Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-30-08, 11:27 PM   #1
WestCountyRider
Newbie
Thread Starter
 
Join Date: Jul 2008
Location: Sebastopol, CA
Bikes: Specialized Roubaix Expert Triple
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
WestCountyRider is offline   Reply With Quote
Old 07-31-08, 12:17 AM   #2
jsmithepa
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 1,152
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Was it hot in the garage?

Did u leave the garage door open and kids.......
jsmithepa is offline   Reply With Quote
Old 07-31-08, 05:23 AM   #3
CHenry
Senior Member
 
Join Date: Jul 2005
Location: Mid-Atlantic
Bikes: A bunch
Posts: 892
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
CHenry is offline   Reply With Quote
Old 07-31-08, 07:21 AM   #4
ripperj 
Captain-Fred Militia
 
ripperj's Avatar
 
Join Date: Jun 2007
Location: Central Ct
Bikes: Specialized Roubaix Expert 2007,Stumpjumper 2007,Enduro 2006
Posts: 338
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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#
ripperj is offline   Reply With Quote
Old 07-31-08, 07:49 AM   #5
StanSeven
Super Moderator
 
Join Date: Feb 2005
Location: Delaware shore
Bikes: Cervelo C3, Guru Photon, Waterford, Specialized CX
Posts: 11,929
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 112 Post(s)
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.
StanSeven is offline   Reply With Quote
Old 07-31-08, 08:01 AM   #6
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,056
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 226 Post(s)
Quote:
Originally Posted by StanSeven View Post
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
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-31-08, 09:30 AM   #7
JiveTurkey
Low car diet
 
JiveTurkey's Avatar
 
Join Date: Aug 2007
Location: Corvallis, OR, USA
Bikes: 2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.
Posts: 2,407
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
According to Sheldon, the pressure rating on the sidewall is not the be all, end all:
http://sheldonbrown.com/tires.html#width
JiveTurkey is offline   Reply With Quote
Old 07-31-08, 10:26 AM   #8
smd3
Senior Member
 
Join Date: Mar 2008
Bikes:
Posts: 149
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Air will expand .031psi per 1 degree F rise in temp.
smd3 is offline   Reply With Quote
Old 07-31-08, 11:57 AM   #9
Captain Slow
Banana seat
 
Captain Slow's Avatar
 
Join Date: Nov 2007
Bikes:
Posts: 157
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
Captain Slow is offline   Reply With Quote
Old 07-31-08, 01:01 PM   #10
nkuvu
Recumbent tricyclist
 
nkuvu's Avatar
 
Join Date: Jul 2008
Location: Tucson, AZ
Bikes: Greenspeed GT5
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
nkuvu is offline   Reply With Quote
Old 07-31-08, 01:22 PM   #11
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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
Al1943 is offline   Reply With Quote
Old 07-31-08, 03:15 PM   #12
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,606
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
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:




DannoXYZ is offline   Reply With Quote
Old 07-31-08, 03:35 PM   #13
melville
Senior Member
 
melville's Avatar
 
Join Date: Jul 2007
Bikes:
Posts: 486
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Quote:
Originally Posted by smd3 View Post
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.
melville is offline   Reply With Quote
Old 07-31-08, 04:19 PM   #14
WestCountyRider
Newbie
Thread Starter
 
Join Date: Jul 2008
Location: Sebastopol, CA
Bikes: Specialized Roubaix Expert Triple
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks for all the comments. The tire has only about 1,000 miles on it. It was hot last Saturday, my bike computer read 101F 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.
WestCountyRider is offline   Reply With Quote
Old 07-31-08, 04:32 PM   #15
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,056
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 226 Post(s)
Quote:
Originally Posted by JiveTurkey View Post
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
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-31-08, 04:58 PM   #16
nkuvu
Recumbent tricyclist
 
nkuvu's Avatar
 
Join Date: Jul 2008
Location: Tucson, AZ
Bikes: Greenspeed GT5
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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).
nkuvu is offline   Reply With Quote
Old 08-01-08, 01:49 AM   #17
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,606
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Quote:
Originally Posted by melville View Post
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.

Last edited by DannoXYZ; 08-01-08 at 01:56 AM.
DannoXYZ is offline   Reply With Quote
Old 08-01-08, 07:12 AM   #18
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,056
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 226 Post(s)
Quote:
Originally Posted by DannoXYZ View Post
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 (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 (again not the Ideal gas law) is a pressure/volume relationship that doesn't need ideality of the gas either.

Charles 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 to make the Ideal Gas Law. However for most relationships between pressure, volume and temperature the nR values need not be considered.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 08-02-08, 05:24 PM   #19
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,606
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Quote:
Originally Posted by cyccommute View Post
Gay-Lussac's 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.

Last edited by DannoXYZ; 08-02-08 at 05:46 PM.
DannoXYZ is offline   Reply With Quote
Old 08-05-08, 11:25 AM   #20
BarracksSi
Bike ≠ Car ≠ Ped.
 
BarracksSi's Avatar
 
Join Date: Jul 2007
Location: Washington, DC
Bikes: Some bikes. Hell, they're all the same, ain't they?
Posts: 13,858
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
BarracksSi is offline   Reply With Quote
Old 08-05-08, 01:53 PM   #21
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by BarracksSi View Post
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
Al1943 is offline   Reply With Quote
Old 08-05-08, 07:10 PM   #22
BarracksSi
Bike ≠ Car ≠ Ped.
 
BarracksSi's Avatar
 
Join Date: Jul 2007
Location: Washington, DC
Bikes: Some bikes. Hell, they're all the same, ain't they?
Posts: 13,858
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
BarracksSi is offline   Reply With Quote
Old 08-05-08, 08:52 PM   #23
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by BarracksSi View Post
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
Al1943 is offline   Reply With Quote
Old 08-05-08, 08:58 PM   #24
BarracksSi
Bike ≠ Car ≠ Ped.
 
BarracksSi's Avatar
 
Join Date: Jul 2007
Location: Washington, DC
Bikes: Some bikes. Hell, they're all the same, ain't they?
Posts: 13,858
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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
BarracksSi is offline   Reply With Quote
Old 08-05-08, 09:04 PM   #25
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by BarracksSi View Post
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".
Al1943 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 09:06 AM.