[NHRABill]

Originally Posted by UFO

The "universal" PSI is the sidewall max, the safest pressure for the tire. Anything less is "under-inflated". When I go to the race track, I am well over 40 psi on my tires, and the placard in the door jamb is 28 psi. If I run the car's "recommended" pressure, I would roll my tires onto the sidewalls with the grip and G forces.

Sorry, I have to disagree the MAX pressure of a tire is not the safest pressure it is called max for a reason. Yes I understand the logic and results of over inflating the tire for daily commuting use I do it myself, but a fully loaded car or truck with overinflated tires or tires set to the Max is dangerous. This is an obvious observation by most anyone with an ounce of common sense.

The reason I mentioned the Mfr. pressure as a safe starting point and not that of the tire is because the car is designed to be safe at those conditions. If you removed your stock tires and rims from your car increased the size or changed the height of your sidewalls then the mfr. recommendations goes out the window and can only be used as a guideline.

if you are into racing then you understand that all tires have different compounds i wouldn't put the Hoosier quicktimes on my truck to tow my car to the racetrack the same as I wouldn't run a set of McCreary's on my wifes Cadillac. The tires compound, diameter, height, width environmental conditions and vehicle you put them on varies so much that there is NO universal Max pressure. I run 10PSI in my truck tires when running on the beach of NC outer banks I need to drop my motorcycle pressure down to 25 to get better traction when it is a 90 degree hot day and I am cursing the back roads of Princeton, NJ along the river having a good time. i used to run 10psi in my supercomp dragster on a average night where I would run 14 psi in my ultra quick 8 vette under the same conditions. When I was commuting I would run Max psi in the daily driver and no more after I tore the tread off of the tire while driving at a high rate of speed spinning me out at 70mph on the Garden state parkway in southbound summer congestion.

The point is know your car and there is no right answer take all factors into consideration for your ride.

I can't imagine worrying about rolling a sidewall when racing. a 40 or even 50 series tire on a scca course would shred on a high HP and heavy weighted car before it rolled even if set to 10 psi.