I have seen people at races let some of the air out of their tires after the race. Why do they do this? Is it to put less stress on the tube or what? Thx
I do this. Probably without real reason. I run fairly high pressure in my race tires and after the race they often sit in the sun in the roof rack or in the back of the truck. I don’t know if the sun heats them up to damaging pressures but why find out the hard way.
Tufo tires can hold up to 200 psi but they recommend that you keep 115 psi while stored. Other brands probably have similar recommendations.
During the summer in Phoenix I do this before I put my bike in the truck. If you ever had a tire blow in the back of your SUV after a long ride you would do this all the time after you have the seat shampoo done 
During the summer in Phoenix I do this before I put my bike in the truck. If you ever had a tire blow in the back of your SUV after a long ride you would do this all the time after you have the seat shampoo done
Man this made me laugh really hard.
It’s sort of like picking all of the plants off of your boat when you trailer it, before you transport it to another body of water. It’s a good precaution against accidentally carrying any harmful airborne microorganisms that you may have inadvertently pumped into your tires.
It’s to keep the tires from exploding if left in a hot car (I do this). You see this more at races, since the tires were pumped up extra hard (140-160psi sometimes), and it’s a lot hotter in the back of a car in the afternoon than it was at 7:00am when you pumped them up.
Actually…
As the air sits in your tires it becomes stale. Stale air becomes heavy from the build up of micro bacteri. You let the air out before the bacteria builds up making the air in the tire heavier. Its always best to use fresh air, without the added weight of the bacteria.
It’s to keep the tires from exploding if left in a hot car (I do this). You see this more at races, since the tires were pumped up extra hard (140-160psi sometimes), and it’s a lot hotter in the back of a car in the afternoon than it was at 7:00am when you pumped them up.
Nonsense. Do the math (and use Kelvin).
Also, the air can settle on one side of the tire, thereby unbalancing the wheel when you ride. Very bumpy.
Actually…
As the air sits in your tires it becomes stale. Stale air becomes heavy from the build up of micro bacteri. You let the air out before the bacteria builds up making the air in the tire heavier. Its always best to use fresh air, without the added weight of the bacteria.
That’s why I am so slow!
Assuming: initial pressure of 150psi, outside temp of 95F (308K), temp inside car with windows closed 150F (314K)
Then the pressure in tires would increase to a whopping 1,054,000 Pascal, or 153psi
Correct?
Edit: Assuming that the rubber doesn’t weaken and expand due to the increased heat.
Assuming: initial pressure of 150psi, outside temp of 95F (308K), temp inside car with windows closed 150F (314K)
Then the pressure in tires would increase to a whopping 1,054,000 Pascal, or 153psi
Correct?
Edit: Assuming that the rubber doesn’t weaken and expand due to the increased heat.
150* F is 338 K, so the pressure would be 164, but you get the idea. And the casing is what holds the shape of the tire, not the rubber.
I stand corrected!
In my weak defense - I just finished 90 min on the rollers when I did this.
Checking my notes - I accidentally converted (via google) 105F instead of 150 to K.
Partial credit? 
I do this as well after rides, but only let a little air out. You want the tubes to maintain their stretch a little.
Actually, I got a funny story about this. I had a tire blow while it was sitting in the transisiton area once. It was probably my 2nd or third race ever and it was very hot. I didn’t really know much about bikes at the time and had bought a used pink Bianchi with those big foam padded clip on areobars on it and leather toe clips!
It was a short duathlon, so we were all standing around the start line waiting for the remaining people to get there.(only about 150 in the whole race) We all heard a pop from the transition area and in a couple minutes, a guy comes over and yells out “Anybody got a pink Bianchi?”(nice to have to own up to that one in a big group) So I run over there and really have no clue of how to change my tube, so the guy helps me get the wheel and tire off and we throw the wheel back on and I run back to the start line.
At this point, I’m already pretty gassed from sprinting over to the transition area, learning how to change a tire quick and then bolting back to the start line. My hands are really greasy from not knowing how to correctly put the wheel back onto the chain, I just get back to the start line and the gun goes off for the first 5K run. Man, there’s nothing like starting a race with you HR already at you lactic threshold!
Anyway, it makes for a funny story, but to top it all off, as I get onto my bike after the run, no sooner do I get out of the transition area does my wheel start to slip out of the drops! I didn’t even know enough to make sure that quick release was on there tight enough and some other guy had to help me get it back on there and I was finally on my way.
I now know that brutally steep learning curves are always humbling as they occur, but wonderful life experiences as you look back.
Jeff aka Big Papa Smurf
It’s to keep the tires from exploding if left in a hot car (I do this). You see this more at races, since the tires were pumped up extra hard (140-160psi sometimes), and it’s a lot hotter in the back of a car in the afternoon than it was at 7:00am when you pumped them up.
Nonsense. Do the math (and use Kelvin).
Yeah, might just be tradition, but when I hear all those tires pop in T1 as I walk to the swim…
From the math side (yes, I am an engineer), the pressure would have to increase to twice the pressure on the sidewall (this is typically how they rate a clincher) before the tire blows off the rim; so let’s figure 160psi has to get to 220psi. I agree that’s pretty unlikely (I’m assuming linear pressure increase with increasing temp in deg.K). The variable I can’t account for is the effect of thermal expansion of the rim on the pressure required for the tire bead to unseat, but the inside of a car doesn’t get it nearly as hot as braking on descents. Agreed this myth is busted, but any insights into why we all hear the T1 tire popping Mr. Wizard?
Agreed this myth is busted, but any insights into why we all hear the T1 tire popping Mr. Wizard?
In over 20 years of triathlons, I’ve heard this less than 5 times or so. Maybe I don’t do enough IMs? In any case, I suspect it is due to too many people putting on new tires for the race (why? Beats me) and catching the tube under the bead. Final “top off”, and boom.
I have seen people at races let some of the air out of their tires after the race. Why do they do this? Is it to put less stress on the tube or what?
It restores the natural order to the universe.
I have seen people at races let some of the air out of their tires after the race. Why do they do this? Is it to put less stress on the tube or what?
It restores the natural order to the universe.
Sometimes entropy just needs a little help is all.
Thanks for the hilarious story. Just the image of Big Papa Smurf (presumably light blue with a beard and a big pointy white cycling helmet) on a pink bianchi just makes me LMAO…