Bicycle Mechanics - Tire exploded

When I took my bike off the hook in the garage today I found the rear had exploded. Everything was fine when I rode last Saturday but today the tire had a 4 inch jagged gash in the center of the tread. The tires are Specialized Pro Roubaix. The sidewall reads 120 psi and I had it inflated to about 125. I guess that answers my question about why it blew but it seems odd that it would happen while it's hanging the garage. Glad it didn't happen while I was speeding downhill.

I thought the tires could handle a little over inflation but I'm going to be a lot more careful from now on.

Was it hot in the garage?

Did u leave the garage door open and kids.......

Tires get hot. Your car tire can get hot enough to bake paint off a floor. A blowout of an over-inflated tire ridden on a hot road in hot weather is no surprise, and you are lucky you didn't blow out at speed. You over-filled the tire cold.

The pressure guages on pumps are not accurate enough to guarantee +- 5#, so I doubt the problem was over inflation if in fact the tire was even close to 125#

Your tire didn't blow from heat or overinflation. A tire certainly can withstand 5 additional lbs. While heat does make the air expand, you would need extreme temperatures for that to happen. Also lots of pressure causes the tire bead to come off the rim and the tub blows at that point.

If you had a jagged cut in the middle of the tread, you likely ran over something sharp and the cut weakened the tread. It finally came apart at the cut at a later time.

Your tire didn't blow from heat or overinflation. A tire certainly can withstand 5 additional lbs. While heat does make the air expand, you would need extreme temperatures for that to happen. Also lots of pressure causes the tire bead to come off the rim and the tub blows at that point.

If you had a jagged cut in the middle of the tread, you likely ran over something sharp and the cut weakened the tread. It finally came apart at the cut at a later time.

You are too quick to poopoo the heat and overinflation. It's likely all three. Overinflated tire in a hot garage with a cut tread...probably all the way to the cords. The pressure ratings of tires only hold for new tires under ideal conditions. Use them in the real world at your own peril ;)

According to Sheldon, the pressure rating on the sidewall is not the be all, end all:
http://sheldonbrown.com/tires.html#width

Air will expand .031psi per 1 degree F rise in temp.

I've kept bikes in my company van on days when the inside temp gets so hot that the computer display turns black, and it hurts to touch parts of the bike when I go to get it out. I've never had a tire blow from the heat.

Sidewall pressure number is a recommendation for optimal overall function. I bet you could go to 160lbs or better before the tire would leave the rim. (That'd actually be fun to try. Next time I need to swap tires...)

On that point - If a tire is going to fail from overpressure, most of the time it's going to lose it's grip on the clincher rim, the tube will herniate out, and KER-POW! Even $7.95 Wally World bike tires won't split down the middle unless they've been damaged...

WestCountyRider - I say tire failure. It's most likely that you ran over some glass or steel and cut the tire. Specialized's road tires are super-thin. I bought an Allez Elite in 2005 that came with tires similar to yours... I swapped them out for Vittoria Zaffiro Pros before I ever turned a wheel on pavement. The Specialized skins are serving on my indoor trainer bike, where hopefully, they'll survive the roller drum.

Something I haven't seen mentioned in the thread is the age of the tire. If it was a very old tire, that could be a factor in it as well.

I'm not too surprised. The Specialized tires I've seen were absolute junk. I've seen them self destruct when brand new. I thought they had given up on selling tires.

Al

Using pressure, you'd probably stretch the bead and blow the tyre off the rim before doing any actual damage to the tyre itself. Most likely that pressure is 2x as high as the max-pressure rating on the side of the tyre. Most likely you ran over something that cut the tyre and casing, but not all the way through. It took some time for the tube under pressure to sever the remaining fibres and blow through. Here's one I had from running over a glass shard:

http://i42.photobucket.com/albums/e346/DannoXYZ/Cycling/BlownTyre1.jpg
http://i42.photobucket.com/albums/e346/DannoXYZ/Cycling/BlownTyre2.jpg
http://i42.photobucket.com/albums/e346/DannoXYZ/Cycling/BlownTyre3.jpg
http://i42.photobucket.com/albums/e346/DannoXYZ/Cycling/BlownTyre4.jpg

Air will expand .031psi per 1 degree F rise in temp.

Not quite that low when starting with 125 psi at, say, 60 deg F, but certainly not enough to blow the tire off the rim! Thanks, smd3, for being aware that Boyle's ideal gas law uses the Kelvin scale.

I believe smd3's number is relative to normal atmospheric pressure of ~14.7 psi. Multiply by ~8 to get a reference to a 120 psi bike tire.

If OP has a gash in the tire, he had it when he hung it up, and it was just a delayed reaction to blow it open.

Thanks for all the comments. The tire has only about 1,000 miles on it. It was hot last Saturday, my bike computer read 101°F when I got to the top of my highest climb. In fact, the road surface was so hot the oil on the chip sealed roads was liquifying. :-) Remember that awful crash in the TdF a few years ago, right in front of Lance?

One other thing that I thought might have contributed is that I've noticed small chards of rock embedded in the tire. About a month ago I dug many of them out of the tread, leaving very small holes, maybe a mm or so deep in the tread. One of those could easily have gone through a crucial layer in the tire.

I'll look for some better tires to replace these. I have some Armadillos on my commute bike but it's like dragging an anchor to ride on those. I'd never have them for my recreational bike.

All in all, a good lesson for me to check my tire treads regularly and to watch the inflation. I just feel so lucky it didn't blow on that big downhill. Again, thanks for the comments.

According to Sheldon, the pressure rating on the sidewall is not the be all, end all:
http://sheldonbrown.com/tires.html#width

The pressure rating can be exceeded but that is only for a tire that is whole and has no structural issues. Given that this tire blew out in the center of the tread, it is highly likely it was cut or had some other structural issue before it blew out. Parking the bike in a hot garage with a compromised tire could easily lead to catastrophic failure. I've had tires blow out ...not off the rim but actual rips in the casing... with less pressure and less heat.

1000 miles on the tire may not seem like much but a whole lot can happen is that short distance...particularly on light tires. That weight has to come from somewhere and it's usually the rubber;)

For the record, I wasn't referring to mileage when I was referring to age.

I had a pair of tires I used very infrequently, but they were hanging on a hook in the garage near a window. After several years of lack of use, decided to put them on the bike for a trip. The rubber was cracked and brittle after being in the sun all that time. But the tires had only a few dozen miles on them (so the tread life was great, the sidewalls... not so great).

Not quite that low when starting with 125 psi at, say, 60 deg F, but certainly not enough to blow the tire off the rim! Thanks, smd3, for being aware that Boyle's ideal gas law uses the Kelvin scale.

I believe smd3's number is relative to normal atmospheric pressure of ~14.7 psi. Multiply by ~8 to get a reference to a 120 psi bike tire.You actually have to use kelvins referenced to absolute-zero to determine pressure-changes. Also ideal-gas law is assumes an ideal gas with zero mass and infinitely small particle sizes. No such gas exists and you have to use correction-tables based upon the temp, many of which is off by over 50%.

BTW, that tyre-blowout I posted above occurred after a rain-ride on Jan-1 2007. Temps were about 55F and it blew approximately 45-minutes after I put it away in the garage.

You actually have to use kelvins referenced to absolute-zero to determine pressure-changes. Also ideal-gas law is assumes an ideal gas with zero mass and infinitely small particle sizes. No such gas exists and you have to use correction-tables based upon the temp, many of which is off by over 50%.

BTW, that tyre-blowout I posted above occurred after a rain-ride on Jan-1 2007. Temps were about 55F and it blew approximately 45-minutes after I put it away in the garage.

Gay-Lussac's law (http://en.wikipedia.org/wiki/Gay-Lussac%27s_Law) (not the Ideal gas law) does not have to assume ideality for the gas. This law is based on the relationship between temperature and pressure and is completely independent of the volume or amount of gas present. It also doesn't need to be used in Kelvin since, in it's usual form, the law is used to calculate pressure at two different temperatures using the same scale. The form in which the law is most often used is

P1/T1 = P2/T2

Solve for the variable that you are most interested in to find the final pressure or temperature.

Boyle's law (http://en.wikipedia.org/wiki/Boyle's_law) (again not the Ideal gas law) is a pressure/volume relationship that doesn't need ideality of the gas either.

Charles Law (http://en.wikipedia.org/wiki/Charles%27_law) is a temperature/volume relationship. It's why your pump heats up as you pump up a tire.

These can be combined with each other and Avogadro's law (http://en.wikipedia.org/wiki/Avogadro%27s_law) to make the Ideal Gas Law. However for most relationships between pressure, volume and temperature the nR values need not be considered.
:geek::geek:

Gay-Lussac's law (http://en.wikipedia.org/wiki/Gay-Lussac%27s_Law) (not the Ideal gas law) does not have to assume ideality for the gas. This law is based on the relationship between temperature and pressure and is completely independent of the volume or amount of gas present. It also doesn't need to be used in Kelvin since, in it's usual form, the law is used to calculate pressure at two different temperatures using the same scale. The form in which the law is most often used is

P1/T1 = P2/T2

Solve for the variable that you are most interested in to find the final pressure or temperature.That equation doesn't work unless you start at absolute zero. Try plugging in for a negative temperature -10C or -10F and you'll find that all of a sudden you have negative pressure!!! The scale's starting point is important. Going from 50-degrees to 100-degrees doesn't really result in the pressure doubling. You need to use that equation in kelvins or rankines with a starting point at absolute zero. You also have to use absolute pressures as well, not gauge-pressure.

So to calculate the pressure-change in going from 50-100F, you convert to rankines:

T1 = 50F = 509 rankines
T2 = 100F = 560 rankines
P1 = 125psiG = 139.7psi absolute
P2 = ?

139.7psi/509 rankines = P2/560 rankines
P2 = (139.7psi/509rankines) *560 rankines
P2 = 154.7 psi absolute = 139psi gauge

So 125psi @ 50-degreesF becomes 139psi @ 100-F. :)

Even then this is idealized and not realistic because we have to account for partial-vapour pressures change of the different constituent gases in air with water-vapour (humidity) having a major non-linear contribution. This is why auto racers use dry nitrogen to fill their tyres.

I need to get a pressure gauge to take with me on a ride.

I had a tire blow out, probably a bead seat failure, but it didn't happen until after I brought the bike inside. I pumped the tires up to their usual high pressures (110f/120r) in my 70-ish degree apartment, rode hard in 90-degree weather for about an hour and a half, sprinted (ha!) a lot, used the brakes a lot, then came home. Walked into my building, up to my floor, rolled the bike through my doorway, and BANG! -- my ears were ringing, a neighbor called from the foyer to ask if I was OK, the front tire's bead had popped loose from the rim, and the tube split open about four inches longitudinally (or would it be "circumferentially"?..).

Thinking about it now, my guess is that my weight while riding was enough to keep re-seating the bead (you'd think that it would help seat it better, though... eh, I dunno). Once I got off the bike to carry it, the tire got the chance to unseat itself.

What I think I should do, then, is experiment to see what pressure I should pump the tires to while indoors so that I'd end up with my preferred pressure during the ride. That's where a small dial gauge can come in handy.

I need to get a pressure gauge to take with me on a ride.

I had a tire blow out, probably a bead seat failure, but it didn't happen until after I brought the bike inside. I pumped the tires up to their usual high pressures (110f/120r) in my 70-ish degree apartment, rode hard in 90-degree weather for about an hour and a half, sprinted (ha!) a lot, used the brakes a lot, then came home. Walked into my building, up to my floor, rolled the bike through my doorway, and BANG! -- my ears were ringing, a neighbor called from the foyer to ask if I was OK, the front tire's bead had popped loose from the rim, and the tube split open about four inches longitudinally (or would it be "circumferentially"?..).

Thinking about it now, my guess is that my weight while riding was enough to keep re-seating the bead (you'd think that it would help seat it better, though... eh, I dunno). Once I got off the bike to carry it, the tire got the chance to unseat itself.

What I think I should do, then, is experiment to see what pressure I should pump the tires to while indoors so that I'd end up with my preferred pressure during the ride. That's where a small dial gauge can come in handy.

I like an analytical approach but what I think happened is that there was a small part of the tube pinched between the tire bead and the rim. Or maybe some tire damage while out on the road. Either way you were lucky to get home before it blew. I don't think temperature changes had anything to do with it.

Al

I forget whether it blew before or after I had my first flat on that wheel. So, yeah, it could've been pinched, even though I really tried to make sure the new tube was installed correctly.

Not too long after that, I bought some talcum powder to make tube changes easier.

I forget whether it blew before or after I had my first flat on that wheel. So, yeah, it could've been pinched, even though I really tried to make sure the new tube was installed correctly.

Not too long after that, I bought some talcum powder to make tube changes easier.

I think some people get in too big of a hurry to fix their flats. I've learned to take all of the time necessary to go around the wheel a couple of time checking both sides looking for possible pinches at the tube/rim interface. I need tire levers to get my tires on but I'm super careful to not pinch the tube with a lever. Basically I treat the tube as if it is as fragile as a new born baby.

Al

Oh, I took my time; I was done riding that day and didn't need to do anything else until the next morning. My first tube change was back before I had pubes.. lol

Oh, I took my time; I was done riding that day and didn't need to do anything else until the next morning. My first tube change was back before I had pubes.. lol

That's why I said "some people".

Yeah, true. Just ask my coworkers how much I'm like "some people". :p

I still want to do the pressure-temperature checks, though. If I get all OCD about it, I may keep track of it over a year and see how it compares.

Yeah, true. Just ask my coworkers how much I'm like "some people". :p

I still want to do the pressure-temperature checks, though. If I get all OCD about it, I may keep track of it over a year and see how it compares.

With high pressure/low volume road bike tires you're going to lose a significant amount of pressure just getting the gauge on and off the valve stem. The changes in pressure that you read may be more about how much air you lose with each pressure check.

I know. For the moment, I'd figure that checking once would give me the pressure, then immediately checking again would give me the difference that a pressure check creates (like, the first reading is 125, then the second is 100, so I could expect that the check itself lost 25 psi.. and I'm guessing at those numbers, too).

I have the same Roubaix Pro tires as the OP. My rear tire blew like the OP's yesterday. It was inflated to ~ 100 psi. It had ~ 550 mi on it.

I have had good luck in the past with Specialized Armadillo tires. I am not sure what to buy as a replacement.

Your tire most likely exploded due to a weak tire carcass from either a cut or aged related deterioration.


I had one blow in the garage the other day. Pumped up the tires on a garage sale bike , three days later it spontaneously blew. (aged related deterioration)

The tire was new in August 2009.

OP says his tire has a 4" rip in the center of the tread. Isn't the most likely reason simply a cut tire?

I've had tires blow twice from the heat in my car. Now I always let out some air before putting a bike or wheel in the car. But in both cases the tire just blew off the rim, no tire damage, rode those tires until they wore out. So something wrong with tire. I'd sure change brands. I just put Conti 4000 on the rear of my tandem, black on black with the black chili rubber. I'm impressed with it so far. Not a glass or stone cut yet.

The casing of the tire was cut or damaged probably during a ride.
There is no way a temperature induced rise in pressure blew through the casing.
Blow the tire off the rim, yes (common) blow through undamaged fiber casing, never.
The bead seat will always give before the casing breaks.

Enjoy

The casing of the tire was cut or damaged probably during a ride.
There is no way a temperature induced rise in pressure blew through the casing.
Blow the tire off the rim, yes (common) blow through undamaged fiber casing, never.
The bead seat will always give before the casing breaks.Yes, the majority of blow-outs that don't have tyre-casing damage is due to the tube being pinched and slipping out under the bead. There are certain combinations of loose-tyre/small-rim that can cause the bead to not seat properly; but these are rare.

I used to go down to velodromes at Encino and Dominguez Hills with 200psi tyres in the back (2-3x a week for 6-years). Big window on the hatchback and the wheels sometimes would be too hot to pick up. Not once did I have a blow-out due to the increase in temperature. Also as previously discussed, the actual pressure increase due to temperature rises is minimal and well within the operating range of the tyre.

The LBS warrantied my tire and gave me a new Mondo with FlakJacket. I like it better than the Roubaix ProII that blew.