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Yesterday(16 posts)

Jun 6, 2002 6:27 AM
Yesterday, while cycling home from work, I experienced something new in my more than 85 thousand miles of cycling. Here's the story:

On Tuesday night, I put 100 pounds of pressure in both tires of my beater bike - a ‘spanking new' 1979 Raleigh Super Course. (It's IRC Kevlar belted tires can handle 105 PSI.).

I rode to work without any problem. About 4.5 miles into the ride home – the temperature was in the upper 80s – the bike wasn't ‘behaving' right. At first, it seemed that the chain wasn't securely on the appropriate rear cog. After fiddling with the gear shifter, and finding out that all was well with the placement of the chain, I noticed that the front wheel seemed to be ‘out of true'. To be exact, while the front wheel was in true, the tire was in the process of coming off the rim! I applied the brakes and a few seconds later I heard a loud noise – precisely the noise one hears when one puts too much air into a tube while using a gas station pump. The tube in front had blown.

The tire in question has traveled at least 2000 miles. After a 2.1 mile walk home, I inspected the tire. Examining it while still ‘on' the rim, there didn't seem to be any cuts. Also, there didn't seem to be any weakness on either side of the tire to warrant its coming off the rim.

Has anyone ever experienced a similar thing? Can anyone hazard a guess as to what caused the problem?
...all my troubles seemed so far awayDougSloan
Jun 6, 2002 6:38 AM
I've had tires blow off, but only close to the time they were first mounted. Continental Supersonics on Ksyriums did that to me. I found they just could not hold the rated pressure.

If the tire had been mounted for 2000 miles, and you did not over inflate, that seems odd. Sound like the bead just gave out.

Did the tire appear to be damaged? Hit a big pothole or anything? Maybe the tire was defective, and it just took a while to blow.

Scares the crap out of you, doesn't it?

Now it looks as though they're here to stay.Howard
Jun 6, 2002 7:02 AM
The tire doesn't appear to be damaged. I'll remove it on Sunday and give it a closer look.

The 'scariness index' would have been much higher had I been faster than my 15 MPH speed. I would imagine that if such a thing happened to a cyclist going 30+ MPH - and this tire malfunction led to injury -a lawsuit would be in the making.
Alternate words: Leprosy, All my skin is falling off of me…Tig
Jun 6, 2002 7:28 AM
...I'm not half the man I used to be.

Sorry, but I've had too many friends that love to change song lyrics!
Oh, yesterday came suddenly...DougSloan
Jun 6, 2002 7:38 AM
I don't think I'd use that tire any more. That's too spooky.

Plus, it blows again and hurts you, then you file a lawsuit, someone could make a good argument that you should have known better after it blew once.

So how old are your rims?Spoke Wrench
Jun 6, 2002 6:58 AM
And are they even hook-bead rims?
no beatles tune, sorry.......Jekyll
Jun 6, 2002 7:02 AM
As rims wear from braking the sidewalls weaken. Yours sound like they've been around a while. I would guess that the more material that has been removed through years of braking the more the ability of the rim to hold on to the tire's bead is reduced. Maybe what's going on here.
But Doug is right, usually if your tire is going to to blow off it happens pretty quickly. Nasty either way - glad you had the opportunity to stop before she blew.
then how about some Dylan?Howard
Jun 6, 2002 7:06 AM
One of my wheels is a few years old. The other wheel could very well be, and probably is, circa 1979. Without looking at my bike, which is at home while I'm now at work, I don't know which is which.
post lunchHoward
Jun 6, 2002 9:21 AM
I went home for lunch and checked out the wheel. The front wheel is an original part. It has a Weinmann rim (supposedly a better than average rim for that era). The wheel, and consequently the bike, has slightly more than 15,000 miles on it. (Most of my riding is commutting and running errands mileage and most of this mileage is done with upright handlebar bikes - ATBs and hybrids.)

Q: Can a better than average rim wear out that quickly?
post dinerJekyll
Jun 6, 2002 5:43 PM
feel the braking surface of your rim and see if you can feel a grove in the braking surface (typical wear from braking). If you can feel a grove then your rim may be a little long in the tooth.
Same problem with me wife's beater last weeksurf
Jun 6, 2002 7:13 AM
Same problem with me wife's beater last week
I inflated a cheap performance tire to about 100psi and it blew. After some thought I think it was because the rim just comes straight up, there is no clincher/nipple/curve to the rim for the bead to fit in??? Have any of you come across this??? This is a real beater though, an old Centurion. Take a look at your rim though, it could be the same thing
"I'm not half the man I used to be..."Spoke Wrench
Jun 6, 2002 7:58 AM
Back when I was young and dumb, I routinely overinflated bike tires. I reasoned they HAD to have some kind of safety margin built into their rateings that I could exploit. As I've gotten older, I've become much more conservative about such things. I'm not half as brave as I used to be. There are actually several factors involved.

Bike riders tend to use the terms "wired on," "clincher," and "hook bead" interchangaby. Sutherland's manual says they are three different things that refer to how the tire is held onto the rim. If you plan to use a hook bead tire at it's maximum pressure, you had better be mounting it onto a hook bead rim.

The brakeing surface is an important factor in holding the tire onto the rim. If you inflate a tire to 120psi, you have 120psi trying to push the rim flanges outward. It's easy to see that if the rim flanges flare outward far enough, the tire bead is going to blow off. Old, worn rims gradually lose metal from the braking surfaces and consequently the flanges will gradually flare outward more easily.

Finally there is "erto." Erto stands for European Tire and Rim something or Other. It is an attempt to make sense out of the many tire bead and corresponding rim bead seat diameters. Naturally, tires and rims are typically made by different manufacturers. Both have manufacturing tolerences so it's possible to have a looser than nominal tire to rim fit. Sometimes mounting a cheap tire onto a cheap rim is not a pretty thing. It is sometimes necessary to hold the tire concentrically onto the rim while inflating it. A tire/rim combination that is hard to mount isn't entirely a bad thing because it's more likely to stay put under pressure.
wife's beater? (nm)ColnagoFE
Jun 6, 2002 8:27 AM
did it happen where the valve stem is at?Tig
Jun 6, 2002 7:23 AM
I've seen that a few times when the tube and stem somehow get pushed out of position if the stem's nut gets loose or is off. However, I don't use a nut on valve stems and haven't seen it on my tires.

I wonder how much higher that 100 psi went after rolling on a hot road? I imagine it wouldn't be much, but it could contribute a little, combined with a weakened tire bead.
did it happen where the valve stem is at?Howard
Jun 6, 2002 9:26 AM
Years ago, when obviously the bike and wheel were much younger, I rode that bike in 100 degree temperatures. There never was such a problem.

I don't believe that the tire came off in the valve stem area. In all honesty, however, I didn't think to look there yesterday at the time of the 'event'.
happens to MTB riders all the timeoff roadie
Jun 6, 2002 9:03 AM
Not all RIMS are rated for the same pressures. Mavic is the only company I know that lists the pressures on thier website. Generally, wider rims can't hold as high pressure (psi), because the total force is more (psi x inches of rim area).

The pressure that will push a tire off the rim goes down as the size of the tire goes up- again, theres more area, so you need less pressure if you can only hold so much force. Mountian bikers run into this a lot when they use fat tires and pump the pressure up to high.

Sometimes with big tires, the pressure is low enough that the tire comes off but the tube doesnb't blow. Instead, it bulges out along maybe half the rims circumferance, a phenomina described as "whale dick". I kid you not...