Thinking of ditching my 37"iRoks and getting some 35" Goodyear MTR/K's. Will there be a big power gain? Also what the difference between: 315/70R/17 and 35/12.50/17?

 

315/70/R17 = 34.362" diameter

A tire listed at 35" could actually be smaller (e.g. 34.5"), so you will have to check the manufacturer's specs for the actual diameter.

Going from 37" to 35" would yield a 5.41% increase in mechanical advantage. I'm not 100 percent sure about this, but I suppose it would "feel" like an increase of 9.73BHP assuming 180BHP to the rear wheels.

 

it would be better than that, as in addition to mechanical advantage, you would also be dropping a lot of weight.

 

True ... and probably less rolling resistance.

 

I was thinking the opposite and go yo 37 . But 35 will be better all around driving....hmmmmm

 

The load ratings might be different?

 

Get some Cooper Discover S/T's you will be glad you did!! Plus made in America! My brother has been in the tire biz for 15 years and he raves about these bad boys!

 

Why do you not like the Irocs?

 

I think he meant it was more the size than the acutual iroks. Just guessing....

I am debating the issue with my lift. Just not sure 37 are economical vs the 35s. I need a lot more axle work with 37s

 

I am wanting 37" irocs on my 15" wheels to have for wheeling and keep my 35s for DD. I will have to see how the JK does with my 4.88s and may run the 37's all the time. I just need to get a little more lift and trim. I will be getting a new TF lift soon.