At 30 cold, a tire should be about 34psi hot. For best results, call a bridgestone tire vendor like stickboy racing or Mize Mobile. Granted the two guys I mentioned primarily deal in race tires, but they should have brand specific info.
Yes if you start out at 30 cold and you come in and they are 38 hot, that is too high of pressure and they will start to slide on you. Granted it will have to be a hot day or you riding the tire pretty hard but it happens. I did it at summit JC it was very cool in the morning and i didn't keep up on them, by the afternoon sessions when i checked them i was around 37 psi and sliding through turn 1 like no ones business. Now i check them every other session just about
Hey Lance, Mize Motors is about 2 miles from my house! I've stopped in to see him, but only ran into his lackies