Originally posted by supcom
According to my calculations, a tire inflated to 120 psi at normal room temperature of 25 deg C (298 K) will increase to about 130 psi at 50 deg C (323 K). So, if you inflate your tires at, or above the maximum or if your tires are not in good condition, you might consider deflating them slightly.
Supcom has apparently nailed down the science behind this tire popping phenomenon.
It's been a while since I studied chemical engineering, but one equation I remember well was the Ideal Gas Law, which states that PV=nRT, where P=pressure, V=volume, n=number of moles of gas, R=gas constant, and T=Temperature, in degrees Kelvin.
Assuming for a tire that P, V, and R are all basically constant for a tire rated at 120 psi and inflated to that amount, then the equation balances by increases in n offsetting decreases in T... and vice versa.
With that thrilling stuff said, what may be at issue is not so much the absolute temperature, so much as the difference in temperature from when the tire was pumped up to 120 psi vs what it becomes inside a hot car, or in my case, inside a garage. In the situation where I pumped my tire up, I did so in the house, at, say 70F. As the tire's temperature rose more than 50F higher than that, the Pressure inside the tire had to increase beyond the tires rating plus whatever safety factor the good volks at Continental specified. Kaboom.
I suspect that if you leave your bike outside or in the garage all the time, and you're pumping it up to 120 psi when it's 90F outside, the differential in temperature may not be enough to blow the tire.
Now I've used 120psi in my example, but your results may differ. I'd guess this is never a problem for people riding mountain bikes with big gnarly tires that are generally inflated to lower pressures.
One thing I know for sure: I wish I'd seen the thing blow, because the hole was huge and ruined the tire.