Street tire pressures....

[99GrandTouring]

Guys What is the lowest you can safely take a street tire down to?
The reason I ask this last time at the track, my rearend would go to the right on launch and 1-2 shift....
I got back to the pits and checked my tire pressure and the drivers rear had 35psi and the passenger rear had only 15psi.. (I didn't check them before leaving home or once I got to the track)

Now with this I did get my best 60ft eventhough the pressure was mismatched....

My questions are.
1. How low can you safely take street tires and how low should you go?

2. Is there anything that could cause a drop in pressure? Just a couple weeks ago they were fine?

3. I drove about 150miles to the track with the tire at this pressure, is that bad?

[Stanman]

What will happen when you run too low a pressure is the carcass of the tire can get hot. In an extreme case this can cause the tread to separate from the cords. That's usually the cause of all the truck tires you see on the freeways. A Z-rated tire is designed to be able to take some heat since it could conceivably run 150+ for hours. So you probably did no damage except excessive tread wear on the outer edges, if you are still running a stock GT wheel tire type combo. If you have 15's and some off brand tires and you start to feel ANY new vibrations your tread is already starting to separate.

to answer #1, I don't know. A z-rated tire has it's max weight rating at about 45 psi yet the car is placarded at 30. This seems too low to me, and I like the way the car responds at 40 psi alot better, tho the ride is harsher. I figure if it's rated at 45 psi I'm uncomfortable under 25.

Your sudden loss is probly a screw or nail. Tho it's possible your valve could go bad or even loosen up inside the stem a sudden loss usually means you picked something up. Or you've been hitting curbs lately!