Originally posted by Stazi:
The larger the tire diameter the "flatter" it acts as it contacts the road, so he is right in saying the the contact patch is larger on a bigger diameter tire - if you assume that there is the same amount of tire deflection on both tires.


On his comparison (10" vs 24") it would be a notable difference.

However between a 24" & 25" tire the difference is going to be fairly negligable.

75.4" & 78.5" circumference respectively.

Let's take an average of .125 Pi radians or 22.5 degrees of rubber contact. Which would be on the high side.

That would be 4.72" & 4.9" or a 3.6% difference using the high end of the spectrum. A more realistic number would be around the 3% range.

For reference the difference in tread width alone between a 215 and 225 series tire is 4.7% That's not including the difference in diameter on top of that.

Hence my point was that the difference in the tire diameters we were talking about would have no significant effect on the contact patch.
His example had less then 1/2" difference or roughly under 1.5% difference in maximum contact area.


This doesn't even bring up tread pattern. That can have a much greater effect on actual contact area.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.