35x12.50R15 Procomp X-Terrains: 34.7 x 12.7 - 64lbs - 18/32nds

36x12.5-15 Bias Ply TSL: 36.3 x 13.5 - 65lbs - 24/32nds

While the two tires almost weigh the same here is what makes your jump to the TSLs a drastic one.

- First off you are moving up from more than one inch in size, you are moving 1.6 inches. You are running close to a 36.5" basically.

- A huge difference in the radial to bias ply construction. Bias Ply tires have a lot more rolling resistance than radials do.

- Tread depth/amount is another biggie. You are starting off with a lot more tread. More tread = more rolling resistance.

- Also tread design is another factor.

- Lastly you are going from a 12.5 to a 13.5 which also increases rolling resistance.

You put all these together and it explains your loss in power.

Now just imagine going from an 31x10.5 Radial, to a 15/38.5 Bias Ply Bogger..... its going to be a HUGE difference. <img src="/forums/images/graemlins/scared.gif" alt="" />