tire pressure

[camaroincal]

Hi, I have P245/55R/16's all the way around and am currently running 25 psi for normal use. I only put about 5,000 miles on my car a year as it's only a weekend car. Anyways, the max tire pressure on these tires is 44 psi, now if I inflated them this much I'd feel every single bump the road. My questiong is, is 25 psi too low for everyday driving? What psi does everyone else use? Thanks

[John D.]

Yes, 25psi is too low for everyday use. They will wear unevenly. I would suggest no lower than 35 psi.

[ravenp]

I ran 60psi at the track once by accident ;)

Wouldn't recommend it... if you want max tire useage, go with recommended(likely 35?)

[Devilboy28]

I'm at 36psi all around with the same size rubber. No problems.

[Dominic]

<blockquote>quote:</font><hr>Originally posted by camaroincal:
Hi, I have P245/55R/16's all the way around and am currently running 25 psi for normal use. I only put about 5,000 miles on my car a year as it's only a weekend car. Anyways, the max tire pressure on these tires is 44 psi, now if I inflated them this much I'd feel every single bump the road. My questiong is, is 25 psi too low for everyday driving? What psi does everyone else use? Thanks<hr></blockquote>

The recommended safe pressure is 30psi all around.

I believe 32 front / 30 wear is appropriate for street use.

[mcjoslyn]

Generally speaking, the higher the pressures, the more you will wear the middle of the tires instead of the edges. The lower the pressures, the more you will wear the edges instead of the middle. In addition, an underinflated tire heats up a lot more. An underinflated tire will ride smoothly but feel sluggish, have mushy turn-in and go around corners with high slip angles or just not much grip at all. An overinflated tire will feel harsh on impact and over smaller bumps, and while responding crisply, will lack grip when pushed hard.

The pressure on the sidewall is the maximum pressure that the tire manufacturer recommends. Exceeding that pressure could compromise the tire. What you are looking for is the point where the tire is essentially flat across its tread surface. That will be based on the tire's profile (its aspect ratio or in this case, the "55") and the weight it needs to support.

This is a rule of thumb from Oscar Pereda, an engineer for BFGoodrich. He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:

(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.

Example: 3,000 lb. vehicle weight
3000/100 = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at rear
With unmodified suspension, the result is 30 psi front, 32 psi rear.

I would use this formula as a start and closely monitor tire wear, ride, and gas mileage and go up a couple of pounds at a time until you feel you have the best pressure for your situation. Remember, you should always check the pressure when the tire is totally cold (usually first thing in the morning). Tire pressures change 1 psi for every 10 degrees of ambient temperature change so you should check and adjust pressures throughout the year.

I hope this helps.

[ July 15, 2003: Message edited by: mcjoslyn ]</p>

[r&ksport]

Mike,

The nose of our cars (engine), is heavier than the rear...

Should read:

Example: 3,000 lb. vehicle weight
3000/100 = 30 psi
Add 2 psi all around = 32 psi
Add 2 psi to heavy end = 34 psi at front
With unmodified suspension, the result is 32 psi front, 30 psi rear.

[ July 15, 2003: Message edited by: r&ksport ]</p>

[mcjoslyn]

You know, I think you're right. :eek:

My bad, thanks for the catch. :D

[camaroincal]

Hey thanks for the informative replies. I'm gonna go put some air in my tires soon. When you go to the track though I've heard you want to drop the pressure in the rear tires? How much?