now and then on well-made dirt roads and again and 19s will be fine. But that doesn't prove they are just as good as 17s any more than trundling round a racetrack on mud tyres means they're just as good as race tyres just because you completed one lap without killing the tyres through overheating.

The harder and further you go offroad, with a heavier load and the more often, the better the low-profiles become. I'm most willing to be convinced otherwise but so far I don't see any evidence to change my view.

[gghaggis]

The harder and further you go offroad, with a heavier load and the more often, the better the low-profiles become.

Mmmm, methinks a typo in the above ..........



I'm most willing to be convinced otherwise but so far I don't see any evidence to change my view.

Knowing how you feel on this subject, maybe I should only aspire to _partially_ try to convince you :angel:

The way this stands, it's far too open to re-interpretation, mis-direction and general woolly arguments. So let's try to contain it a little.

18" vs 19" current tyres in Australia, on current LR vehicles. That's a start :BigThumb:

So I see 3 general areas here:

1. Issues regarding general availability
2. Issues regarding off-road ability
3. Issues relating to sidewall damage

So ignoring price. And let's assume only legal (max 50mm oversize dia) tyres that fit without modification. Otherwise this becomes a non-ending topic .....

There are only two currently available off-road 19" tyres that fit, so the choice is easy - Goodyear MTR or Pirelli ATR. In 18" there are a select few AT's as well - GG AT2's, GY Silent Armor, Yoko AT/S, but nothing in legal MT's. You're basically stuck with 265/60/18 or 255/55/19

So with regard to point 1:

Out of the cities, if we're restricted to tyres that fit without mods, there is little chance of getting either. Carry your own. The same would apply to std fitment on new Toyo LC's and Prado's.

With regard to point 2:

None of the 18" alternatives will give you the off-road performance of the 19" GY MTR. They are _that_ good. The compromise is road noise. And wear. The Pirelli ATR 19" is as good as any of the 18" in compromise on/off road performance.

With regard to point 3:

Between the 265/60/18 and 255/55/19 there is less than 0.8" in sidewall. This is better than nothing, and in the case of the Pirelli 19" ATR, it _may_ be somewhat significant. As you've indicated, on rocks, shale, you might not want to air down as much (but 25psi will still suffice). On the plus side however a 3.0 ltr D4 on Pirelli ATR's at 25 psi will go further in this kind of terrain than any of the competition. True it's not as good as a mythical D4 on 17" tyres, but it's still better than anything else. In the case of the MTR I don't think it makes any difference worth worrying about.

One could also argue rim damage. If this really concerns you, you probably shouldn't be venturing off-road, as the boys and girls at the golf club will just SCWEAM at what you're doing to your nice new car. Seriously, you'd be going some to really damage it beyond cosmetic issues.

Cheers,

Gordon

[rmp]

Mmmm, methinks a typo in the above ..........

Knowing how you feel on this subject, maybe I should only aspire to _partially_ try to convince you :angel:


Best way to convince me is to advance arguments and evidence. I suspect we'll agree to disagree (again) which is all good with me, I like discussing things with people who hold alternative points of view. It makes me re-examine my own views.



So I see 3 general areas here:

1. Issues regarding general availability
2. Issues regarding off-road ability
3. Issues relating to sidewall damage


My focus has been not on availability, as that's a short-term problem. How short-term it is...anyone's guess. It's not about sidewall damage either as the sidewalls aren't any more vulnerable to damage than a high-profile. It's ability to air down which is a direct effect of #2.




So ignoring price. And let's assume only legal (max 50mm oversize dia) tyres that fit without modification. Otherwise this becomes a non-ending topic .....


Only 15mm in NSW and Vic, but yes.




None of the 18" alternatives will give you the off-road performance of the 19" GY MTR. They are _that_ good. The compromise is road noise. And wear. The Pirelli ATR 19" is as good as any of the 18" in compromise on/off road performance.


This is another point and one I cannot debate as I have no experience of the Pirellis. My point is simple; low-profiles cannot be aired down as far as higher profiles and that restricts offroad capability.





Between the 265/60/18 and 255/55/19 there is less than 0.8" in sidewall.


Doesn't sound a lot, but allow for the flat spot and then put it in percentage terms and 0.8" becomes significant. Like I said, cross-axle a car downhill and see where the rim ends up.




This is better than nothing, and in the case of the Pirelli 19" ATR, it _may_ be somewhat significant. As you've indicated, on rocks, shale, you might not want to air down as much (but 25psi will still suffice).


25psi may well suffice. It very well may not depending on the terrain and I've found 20psi gets you places easier than 25. The difference between say 35 and 30 is far less than the difference between 25 and 25. And 'suffice'...taking a sand dune example you may be able to charge it at say 40psi, make it to the top and say it worked and it would have as indeed the car has arrived on top. Or, air down and do it easier and slower. It's not just can the car get there, it's how comfortably and safely it can do it.

As I said, the Disco is a very capable vehicle so it can certainly go lots of places others need aired-down tyres. The first time I drove a Sport I was astounded at where it'd go on its 20" roadies which I dared not air down. That doesn't mean to say it cannot benefit from airing down further, if it could.



One could also argue rim damage. If this really concerns you, you probably shouldn't be venturing off-road, as the boys and girls at the golf club will just SCWEAM at what you're doing to your nice new car. Seriously, you'd be going some to really damage it beyond cosmetic issues.


For me rim damage is something I'd prefer to avoid, and I prefer to avoid panel scratches. But, it's part of the offroad life. As I don't like either I take steps to minimise both and just put up with what else happens.

However rim damage is not just rock scrapes. It is also bending rims and that's not cosmetic, it's a rim writeoff which is expensive and problematic as then the tyre won't seal and the rim is fatigued and dangerous. Take another rim by all means, but I'd prefer to take steps to avoid the problem in the first place. Alloys cannot be belted back into shape. I'm not advocating steels, but all else being equal, a high-profile tyre does protect its rim better. I don't see how anyone could argue the opposite.

Anyway here's my logic:

1. Given two identical tyres, one high one low profile, which tyre can be aired down further in hilly, rocky, hard terrain?
- high profile, because it protects the rim better.

2. Given two vehicles, identical in every way, one at say 25psi the other at 20. Both have to ascend and descend slippery, muddy tracks. Which one will perform better?
- the aired down vehicle, because contact patch increases (quite a bit) and the tyre is more flexible around stones etc, and it bounces less.

3. If the two identical vehicles above hit identical rocks on a dirt road at 80km/h and both are at any given pressure but one with low and one with high profile tyres which one is most likely to damage a rim?
- low profile

4. Does running lower pressures and speeds lead to less punctures?
- yes, ask any tour operator. Again we come back to the need to run aired down.


I don't think there can be any question about that logic. The last point is particularly pertinent to tourers who maybe don't want to get into really tough forest tracks, but will want to tour on dirt roads.

However that's not really the question now at hand.

The question is; does the D3/D4 need to air down its tyres as far as other cars to keep up with them?
- Answer; no it doesn't, as it's such a superb vehicle offroad.

Therefore, a D3/D4 on low profiles, necessarily aired up more than usual, is still a very good vehicle offroad. But it would be better offroad with high profiles so that's what I run and recommend for others in the same situation. The loss of onroad performance is with highs is far smaller than the loss of offroad with lows.

It's a bit like getting Cathy Freeman to run 200m wearing high heels and because she'll be really quick then saying she doesn't need to wear running shoes.


Is anyone here going to say that, all else being equal, the low-profile tyres perform better in tough low-range going than high-profile tyres? If anyone does believe that I'm genuinely interested to find out why.

[Graeme]

Perdika track on 19" rims not aired down, anyone? Bad enough on 235/85/16s at 18psi.
No thanks!

[discojools]

Just a couple of points re your discussion: With regard to tyre sizes in Vic the rules have changed for offroad vehicles from an increase of 15mm to 50mm for offroad vehicles. Even though I generally agree with you that more sidewall is good for offroad I did meet a D3 owner from Perth who was touring Aus using 19" MTRs. I asked him how they performed offroad and he said that he went everywhere that others went and that he had had only one puncture, a stake through the sidewall and no rim damage.

[rmp]

Just a couple of points re your discussion: With regard to tyre sizes in Vic the rules have changed for offroad vehicles from an increase of 15mm to 50mm for offroad vehicles.

Good news...but please cite the regulations where this is stated. NCOP doesn't count, it's not been adopted by Victoria.

[Bushwanderer]

SNIP
The harder and further you go offroad, with a heavier load and the more often, the better the low-profiles become. SNIP

Hi rmp,
I think that this is the comment to which Gordon was referring. I agree that it is probably a typo and inconsistent with your more recent posts.

Best Wishes,
Peter

[gghaggis]

All eloquently put Robert, and all true. But you can't put 18" tyres on a D4 3.0 ltr, so it's pointless arguing that the car is not as good as it could be. I'm not disagreeing that a mythical D4, with 18" tyres would marginally outperform one on 19's - that's simple physics (but only if it had the 19" car's brake package). I'm arguing that a current D4 3.0 ltr on 19" tyres will out-perform a current D4 2.7 ltr on 18" tyres. Re-reading my last post, maybe that wasn't quite clear:

1. In Sand: As you previously pointed out (and we've done countless times), for sand one can air down a 19" AT to 16psi comfortably. It will climb dunes and wander through soft sand with as much ease as those on 17's and 18's, simply because there is enough longitudinal footprint to apply it's torque advantage easily. And it's not just numbers, but the speed of engine reaction to throttle placement - much better with the 3.0 ltr motor - remember the D3 lag?

2. In rock/shale: About even - the 3.0 ltr driver will need to be more careful with wheel placement, and should limit tyre pressure to 25psi. But he'll have better traction control, better HDC performance, better engine response. I've cross-axled - many times :) - my 3.0 ltr at these pressures. So far no dramas to report!

3. Dirt road touring: I haven't done long-distance touring with 19" tyres yet. Some of my clients have, one with MTR's, and a couple with the Pirelli ATR's. The tyres were never flagged as a weak point (and they did some serious milage on these trips, as you do in WA), but I don't recall what tyre pressures they ran at. The 3.0 ltr however, is again more economical, more responsive and a better tower.

4. Long distance bitumen: 3.0 ltr

I don't think an argument can be made that the 2.7 ltr on 18" tyres is a better package.

On a side note, before people race off to retro-fit 2.7 ltr brake packages. It's not just an argument as to whether the effect on on-road peformance is noticeable. The difference in the two brake systems also influence the traction control performance - it's sensitivity and heat dissipation. One specific issue - I've had the HDC overheat on my D3, whereas the same tracks with the RRS didn't raise any concern. Admittedly the RRS is a little lighter than the D3, but I think the point is still valid.

Cheers,

Gordon

[Disco4SE]

Hi Gordon,
How did you go with the 18"rims that may or may not have fit?

[discojools]

Robert,
Here is the quote from Vicroads Vehicle Standards Bulletin 14 from page 16:

OVERALL DIAMETER
Section LS Tyres, Rims, Suspension & Steering
The overall diameter of any tyre fitted to a passenger car or passenger car derivative must not be more than 15mm larger or 26mm smaller than that of any tyre designated by the vehicle manufacturer for that model.
The overall diameter of any tyre fitted to an off-road passenger vehicle or a commercial vehicle must not be more than 50mm larger or 26mm smaller than that of any tyre designated by the vehicle manufacturer for that model.
Speedometer accuracy must be maintained for the selected tyre and rim combination to within the degree of accuracy specified in ADR 18 where applicable.
The web address is:
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP11_Section_LS_Suspension_and_steering_3Feb2006 .pdf

Hope you can find it.

By the way, have just fitted 245/70/17 BFG MT KM2 to my D3 as an alternative to my 18" Grabber AT2s. These KM2s are hardly noisier than the Grabbers and so far on road I am pretty impressed. Am looking forward to giving them a good test on a Sunset Country trip in a few weeks.. Will report after that.
Strangely the KM2s are not available in 265/70/17, a much more common size for Toyotas and Nissans.

[discojools]

Oh rats,I have just realised that this info is from the NCOP. However my local Tyrepower man told me that Vicroads have change to that recently. I am sure I came across that NCOP Bulletin through the Vicroads website...Here's hoping!!

[rmp]

Oh rats,I have just realised that this info is from the NCOP. However my local Tyrepower man told me that Vicroads have change to that recently. I am sure I came across that NCOP Bulletin through the Vicroads website...Here's hoping!!

Yes, that's NCOP...which is NOT law in Victoria at this time anyway.

With all due respect to your local TP man I've found the big chains to be notoriously poor at knowing what they are talking about. For example, I've just been involved in un-doing fitment of incorrectly load rated tyres to a 4WD which had been recommended by a "professional".

[rmp]

All eloquently put Robert, and all true. But you can't put 18" tyres on a D4 3.0 ltr, so it's pointless arguing that the car is not as good as it could be.


I wasn't arguing that point at all, I was discussing hi vs low profile in general.

The point is relevant for those considering a D4. For really tuff trips I'd go a 2.7 D4 with 17s over a 3.0 with 19s unless it's all sand.





I'm arguing that a current D4 3.0 ltr on 19" tyres will out-perform a current D4 2.7 ltr on 18" tyres. Re-reading my last post, maybe that wasn't quite clear:


Hmmm...I think it would be situation-specific. On sand, yes. On really rocky terrain where the extra 3.0 grunt can't be applied...no. Much of a difference overall...not really. We're not talking about big differences here, it's not like the difference between say a mud terrain and road tyre. Also I would compare 17s to 19s given the 2.7s can work with 17s.





1. In Sand: As you previously pointed out (and we've done countless times), for sand one can air down a 19" AT to 16psi comfortably. It will climb dunes and wander through soft sand with as much ease as those on 17's and 18's, simply because there is enough longitudinal footprint to apply it's torque advantage easily. And it's not just numbers, but the speed of engine reaction to throttle placement - much better with the 3.0 ltr motor - remember the D3 lag?


In sand I agree the extra power of the 3.0 will give it an advantage. The low profiles are less of a problem there. I also would take the 3.0 with 19s over a 2.7 with 18s for a sand drive.





2. In rock/shale: About even - the 3.0 ltr driver will need to be more careful with wheel placement, and should limit tyre pressure to 25psi. But he'll have better traction control, better HDC performance, better engine response. I've cross-axled - many times :) - my 3.0 ltr at these pressures. So far no dramas to report!


Here's where I think a 2.7 with 17s would have an advantage through lower pressures, and the 3.0's extra power isn't the benefit it is in sand. I'm not saying the 3.0 isn't capable, not at all, both vehicles will get there.




3. Dirt road touring: I haven't done long-distance touring with 19" tyres yet. Some of my clients have, one with MTR's, and a couple with the Pirelli ATR's. The tyres were never flagged as a weak point (and they did some serious milage on these trips, as you do in WA), but I don't recall what tyre pressures they ran at. The 3.0 ltr however, is again more economical, more responsive and a better tower.


The 3.0 isn't very much more economical than the 2.7 in cruise mode, but that's nothing to do with the tyres. My concern about 19" tyres with dirt-roading is resistance to rock damage. Mileage for me depends on where you go not how far.





4. Long distance bitumen: 3.0 ltr

I don't think an argument can be made that the 2.7 ltr on 18" tyres is a better package.


Agreed, nobody has made that argument from what I can see. However the 2.7/18 is a VERY good package, even if the 3.0 is better.





On a side note, before people race off to retro-fit 2.7 ltr brake packages. It's not just an argument as to whether the effect on on-road peformance is noticeable. The difference in the two brake systems also influence the traction control performance - it's sensitivity and heat dissipation. One specific issue - I've had the HDC overheat on my D3, whereas the same tracks with the RRS didn't raise any concern. Admittedly the RRS is a little lighter than the D3, but I think the point is still valid.


It is valid, I also made that point elsewhere. The days of easy retrofitting mods are gone with the inter-linked computer age. I never use HDC as I consider it largely a waste of time, probably another argument there I suspect ;-)

[rmp]

Hi rmp,
I think that this is the comment to which Gordon was referring. I agree that it is probably a typo and inconsistent with your more recent posts.

Best Wishes,
Peter

whoops yes that should read high profiles. It's actually inconsistent with ALL my posts early or not ;-)

[discojools]

Robert,
Yes you're right the professionals have no idea.. The bloke who sold me the 245s told me when I first enquired that 5% over standard was allowed in Vic. Also they seem obsessed with putting much higher pressures (40-45psi) in the tyres saying that "Oh yes you'll get much better mileage and mpg out of the tyres". The grip levels are much less especially in the wet as I found out when nearly crashing my old Rangy when I picked it up from service where they had overinflated the tyres.

[rmp]

Robert,
Yes you're right the professionals have no idea.. The bloke who sold me the 245s told me when I first enquired that 5% over standard was allowed in Vic. Also they seem obsessed with putting much higher pressures (40-45psi) in the tyres saying that "Oh yes you'll get much better mileage and mpg out of the tyres". The grip levels are much less especially in the wet as I found out when nearly crashing my old Rangy when I picked it up from service where they had overinflated the tyres.

Where does this 5% rule come from...I have no idea and neither do these tyre 'pros'.

Anyway 40psi for many vehicles is fine (all advanced driving schools I know advocate higer pressures than normal), I run that on my D3. He is correct btw to say mileage is improved and wet-weather grip is also improved. However, go too far on the pressure and grip levels drop and the tyre can be damaged. I once had a tyre shop put 50psi in my Pajero's tyres, just because they could....

[Bushwanderer]

whoops yes that should read high profiles. It's actually inconsistent with ALL my posts early or not ;-)

Hi rmp,
Particularly as you're a mod, ;)do you think that it would be best to edit that post, in order to avoid confusion?

Best Wishes,
Peter