instigator

for 235-45-17 & 265-40-17 these are the sizes i am putting on my car and they will be for highway use. can you guys please let me know the pressure that is good for all around driving and good tire wear. thanks

Craig944

I'm assuming the best overall would be what it says along the side of the tire. See how ya like it ;-]

Tom

I notice no difference in factory recommendations for 15" vs 16" wheels and so I would expect the same to hold true for 17" wheels (29 front/36 rear). I have seen Bruce Anderson mention that you don't loose much and get a softer ride lowering the pressures (for street use). I would be wary of that just for rim vs. pothole issues. I find my 944's have handled best with about 5-6 lb more in front than rear. Since the weight distribution is equal, equal pressures would also seem logical. I would start with the factory pressures and work from there just like with the smaller sizes.

Adam Richman

It is my understanding that the 29/36 psi recommendation is done for safety. Basically it creates an understeer condition which at city/highway speeds is safer as most people's reaction to a loss of control is to lift or brake (which would remedy the understeer). I try to run 36/36 on the street (with Kumho Ecstas) and that seems fine for me.

Tabor

My 17" tires have a Max pressure of 45psi. No one wants to deal with that on public streets! Also, it will decrease your skid pad. I run 29/36 like the owners manual says.

instigator

thanks guys. the only reasom i ask is that i had a preconcieved notion that since the tire had less volume( it seemed to ) that it would require either more or less pressure

Tom R.

Without going into the garage, I think the label on my gas cover says 35 f/r for my S2, which has 16's from the factory.

Also, the sidewall pressure is the maximum recommended, not what to drive at. I think the sidewall of the Firestone Wilderness tires says about 35, but the explorer manual says 28.

Maybe you want to try the shoe polish trick the autox's recommend.

adrial

Tom R, that's what my '89 951 says as well. 35 psi f/r. Also with 16" wheels of similar design.

Dave

Craig,
Tom R is correct when he says
A given size tire may fit quite a few different vehicles, each with different pressure requirements. As the manufacturer of the tire doesn't know what you are going to put the tire on, How can they posibly label the tire with the correct pressure?
If you have inflated your tires to the number you found on the sidewall, you are asking for trouble. You need to remember that tire pressure should be measured when the tires are cold. As you drive, friction causes the tires to heat up, and the air in them to expand, raising the pressure. A tire manufacturer takes into account the heat generated at highway speeds, and a safety margin when setting the maximum pressure. Speeds higher than 65-70 MPH (read; drag racing) generate even more heat, which can quickly put you into or even PAST that safety margin.
Please return the extra air in your tires to the wild, where it belongs.
Adjusting the pressure to the levels (or so)recomended by the engineers who designed your suspension, will also drastically improve your contact area, and as Tabor mentioned improve your cars handling.

Dave, 33/35

Perry 951

33 F/R on mine. I have tried any combination from 28-38, 1 tank of gas per psi (most of my miles are highway). Good ride, handeling, and best gas milage (almost 2 mpg better than the 29/32, and 1 mpg less than 29/36)

This was on my stock 16" dials. I will do it again on my 17's soon.

Greg Hammond

I run 225/45ZR-17 fronts, 255/40ZR-17 rears, and I run 32 psi front, 34 psi rear. I've been getting most-excellent traction and very good tire wear on my 951.

Craig - Tire pressures listed on the side of the tire is MAXIMUM permissable pressure. It's never the amount you want to put in the tire for a regular passenger car.

Greg

rpm's S2

I second perry's 33/33 recommendation. My S2 16" factory rims call for 36 but the ride is just too stiff for everyday. I played with everythingfrom 28-36 and found a good compromise. I do not think handling has been affected and mileage has not seemed different. I have been monitoring wear carefully and dso far (4 months) no concerns.