Thread: Tire size and FE with a Jeep View Single Post
CapriRacer
Tire Geek

Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 779
Thanks: 3
Thanked 369 Times in 228 Posts
Quote:
 Originally Posted by stovie I was thinking that a good way to increase ur fe in that jeep is to get class d tires i think they r b/c there able to hit 80 psi and i figured that with lrr tires all they've done is increased tire pressures, i mean think about it this way my jeep is 5300 pounds k 2750 in front 2550 in the back if u take though's and divide them by 2 and then ur tire pressure it gives u square inches that ur tire is on then u divide by tire width and u have inches from front to back and the higher the pressure the less tire contacting the road and less RR.
First, LRR tires are all about the materials used. You can test differing tires of the same size at the same load and inflation pressure and get HUGE differences in RR.

Clearly increasing the inflation pressure does decrease rolling resistance. But what are labeled as LRR tire is connected to the RR when you compare them at the same conditions - meaning size, load, and inflation pressure.

And, no, the formula you've provided is not valid. You can not calculate the area of the footprint just given the load and the inflation pressure. Put another way, the average ground pressure of a tire's footprint is NOT the same as the inflation pressure.

And in case you are thinking that the friction with the road is what RR is all about, that would be incorrect. RR is mostly about the internal friction the material in a tire generate.