Under hot weather and highway conditions, the temperature of the air inside the tire rises about 50 degrees. That increases the pressure inside the tire about 5 psi. The burst pressure of a tire is about 200 psi.
What is a dangerous psi for tires?
If you have standard passenger tires (ninety percent of vehicles do) the lowest tire pressure you can generally drive with is 20 pounds per square inch (PSI). Anything under 20 PSI is considered a flat tire, and puts you at risk for a potentially devastating blowout.
What psi is too high for tires?
Higher pressure generally is not dangerous, as long as you stay well below the “maximum inflation pressure.” That number is listed on each sidewall, and is much higher than your “recommended tire pressure” of 33 psi, Gary. So, in your case, I'd recommend that you put 35 or 36 psi in the tires and just leave it there.