I had P265/75/R15 on my 92 F150 4x4 and needed 2 replaced. Then i needed 2 replaced and all they closest to it was 31x10.50 R15. Would that effect the way my truck runs at high speed or at least 65 mph, cause i notice a different feeling from the motor , like it's weaker. By the way i have the 31" up front.
Thanks in advance. Jim

 

Tire height's vary between manufactures,but in general the 265/75 is the same as a 31x10.50.You should run the same size all the way around and from the same manu.

 

The P265/75R15 is a standard load tire, with a similar sidewall to a passenger car tire. They generally have a shallower tread than an LT-designated tire. Even though the overall diameter/height is very close, the difference you feel is likely due to the deeper, more aggresive tread and heavier sidewall of the LT31-10.50R15. Rolling resistance can be considerably greater with the LT tire. Also, if the tread was worn down on the P265/75R15, the new tire with deeper tread will offer higher rolling resistance.