PV=nRT.

V, n and R are constants. That means P (in N/m^2) rises in direct proportion to T (in degrees Kelvin). You make the call.

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Some are born to move the world to live their fantasies...

https://triomultisport.com/
http://www.mjolnircycles.com/

Yep, I've been in transition areas and heard a few tires pop over the years. If you overinflate the night before, the tires warm up, the air expands and they pop.

I always to leave them a bit underinflated and bring my pump with me to the transition area.

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__________________
JP

my twitter feed

if you pump them up high enough to where this "could" happen, you deserve to have them blow. can you pump your tires up to 180 psi? sure. will it benefit you and make you faster? no and it could be worse...it's physics. tires have a recommended psi for a reason. we've joked about marketing a 17mm 300 psi tire just for triathletes because they'd buy it. it would also be the worst riding tire available...especially for long distance (now it probably would kick ass your on a true velodrome)

The heat can weaken the rubber so if it's already damaged it might go. I was standing in the bike check-in line for Kona 1991 on a hot sunny afternoon and my tire let go. Practically everyone else in line started letting the air out of their tires! :-D Upon inspection, I discovered sidewall damage to the tire that probably happened when the bike was boxed up and being thrown on or off the plane. I'm sure glad it happened then and not overnight.

funny you should post this

on the way down to the bay area on Sat. I remembered to let air out since the bikes were on the back out in the hot sun which is usaully SOP

well after the race yesterday, I was pretty much trashed and forgot to follow SOP, rolled back up to moms and later in the afternoon went to load up stuff to head back to Sac and one of my tires had blown out

I always suggest folks buy new tires for their "A" race. Put 'em on a couple of days before, adjust pressure to manufacturer norms the day before, or the morning of if an IM and go for it.

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Tony Verow MD
Durango, CO 81301
Averow@bresnan.net

Exactly; I'd like to add to the tire structural deficiency (rubbed sidewalls, cuts, fraying) as a reason, the all-too-common poorly mounted tire bead and the tire/rim incompatibility causes too.

Lots of folks don't check that the bead is completely seated uder the hook of the rim or that the tube isn't pinched between the rim and the tire bead. Also, if your folding tire goes on your rim with super ease instead of some coaxing with strong hands and/or levers, there's a decent chance your tire isn't the best choice for that rim.

Those I've seen blow in the heat were not a properly mounted, structurally sound tire but usually one of the above. Mfgs. build in some pretty good safety factors where pressure is concerned.

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Mr. Uncaptured External Costs

Fossil carbon is planetary poison.

I've had tires blow up inside my car on hot days. Talk about a good scare!

No Urban Myth. I can link you to the RR of someone this happened to at the Texas Tri. It was 33 degrees and dark on race morning when he pumped up his tires. By the time he got to T1, it was closer to 60 plus the sun was beating down on the tire.

Its not a myth. Over the years I have heard many tires blow in transition. Just two days ago at the Bare Bones Duathlon in Penticton, BC one of my coached athletes had his tire blow. This race is held at 4PM on Saturday thus the weather is quite warm. His bike must have been a little colder in the car during the car ride down to Penticton because about one hour after he racked his bike we heard the tire blow. He had inflated his clincher to 115 psi and the temperature was about 28 degrees celcius. Its not always about overinflation to 200 psi but about how long the tire is exposed to heat.

I'd say if you're leaving your bike overnight to bring a pump with you in the morning to inflate at that time. You're less likely to have any problems if you inflate your tire close to race time. Good luck.

Peter

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Peter Solymosi
The Tri Bike Fit Studio
Vernon, BC

Just another reason to go with tubulars ;-)

Most good tubies are good up to 150-170psi.

far from a myth.
happens all the time for all the obvious reasons.

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

me too - scared the crap outta me!

Question from reading this thread. I've only done 7 tri's. Am I not pumping my tires up enough?! Seems like alot of people are pumping them up pretty high. I go to 110psi. Higher?

T

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Cancer Survivor
http://www.aircrewphotos.com/tyler

I would be an easy experiment to do, inflate to say 100psi, leave in hot car and then take out the wheel and check. I will have to try this one in Arizona.

Only blowout in transition I had was due to the sidewall being damaged. Fortunately it occured when I was taking my bike out of transition after the race.

Kevin

check the sidewall on yours...or check with the mfr.

some Contis, like the GP Supersonic are rated to 170. the Vittoria Rubinos on my new Caliente are rated to 130.

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Train hard...race well.
www.jimmishler.com
"Jim, I happen to agree with you" DougStern

A classic tri moment from the early days when races and transition areas were smaller and the transition was closer to the water, was to have everyone standing in knee deep water with about three orfour minutes before the gun goes off only to hear a loud pop like a gun shot and for everyone to know instantly that someone just blew a tire. Then it was simply a matter of playing the lottery, do the swim and hope that it wasn't your tire. Personally, I never went for the extremely high pressures so I was never too concerned.

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Behold the turtle! He makes progess only when he sticks his neck out. (James Bryant Conant)
GET OFF THE F*%KING WALL!!!!!!! (Doug Stern)
Brevity is the soul of wit. (William Shakespeare)

I had a tire pop on my CompuTrainer this winter. Talk about jacking the 'ol HR up, sounded like a 12g going off in my little apartment

Turns out I'd pinched the tube when I changed tires, so it wasn't heat related, just funny as shit.

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Mike R

Software Engineer and Mac geek
Aspiring to be front-middle-of-the-pack in 2010.

 I leave mine at about 100 until race morning....then pump about 5 psi shy of the max on the sidewall...I ride Vittoria Open Corsas clinchers, they're rated to 130 so I leave 'em at 125. Tubulars can go a bit higher.

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__________________
JP

my twitter feed

The rubber getting hot in the sun wouldn't be a factor in these blowouts, as the rubber really isn't there for structural integrity. It is just there as flexible material to hold the casing threads together and for traction etc. The casing threads are what gives the tire it's strength and are probably made of nylon or polyester like car tires, and are super tough.

As for the tires blowing off in transition, I would bet most of the tires have been mounted with part of the tube pinched under the bead. As the pressure gets higher, it starts lifting that part of the bead until it pushes it over the rim flange and blows. It takes a little extra time, but when you mount a tire, it's best to partially inflate it and then deflate it.Then inspect the bead by pushing the sidewall of the tire away from the rim flange with your thumbs and looking down to make sure the tube is fully inside the tire. Do it all the way around and on both sides. If you see the tube pinched in a spot, lift and roll the tire so it "works" the tube inside the tire so you can't see it. Once it's all clear inflate it and then give it a spin and watch the bead line next to the rim. It's put there so you can tell if the tire is properly seated on the rim. It should be pretty much even all the way around. If the bead line dips down to the rim in a spot, it not seated all the way and you may have to pump it a little higher to seat it and then let a little air out. If the bead line jumps away from the rim in a spot, the tube is probably pinched there and you better deflate it and check it, as that's where it's likely to blow off.

Get in the habit of doing this, it only takes a minute once you practice a few times, and you'll never have a tire blow off.

Greg.

Sorry Tim,

I didn't see your post before I made mine. I pretty much repeated what you said.

Greg.

No, it happened to me after a race 2 years ago. I left my bike in the car after the race and when i came back both had popped.

It bears repeating, really. Folks act like the heat is the primary factor in these "tire" blowouts when most likely the cause is user error. Failure to inspect tires after mounting, failure to inspect tires for wear or damage, or poor tire/rim combination.

If heat were the only factor then you wouldn't expect blowouts to occur in other conditions. Moisture, say from rain, will sometimes allow a poorly mounted tire to unseat from the rim as well, resulting in a blowout.

I think the "myth" here is that the scorching heat from hot pavement or hot car interiors is the reason for these blowouts; I maintain it's the ulimate cause, the other stuff, the proximate causes.

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Mr. Uncaptured External Costs

Fossil carbon is planetary poison.

I had this happen twice recently to my commuter bike, while it sat in the back of my truck at work after riding in the morning. It would be fine riding in, I'd put it in the truck, I'd return to the truck after work and it would have a flat rear tire. After the second one, I took a close look at the rim tape and found one spoke hole that was partially uncovered. The tire pressure would go up and pop! I replaced the rim tape and it hasn't happened since.

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Kendall Frederick

Orange Park, FL