On a really hot summer day, a tire blew out on me as I walked out of the garage. Only thing I can think of was that the extremely hot driveway asphalt caused the air pressure in the tube to increase the tire's limits. No damage to tire., Not realizing what had happened, went back into the garage, changed tubes, pumped up to tire pressure , and when out to driveway, only to blow out another tube! again, no damage to the tire.

I had this problem, I must've blown at least 6 tubes.
I'd be riding and it would sound like a gun shot. Sometimes at the beginning of a ride. Othertimes in the middle of a ride.
But the freakiest thing was having them explode at 2:00AM while the bike was sitting in our back hall.
The only common denominator was the new Specialized S-Works Mondos I had recently installed.
LBS told me no way, those were top of the line and no one had ever had a problem with them, but they agreed to sell me a couple more for cost.
Same problem continued happening - I checked the internet and found that others were having the same problem with these tires, but the shop still said no way.
In the end they gave me a pair of P3Rs and in the 3 years that have passed have never had a problem with exploding tubes.

??

Just looks like the tire failed to me. Couldn't take the pressure. I had a cheap tire (Hutchinson Flash) do that, on a tandem no less...

If you do the math, your hypothesis doesn't work out.

A properly seated tire is not going to blow up from a rise in pressure, just from a hot day.

Assume you pumped the tire to its maximum rated pressure, there is still a wide safety margin built in to that maximum pressure figure, and the tire is going to be potentially subject to much more heat under heavy braking downhill, than the heat of just rolling out of your garage.

And given that a 10 degree farenheit change in temperature changes tire pressure by 1 psi, http://www.tirerack.com/tires/tirete....jsp?techid=73 even if the air temperature in your tire went up 30 degrees it would not cause a properly seated tire to blow.

Odds are you didn't get the tube seated under the rim either time, and that caused your blow outs.

That rule of thumb is for car tires at ~30-psi. At about 100-psi, the rule of thumb would be that 10 degrees F corresponds to a 3-psi change in pressure. It's a ratio thing.

Not that it makes a difference to what you're saying. Although tire blow-off is not uncommon for decenders who brake a lot, especially tandem teams, but the temperatures involved there are a lot higher than hot asphalt.

Yeah, I realize that, and figured someone would point that out, but you're still talking a less than a 10 psi change if the internal temperature of the tire went up 30 degrees coming out of the garage.

Was the tire bead blown off the rim? If not then it wasn't the tire's fault... must have been something to do with the installation, rimstrip, etc.

As is typical in these discussions, you got the order of failure incorrect. The tire casing failed first, causing the tube to "escape" and ultimately fail as well. That rear tire looks pretty well worn...you probably had some worn casing threads in that spot.

The rim damage looks like you ran into something while trying to stop...

Again, the order of failure is incorrect in that statement. You most likely had the tube "pinched" under the bead of the tire and upon inflation it eventually pushed the bead up out of the rim, allowing the tube to "escape containment" and subsequently pop.

Tubes are not "explosive devices". They can't spontaneously explode inside a tire and cause higher pressures than what is in there to begin with. They CAN be punctured either with an object through the tire or by not having a well installed rim tape (exposing holes in the rim for the tube to fail on), but in those cases they won't make a loud "pop" or "bang" since they are contained inside of the "pressure vessel", or tire.

Tube installation error.

This happened in the middle of the night (while sleeping) and startled the hell out of me. 700x28 Gatorskin with less than 200 miles on it failed at the wire bead. Gatorskins are a serious PITA to install so I wonder if my man-handling of the tire wasn't partially to blame.

http://img849.imageshack.us/img849/4221/tire.jpg

I didn't read all the posts - I had this happen one time - and it was clearly my own fault. I simply tried to get too many miles out of the tire.

It happened about 15 years ago - so not sure about brand names - but think the tire was an Avocet. I'm sure the tube was butyl. A later inspection revealed almost all of the tread was gone - so when I rolled past the intersection with a gravel road - apparently a small, sharp stone went through the casing and tube. The casing was frayed where the tube exploded through it.

BTW - this was before the commonality of cell phones - but I was very fortunate to have a co-worker come by and take me back into town(about 6 miles) within 5 minutes.

Maybe I did, I dunno. The tire didn't have that many miles on it, at most 1500. And this was a 305 gram Roubaix, not some PR3 or anything. It could have been worn in a particular spot, however, so your scenario is quite plausible. There was no warning whatsoever, however. I'd think that a casing defect herniating a tube would have been noticeable immediately prior to rupture. It was a bolt from the blue.

Last summer I had a blow out on a front Michelin tube / PR3 that had been mounted on Fulcrum Race 3 wheels for weeks. It was about 20 miles into a ride; 100 PSI when I started, temperature 85 - 90 degrees, flat smooth pavement, at about 21 mph.

It sounded like a gunshot, which wasn't too funny since I was on the MUP in South Chicago - people around me actually ducked to the ground. There was a ragged hole about 4" long by about 1/4 of the circumference of the tube at what I think had been against the side of the tire. The tube was literally shredded, with little flakes of rubber falling out of the tire when I removed them from the rim. The tire was fine.

I really don't think that it was a pinch flat from the tire slowly going down or I would have had a heck of a time keeping that pace before it went. I never could figure out a violent failure like that. I've never one like it before or since, but I think about it to this day when on fast descents.

Do any of the bike gurus have a suggestion as to the cause on that one?

^That sounds like a classic blow out from having the tube under the rim. Blows out loudly and violently with a big hole in the tube, and often no marks on the tire.

Admittedly that the tire was on the bike for 3 weeks makes it a bit unusual, but it could have been that the tube was pinched under the bead, and took a while to work out to the point that the tube expanded outside the tire and blew out.

Standing next to an old college roommate at the gas station while he pumped up his rear tire with the air hose. He pumped too much air and his tire exploded. I couldn't stop laughing for a week. In fact, I still laugh about it.

By the looks of the pic, that tire is REALLY squared off (i.e. worn)...it may have only been ~1500 miles, but that's on the rear of a tandem, right? With the higher weight loading on the rear it's going to wear significantly faster than if it was on a single bike.

You wouldn't necessarily have much, if any, warning with the failure. Once the weakest part goes, it pretty much "tears" away as the tube attempts to "extrude" out the hole...think of it like trying to tear a piece of cloth (tires are basically made of fabric) with your hands; it's really hard to get the tear started, but once it starts it's pretty easy to keep it going.

It looks squared off, but I don't see any exposed threads. Maybe some threads were exposed right at the area that tore apart, however?

I had a similar tire failure and there was no warning at all.

New tire? A lot of people have brake pads that just sneak over the rim and contact the tire... and this eventually causes a casing failure in that spot.