Thread: Wide tyres on a SIII

Originally Posted by isuzurover

What justification do you have for this??? If anything 4x4 tyres would have stiffer sidewalls.

This tyre is at 0 psi. Note the gap between the rim and the rocks.


Many 4x4ers in the US who use military surplus tyres run them at 0 psi offroad.

Sorry, that looks nothing like any of the tyres I have ever run in over fifty years of driving 4x4s when they are at 0psi - and I can assure you I have plenty of experience of the situation. I am quite sure there are tyres that provide substantial support from the tyre structure - what I do question is whether it is likely that the tyres the average Landrover owner runs are likely to fall into that category. Worth noting that tyres where the structure provides significant support should also be expected to generate more heat at road speeds than do ones that do not, and this heat will be reflected in rolling resistance, assuming that the flexing of the structure is not as elastic as is air.

But it certainly points out that ground pressure will depend on the tyre structure as well as the width/diameter. Which brings us back to the original question on width of tyres. I think we would agree that diameter is more important than width, and I would suggest that tyre structure is also important (and less easy to determine).

John

Originally Posted by JDNSW

Sorry, that looks nothing like any of the tyres I have ever run in over fifty years of driving 4x4s when they are at 0psi - and I can assure you I have plenty of experience of the situation. I am quite sure there are tyres that provide substantial support from the tyre structure - what I do question is whether it is likely that the tyres the average Landrover owner runs are likely to fall into that category. Worth noting that tyres where the structure provides significant support should also be expected to generate more heat at road speeds than do ones that do not, and this heat will be reflected in rolling resistance, assuming that the flexing of the structure is not as elastic as is air.

But it certainly points out that ground pressure will depend on the tyre structure as well as the width/diameter. Which brings us back to the original question on width of tyres. I think we would agree that diameter is more important than width, and I would suggest that tyre structure is also important (and less easy to determine).

John

IME the michelins which used to be OEM fitment to Defenders have some of the stiffest sidewalls around. After all, they do have 2 steel belts right through the sidewall!

I would certainly prefer an increase in diameter over an increase in width. However more for the reason that larger diameters roll over obstacles better.

This is still not the article I was thinking of, but getting closer.
The Lowdown, Off Road Tire Pressures | ARB USA Blog

they do not calculate the area of tread in contact with the ground. However, a 7.50 goodyear at 15 psi had a contact patch 27 cm x 15 cm, whereas a wider tyre at the same pressure, had 33 cm x 23.5 cm. So about the same length of contact patch, but significantly wider (due to the wider tread).