Thread: Big Tyres: Pros and cons

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.

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

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

Originally Posted by Slunnie

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?

Sent from my HTC One using AULRO mobile app

"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.

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

Sent from my HTC One using AULRO mobile app

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

Thats it!

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

I want performance!