Tire Pressure Questions

Gunter · Gunter's Garage

Eureka, I found a good set of 7's and 8's x 16 with a new set of stock SC tires. They feel good, look good and give a noticeable wider stance. The normal pressure is given as 29 front and 34 rear for SC's. The new tires show a maximum pressure of 44. Because of that, my question is: Does anyone use more than 29/34 when the tires show a higher maximum? I always used 29/34 on my old set and found that the rear 225/50 shows more wear in the center. In fact, the center has a slight concave (1/8") when a straight edge is put across. Is that because of inadequate or too much pressure?

Superman · 05-20-2003, 12:46 PM

I may get some disagreement here, since people sometimes believe that center wear is caused by the tire expanding too much in the center due to overinflation - but I believe center tire wear is due to heat, usually caused by underinflation. Heat is what kills tires, and this happens in the center of the tread. More air reduces flex and heat.

My tires are, right now, at 35 psi each. The lack of difference between front pressures and back pressures helps to reduce low speed understeer. For many street tires, pressures should be a little higher than most folks think. 33 psi is not enough. 37psi is common in street tires at our autocross events.

1fastredsc · 05-20-2003, 01:03 PM

I run my everday driving 44 with 33psi in the front and 37psi at the rear. Tire wear is even and handling is decent on kumho supras (although some idiot with the car before me put a turbo sway bar in the front and left the rear stock so the front usually pushes a bit).

masraum · 05-20-2003, 01:17 PM

My understanding is that you want about 40 psi when hot, so the tires should be set for that when cold.

thabaer · thabaer's Garage

I eliminated excessive center tread wear when I started increasing the rear cold pressure beyond 34, how much depends on the tire and size. The doods that recommended it described it as the center tread scrubbing from lack of pressure to the road.

IROC · IROC's Garage

The "max pressure" rating on a tire really doesn't have anything to do with how much pressure you should use on your particular vehicle. I would stick with the factory recommended pressures and maybe only temper that with what the factory recommended for *the new tire and wheel combo* you're installing if it is different than what was originally recommended for your car.

Mike