While waiting for the start of a group ride tonight the rear tube on my commuting bike exploded and blew part of the tire off the rim and knocked over my bike. I rode 5-6 miles to get to where the ride started and the bike had been standing on the kickstand for about 5 minutes when the tube exploded. A few people were walking by when the tube blew and I thought they threw a fircracker or something at me at first. I put this tube in a week or so ago and had around 50 miles on it before it exploded. I replaced the tube and rode about 15 miles with the group without incident. Has anyone else had anything like this happen? Any ideas as to what could cause it? I couldn't find any problems with the tire or rim.

You had a bit of the tube pinched between the tire and the rim.

Yep ... I had gone for quite a long, cold ride ... brought my bicycle inside, changed, showered, and started making myself something to eat.

About half an hour after I got in ... KABOOM!! Sent me and my cats through the ceiling.

The only thing I can figure was that as the bicycle and tire heated up after being out in the cold, the tire expanded and blew up. But that's just a guess.

Exactly. It happens from time to time.

Had it happen once. 12 miles left on a 50 mile ride. I had stopped for a quick break and was standing about 10 feet from the bike talking to another rider when BOOM. Blew a hole in the sidewall. End of that tire.
Put a new tube in and used a piece of paper to cover the hole in the sidewall. Limped back to my car.

Rather have a blowout that way than while I was on the bike.

Had it happen once when I was at work. My bike was on the other side of the floor, about 20 yards away when it blew. I knew immediately what it was, of course, and didn't flinch, while the rest of the staff freaked out and hid under their desks. Metaphorically, anyway.

Exactly the same thing happened to me when I was a schoolboy oh oh so many years ago. My bike had what we used to call baloontires (read: FAT), and when I should return home from school a cold winter day when the temp was 30 deg C below freezing I had to pump them as they were obviously low on air. Got home and took the bike inside. After a while ... KABOOM!!
Erling.

That's a common guess, but it's not correct. Although the pressure in a tire does increase with a rise in temperature, it does so proportionally to the increase in absolute temperature, usually measured in Kelvin. To convert from celsius to Kelvin, you add about 273.

So, assuming that you were riding at freezing (0 deg C, or 273 K) and brought your bike into 25 deg C (298 K), then the pressure in the tire would increase by a factor of 298/273 = 1.09. If your tire was inflated to 100 psi outside, then it would rise only to 109 psi indoors. This should hardly be enough to blow the tire off the rim! Almost certainly, you had a bit of tube caught between the tire and the rim and it took a long time and a lot of flexing of the tire to allow it to work itself out.

I was riding one day, and all of a sudden my front tire started to feel bumpy. I stopped, looked, and saw a big bulge from the tube starting to poke out. Before I could think, "Yikes, I'd better fix that," it burst.

Fortunately, I was stopped and off my bike. I'm afraid to think what would've happened if it did that while I was going fast down a hill.

Yeah, that is all I could think that could cause it, but it seems really wierd to me that it could happen after 50 miles and a short period of inactivity. I would think it would happen almost immediately while riding.

well, it wasn't really random, but I blew a tube once. It was my friend's bike, and we were like 15. His tire went flat a little ways from home, so we go to the gas station to fill up. We didn't have a pressure guage on us, so he said, just do it by feel since it just has to get him home. Well, I hook it up and turn it on, but neither of us are sure if air is actually going in.

"It still feels squishy. Bend over and listen to see if you can hear air leaking out.", says I. No sooner is his ear right on this thing, the tire blows. I'm not really sure what happened. It didn't feel as if air was even getting in, but there was obviously enough pressure to blow it. Because it wasn't me, and it was his bike, I laughed pretty hartily for about 20 mins, and all the way home.

A LONG, LONG time!! If I'm not mistake that tire and tube combo had about 2-3000 kms on them.

I had one once, had changed the tube, 'thought' that it was clear all the way around, pumped it up and then went to bed. About 30 minutes later, "BOOM". Scared the snot out of me, thought it was a shotgun or something. (fact that the bike is in the hall right outside the bedroom didn't help). I jumped, the cats scattered, mayhem was in full reign.

I suspect that I much have pinched the tube, and it just took it a while to fail. Either that, or the Gnomes are getting more aggressive


Steve W.

it's never random, it's usually a case of, like eveyrone has said, the tube being pinched and slowly working out, or the tire not being seated properly and slowly easing off the rim
one time i was putting the finishing touches on a new wheel, had just installed the tire, had the wheel in the truing stand to pump it up, i had it full (a 27" tire at about 90psi), and decided to check the true of hte wheel one last time, i bend over to check a nipple, and at THAT EXACT MOMENT, the tire popped off the rim right beside my ear and hte tire blew
i fell over and couldn't hear for a few minutes, i was worried that my ear was bleeding
my co-workers nearly killed themselves laughing

I guess the tire gods are mad at me for some reason. I went around 2 years and never had to change a tire on the road. In that time I had one tiny flat from MTBing that didn't appear until I made it home and another slow leak a few blocks from my house that I was able to make it home on. In the past 2 months I have had 6 flats. The one last night, a pinch flat, 3 punctures and a different exploding tube. With the other exploding tube I locked my rear wheel while coming out of a turn at 35mph. The bead seperated from the tire, i ended up cruising on my front wheel and the tube popped. I managed to stay up somehow.

Yeah, but once you've peeled yourself off the light fixture, and have started breathing again ... it's hilarious watching the cats come back around again .... still all fluffed, and hopping like they've got springs in their feet at the least little sound!

I had just gotten home from inflating the tire at the gas station and was setting the bike up in the living room to put the wheel back on when the tube blew. I felt the air presure from ten feet away. Turns out the sidewall had seperated. The thing is that if it had gone off five minutes sooner, it would have been next to me on the passenger seat of my VW Beetle with the windows rolled up. Remember the Bug's reputation for water tightness? Well, they were almost as air tight. I used to have to open the window to shut the door. It most likely would have ruptured my eardrums.

Did the same thing on the first front tube on my Schwinn. Only I pumped it to max pressure, took a 15 mile ride in the morning (mid 70's temp), put it away in the shed... in August... in Texas. Needless to say I had to source a new tube before I rode again.

You don't have a year's supply of tubes, stacked neatly on a shelf, in various sizes to match the tires on your various bicycles at all times???

If I get down to 4 spare tubes in each stack, I'm making a trip or a call to restock the shelf!!




But then my place bears a distinct resemblance to a bicycle shop!

The pinched piece of tube thing is possible, but probably wrong. seeing as how you had ridden it for so long without incident, and the fact that it happened in the cold rather than the warm, i'd say it was your tires that were at fault. you were riding on steel rims, correct? i'd bet money on it. what can sometimes happen in cold temperatures with high pressures (say, 80-85psi) is that the rubber tire will shrink more than the steel rim, which gives a rise in pressure, and boom; your tube blows. i've seen it happen a million times. aluminum shrinks at about the same rate as rubber so you dont have this problem. in fact, it was the Eskimos who first pioneered aluminum rims for that reason.






























that blowout scared the crap out of me

You gotta be kidding... Have you actually measured how much steel, aluminium and rubber changes dimensionally with temperature? Please give the following:

1. amount of temperature change
2. amount of dimensional change of steel rims
3. amount of dimensional change of alloy rims
4. amount of dimensional change of rubber tyres
5. amount of calculated pressure-change
6. actual measured pressure-change

I worked in a shop for over 10-years, and I'd be lucky if I even saw million tyres total the whole time I was there, much less a million blow-outs!

It's just as likely with this statement "...the rear tube on my commuting bike exploded and blew part of the tire off the rim and knocked over my bike." that the tube was pinched between the tyre and rim. The bead is the strongest part of the tyre and the only way to get it off the rim is have the tube wedged between it and the rim. If you overpressurized a tyre enough so that it would blow, there would be a hole in the sidewall somewhere and the bead would still be perfectly intact on the rim .

i'm not surprised you're unfamiliar with this type of blowout, you're from california! a lot of credibility you have then. It'll be obvious to you when you inspect one of these cases. pulling the tire off the rim is near impossible, so it's obvious that that's the problem. i've never experienced that on aluminum rims, but many times on steel.

even though you're not really worth my time, i decided to open up my old physics books just to prove my point:

for a 45 degree fahrenheit drop in temp:
Steel shrinks by .0262%
Aluminum by .07920%
Rubber on bg4533's tires: .07651%

calculated pressure change with aluminum rims: -5.8%
calculated pressure change with steel rims: 29.9%

as you can see, aluminum is quite good and safe. even better are titanium rims, and better still would be einsteinium which provides a pressure change of exactly zero, which was actually invented by albert einstein himself for the purpose of creating bicycle rims. unfortunately the cost of manufacturing the rims was too high, and einstein died before he could see his dream through.

In my case the temperature change would have been from about -10C/14F to about +30C/86F because I had turned the heat up in the apartment when I got in because I was chilled.

And in my case, the bead was still intact on the rim.


Here's the thing ... I worked with all sizes of those foil balloons you find in flower shops etc. that are in different shapes or say "Get Well" or "Happy Birthday" on them for several years.

I would fill the balloons with the same amount of air every single time, and I used to deliver the 10" sized, air-filled, ones at different times of the year.

In the winter the balloons were limp and lifeless when they were in my cold delivery van, and I had some store people panic when I first brought them in ... "These balloons are all flat!!". But give the balloons a few minutes inside where it is warm, and they all plumped up again. We used to have the same problem with the standard latex balloons. Someone would order a whole bunch of them to be placed outside, up and down their driveway or wherever, to advertize a birthday party or something ... in the middle of winter. We would tell them that if they opted to do that, all they would have is a bunch of shrivelled balloons and it would lose the effect. But most people had to see to believe, and we would often get calls asking why we had sold them defective balloons or telling us to come fill them up again. Sorry ... but that's cold air for you!!

In the summer, however, we had to get the air-conditioning going in the van before we put the balloons in there because if we didn't, within about half an hour they would start bursting.

So heat and cold do have an effect on things filled with air!

There was a tear or a weak spot in the sidewall. It happens. It may have been a scrape on something from a long time ago, or a fault in the tire or damage from something else, and finally the sidewall just let the tube escape. And it exploded. It can take a long time or a tear can let the tube out right away.

This is what happened to me. I scraped a rock and did not see any tear in the sidewall when I looked. It was about a 50 mile ride home in the dark. I never really looked at the tire again. I put my bike in the bike stand and fell asleep in the chair about five feet from the bike. The tube escaped and went off like a gunshot about 3:00 am. My kids came down stairs to see if I was shot, and my cat was also in the same room, she still is not the same.

I had the mechanic at the local LBS put new tires and new tubes on a new bike. Rode it later. Both tubes blew, though not at the same time. He had pinched both tubes. How is it possible that a bike mechanic can pinch tubes? I don't know. I don't know.