Thread: Skinny Tyres Vs Fat Tyres

Originally Posted by isuzurover

I agree with that guy that a tall skinny tyre is best on a touring vehicle. Most of his science is OK, however he has one fundamental flaw - his "mechanical locking" theory assumes that more pressure is better... This implies that a heavier 4x4 is more capable (all other things being equal) - but this is not the case...

I also have my doubts about someone who is sponsored by a tyre seller...

Yes I agree with you on both points to a degree. Having spent 2007 and part of 2008 living in the States, the mindset is totally bigger is better when it comes to off-road. But I must admit that I was kinda glad to be driving a F350 going from Minnesota to Tennessee in a blizzard at -35C with 70Km/h winds (gusts of up to 90+Km/h) and ice on the roads!

However, you can't totally write-off more pressure across the tyres surface area being helpful in gaining grip - because there is truth in it, the issue as I see it is if it's more of a positive or a negative in real world driving...and the answer will ultimately depend on terrain being traversed... I guess it comes down to the fact that like tread pattern, there is no one ideal tyre size and width...it all gets back to what works in most situations. Anyway, I'm not claiming to be an expert.

Originally Posted by PAT303

I think it has more to do with not making ruts in fields. Pat

Come on, pull the other one (or change the facts now they don't suit you). Old-school tractors have quite narrow tyres - I agree. However it is almost impossible to find a new tractor with narrow tyres - except when they are needed to fit between rows of crops...

Sure - it is about ground pressure (and traction ) - just like wider 4x4 tyres are about ground pressure (and traction).

Originally Posted by samuelclarke

Yes I agree with you on both points to a degree. Having spent 2007 and part of 2008 living in the States, the mindset is totally bigger is better when it comes to off-road. But I must admit that I was kinda glad to be driving a F350 going from Minnesota to Tennessee in a blizzard at -35C with 70Km/h winds (gusts of up to 90+Km/h) and ice on the roads!

However, you can't totally write-off more pressure across the tyres surface area being helpful in gaining grip - because there is truth in it, the issue as I see it is if it's more of a positive or a negative in real world driving...and the answer will ultimately depend on terrain being traversed... I guess it comes down to the fact that like tread pattern, there is no one ideal tyre size and width...it all gets back to what works in most situations. Anyway, I'm not claiming to be an expert.

I agree with everything. There are lots of variables. Americans are really good at following fads, etc, etc.

Diameter is a really important factor, as is tyre pressure (I run 7 psi in "difficult" offroad conditions). But after those 2, width is an important factor.

Originally Posted by isuzurover

Sure - it is about ground pressure (and traction ) - just like wider 4x4 tyres are about ground pressure (and traction).




I agree with everything. There are lots of variables. Americans are really good at following fads, etc, etc.

Diameter is a really important factor, as is tyre pressure (I run 7 psi in "difficult" offroad conditions). But after those 2, width is an important factor.

That is quite an interesting point. The stucker we get, the more we lower our pressures and get more rubber onto the track. Surely that is telling us something about running tyres with more rubber on the ground. YEs you can lower a skinny tyres pressure and get more rubber, but you can lower the pressures in a fatties and get even more rubber down.

Originally Posted by Slunnie

That is quite an interesting point. The stucker we get, the more we lower our pressures and get more rubber onto the track. Surely that is telling us something about running tyres with more rubber on the ground. YEs you can lower a skinny tyres pressure and get more rubber, but you can lower the pressures in a fatties and get even more rubber down.

That is a VERY good point Slunnie.

And just to prove that I am willing to put my "money" where my mouth is.... In the interests of research:

I have a 109" IIA ute with an asthmatic 2.25.D, shod with 6yo (old and hard), half worn 285/75-16 MTRs, and a rear locker.

So diameter would be the same as new 7.50s or new 235s

If anyone in WA has an equivalently setup vehiicle (coilers included), I am happy to do a comparison/test.

The prob is that some will say that the tyres are all different yadda yadda yadda when the fatties drive better. Even the 235/85 MTR has a more closed tread compared to the 265+ MTR's.

Ok, so for the conditions that I'll be driving in I'll go for the 245 75 R 16 for the D1.

If I can get a 2" lift passed by the director of finance first, I'll go for the 235 85 R 16.

The BFG A/T's have a good rap for both road and off road so I think I'll head that way.