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...