Bias ply tire pressures

[Chevy454]

The rule of thumb used to be pump them up and then lay a short black mark and check it...you want it to be the same shade across the entire pattern (not black on the edges/light in the middle, or vice versa). For our car, depending on the age of the tires, it was anywhere from 42-46 psi.

Now, some guys (especially the FAST cars) are going the extreme opposite direction...I've heard as low as 12 psi in some cars, and have seen them wrinkle the sidewall while yanking the wheels...and "yes" I'm still talking about an F70 Polyglass! But, some guys run in the middle and do quite well, also. Seems to be different for every car...

I will finish with this bit of worthless knowledge...our Camaro went a 1.8x short time @ ~20 psi on it's 11.7x passes, but has also done it at our normal 42 psi setting...you gotta remember, it's a 6" bias tire, and just when you think you have it figured out you launch and it's Cheech & Chong all over again (Up in Smoke!)...

Your best bet is to hope there are some big tire'd cars running during the same program...us street tire'd cars eat the rubber off the track and make the track really really difficult at times.