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heat and tire pressure(4 posts)

heat and tire pressureDonn
Aug 6, 2001 1:12 AM
Entered my first race over the weekend and had a blast despite my blowout. The sidewall of my Specialized S-Works tire is just shot. It was very hot with temps in the 90s. How much will the psi increase due to the heat? I started the race at 120 psi. Could heat expansion have caused my blowout? Should I have inflated to something like 100 psi instead of 120 at the start?
Heat and altitude will change psi in tires...Bruno S
Aug 6, 2001 3:21 PM
Car tires can gain 4-5 psi when they get hot. Thats 15% more pressure. I don't think you can get bike tires as hot as a car but if you inflated them early morning and raced when it was the hottest they could have gained some psi. But I don't think your blowout was caused by heat expansion. Also when you travel to a higher altitude you will gain psi.
I don't necessarily agree...PaulCL
Aug 7, 2001 10:16 AM
..I was an observer at a friends' triathalon a few years ago when several tires blew up in the heat. Apparently, the participants cranked up the PSI to max, then let the bikes sit in the 90 degree heat during the warmup and swimming section. I remember at least two tires popping in the heat while they just sat on the racks. An official laughed that the tires were blowing becuase of the heat. I dunno...just what I heard.
I would imagine that if you inflated the tire to 120 PSI in your air conditioned basement, then took the bike out into 90 degree heat on 120 degree pavement, the PSI could easily go up 15 -20% - enough to blow them off the rim.
I don't necessarily agree...Donn
Aug 7, 2001 11:08 AM
I witnessed the same thing at a race earlier this spring. A bike was laying in the sun and bang! My tire suffered severe sidewall damage. It was not just blown off the rim. It looked like it was hit with shotgun pellets with small holes and frayed thread along one side of the tire. My LBS had no problem replacing the tire with a new one but it was disappointing to have it happen in a race.