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dstke 08-12-12 10:16 AM

Blown tubes
We're touring on a tandem with a trailer and have been plagued with blow outs. 3 of 4 occurred when we were heading down from a pass. Two were big blowouts, 8" rip on the tube and blew out the bead on the tire. Two were at the valve stem on heavy duty tubes. All tubes were 700 x 28. The big bow outs were at altitude, 8000' and 6000'. Don't know if it's tire pressure, I pump up the tires with a hand pump every couple days, or if the rim is getting too hot and causing the tubes to blow? In the cases of the two big blow outs we were just starting down the passes and the blow outs occurred in the first 1-2 km. Also we have a drum brake to assist and I had it on both times.
Appreciate any insight or suggestions.

Spoonrobot 08-12-12 01:21 PM

I just did a little reading about this myself.

Tube trapped under the bead? Was there a bang?

Big Lew 08-12-12 01:30 PM

Were you using caliper brakes as well? If so, check closely to make sure they're not coming in contact with the side of the tire. I've had a tire sidewall rip from brake contact. I've also had similar failure from excessive rim heat while using cheap tires.

fietsbob 08-12-12 01:36 PM

I think you have the sequence reversed, the hole in the tire casing let the tube expand out the hole
until it reached its limit of elasticity.. where upon it burst.

2 aboard on a tandem may be better served by a wider tire, IDK.

on my Loaded tour bike I had a tire casing failure , but because I was Running
Thicker Thorn Resistant Tubes, they made an aneurism like bulge out the hole,
but I had time to pull over, let the air out of the tire, then replace the tire,
which I had brought a 3rd one ..

I continued the tour and at the end of several months , i had yet to have a puncture.

Spoonrobot 08-12-12 01:51 PM

For clarification, was there a hole in the sidewall of the tire or did it just blow the bead off the rim?

Tourist in MSN 08-13-12 08:38 AM

Originally Posted by dstke (Post 14595927)
... ... and blew out the bead on the tire. ... ...

Many years ago I had several tires where the tire casing tore off of the wire bead. Is that what you mean - the tire bead stayed on the rim but the tire sidewall blew out?

That batch of tires that I blew out years ago, they were the most expensive tires sold by that bike shop in that size, the shop assured me that it had to be my fault somehow. I then bought one of the cheapest tires they had and it held up just fine. In that case I suspect that I was a victim of a manufacturing defect that somehow allowed the casing fabric to be weakened.

dstke 08-13-12 10:50 AM

Thanos for the replies, especially the link to Sheldon's web pages. I'mpretty sure it's rim heat. Three out of four occurred on steep descents (Jeux-Plane, Stelvio, Fadaia). I've tightened up the drum brake pumping the brakes more than holding firm. It's unnerving knowing it can happen but it's good to now know why.

B. Carfree 08-13-12 07:43 PM

You can always add an "air brake" to your rim brake/drum brake combo. That's where the stoker wears a windbreaker and raises his/her arms while holding the jacket up like a parachute. The person who built our first tandem used this technique when he was riding across the country on an inline quad. He found that two Phil Wood disk brakes (the only kind available back then) and two rim brakes just weren't enough to stop the four bodies on that beast. They used "air brakes" to get down under 40 mph before applying any other brakes. (They would routinely obtain speeds in excess of 70 mph.) We've used this technique on our tandem as well.

By the way, he retired that bike after a severe crash that was the result of a rear tire blow out. No one was seriously injured, but it scared the daylights out of all of them. His twenty-something son is about to bring it back into service because, like all people of that age, he is immortal.

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