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Tubeless tire blows off rim?

Old 05-29-16, 08:15 AM
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Tubeless tire blows off rim?

I was on one of our MUPs yesterday and passed a woman on a great Trek endurance road bike, looking forlornly at her front wheel. Stopping, she told me the bike is brand new and the tire just blew off. I tried to re-engage the beads and pump it back up, and had success with the beads, but only moderate success with the pump. End of story, she was better able to walk the bike to her car and take it to the LBS.

What allows a tubeless tire to blow off? Are they more susceptible to beads releasing from the rim than tubed road tires?
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Old 05-29-16, 09:22 AM
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Properly mounted? Excessive pressure past the limit of the tire (just like a standard clincher).

More likely causes? Not using a true tubeless tire--especially with high pressure tires, Kevlar beads are insufficient to hold the tire on...steel or carbon fiber beads are necessary.

Mounting a tubeless tire on a non-tubeless rim can also do it, as there is nothing on the rim to retain the tire other than pressure.
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Old 05-29-16, 09:48 AM
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So a tubeless rim needs a more aggressive bead hook that matches a stronger and stiffer bead than you find on a Kevlar-bead road tire.

When I re-mounted her tire the beads felt rather flexible - maybe they were Kevlar, but I didn't really notice. I thought the force required to get the bead into the rim was too low - it was too easy!

Also the sealant was rather "juicy" inside the rim. I wonder if it could have leaked onto the bead/rim interface and lubricated it, so that the tire just oozed off due to the pressure.

I don't have any idea if the rim had the proper bead. Bike was new and had just been delivered to her by the Trek dealer, so she did the right thing by heading promply back to the LBS.
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Old 05-29-16, 11:27 AM
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Originally Posted by Road Fan
So a tubeless rim needs a more aggressive bead hook that matches a stronger and stiffer bead than you find on a Kevlar-bead road tire.
No, a standard road clincher rim will work just fine with road tubeless (assuming the proper preparation to make the rim air tight, etc), the key to road tubeless is the tire. Most road tubeless tires have a carbon fiber bead, you rely on the bead of the tire to keep the rim/tire interface air tight. But again, with road tubeless, it's the tire, not the rim, that has to be truly "tubeless compatible," i.e., designed specifically to be run tubeless.

With mountain tubeless and even cx, it's sort of like the wild, wild west, you just play around with stuff and make it work if possible, lots of methods, lots of variables, lots of non-tubeless specific tires end up working just fine. But NOT with road tubeless, even with reduced pressure from what you would typically run in a regurlar, tubed road clincher, the pressures are just too high for the bead to remain air tight without a tire bead specifically designed for it.

When a tubeless tire blows off the rim, whatever the root cause, what has happened is that air has abruptly escaped the bead and the force has "blown" the bead, and tire, off the rim. Very often, the tire is ruined.

Too many possibilities and variables to make a guess at what happened in the situation you describe.
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Old 05-29-16, 11:57 AM
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Ok, thanks! Seems like there are several things the LBS could have messed up. Regardless, the bike needed to be returned to the shop.
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Old 05-29-16, 12:21 PM
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Every time I read a thread about road tubeless, I get more convinced to never try it.
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Old 05-29-16, 04:33 PM
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Originally Posted by jyl
Every time I read a thread about road tubeless, I get more convinced to never try it.
Good advice. It's goes a little deeper than mine, which is, if you need the shop to set up and maintain your tubeless wheels, you shouldn't be using it. Especially if some part of your setup isn't fully tubeless ready. Tubeless ready tires are smooth, not textured at the bead and the casings are less porous.

Chances are that a mistake was made seating the tire, but you'll never reseat the bead with a frame pump. That takes a high-pressure rapid inflation from a compressor. The proper way to deal with a tubeless mishap is to install a tube, inflate it, and ride on.
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Old 05-31-16, 03:42 PM
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Originally Posted by jyl
Every time I read a thread about road tubeless, I get more convinced to never try it.
Every time I read a thread about tubeless, I stay convinced to never try it.
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Old 05-31-16, 03:49 PM
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In the OP's case....I'd suspect either a bad rim or a bad tire. The tire being bad from the factory, or because a rookie wrench country-boy'd the bead mounting it. The tire should have seated when being ridden, it might have burped and lost a bit of pressure but it should have seated.

Originally Posted by oldbobcat
Good advice. It's goes a little deeper than mine, which is, if you need the shop to set up and maintain your tubeless wheels, you shouldn't be using it. Especially if some part of your setup isn't fully tubeless ready. Tubeless ready tires are smooth, not textured at the bead and the casings are less porous.

Chances are that a mistake was made seating the tire, but you'll never reseat the bead with a frame pump. That takes a high-pressure rapid inflation from a compressor. The proper way to deal with a tubeless mishap is to install a tube, inflate it, and ride on.
Depends on the tires and rim. If the tire is tight on the rim to start with (AKA a massive bear to get on) and fairly narrow, a floor pump can probably probably seat it if you rapidly pump it up with a good floor pump. On my Belgium+ hoops, with 23mm Schwalbe One tires I can seat them with a floor pump, but the Schwalbe One 25s and 28s require a compressor shot.


Originally Posted by dsbrantjr
Every time I read a thread about tubeless, I stay convinced to never try it.
It can be a hassle for not much. I recently went back to roadie tubeless on my rear by accident...ordered the tubeless version instead of the tubed clincher. No biggie as I still had tubeless tape on the rim.
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Old 05-31-16, 04:14 PM
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Originally Posted by Marcus_Ti
On my Belgium+ hoops, with 23mm Schwalbe One tires I can seat them with a floor pump, but the Schwalbe One 25s and 28s require a compressor shot.
Or one of these: Lezyne - Engineered Design - Products - Floor Pumps - High Volume - Pressure Over Drive
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Old 05-31-16, 05:51 PM
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When I was setting up my wife's mtb as tubeless (a mid-to-high-end full-suspension mtb that came with "tubeless ready" wheels/tires), I blew one tire off the rim because I was careless with the compressor and went over the max pressure. Obviously I don't know how much over (if I had been paying attention I wouldn't have gone over!) but I estimate I was running 90 in a 65.

Then when I was trying again, I got it to seal (without a compressor), and was using the floor pump to bring it up to 60 to sit and cure for a while...

It blew off at 58. Obviously, the (folding) bead had stretched from the first blowoff.

That was the end of that experiment. My wife now rides with one tubeless wheel, and one tubed. I'll try again when she wears out that tire.
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Old 05-31-16, 06:53 PM
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Originally Posted by RubeRad
When I was setting up my wife's mtb as tubeless (a mid-to-high-end full-suspension mtb that came with "tubeless ready" wheels/tires), I blew one tire off the rim because I was careless with the compressor and went over the max pressure. Obviously I don't know how much over (if I had been paying attention I wouldn't have gone over!) but I estimate I was running 90 in a 65.

Then when I was trying again, I got it to seal (without a compressor), and was using the floor pump to bring it up to 60 to sit and cure for a while...

It blew off at 58. Obviously, the (folding) bead had stretched from the first blowoff.

That was the end of that experiment. My wife now rides with one tubeless wheel, and one tubed. I'll try again when she wears out that tire.
From what you're saying, you're missing most of the point of what running tubeless mountain bike tires is about. With mountain bike tires, one of the biggest advantages of tubeless is running lower pressures than you'd be able to get away with if you were using inner tubes. Forget about what the max pressure on the sidewall of a mountain bike tire you're going to run tubeless says, for that matter, the minimum recommended pressure can often be ignored, too. 40 psi is at the very upper end of what you should ever run in a mountain bike tubeless tire, and much, much less is where the real advantage is. Any more than about 40 psi on a tubeless mountain bike tire and you run a very real risk of blowing the tire off the rim with most tire/rim combinations. On my regular mountain bike with 29 x 2.2 tires, I run about 26psi in front, 28psi in back, and this is fairly typical of what most riders run pressure-wise with tubeless tires of this size. The tires soak up the trail, provide great traction, there's no chance of a pinch flat, and with liquid sealant most small punctures are sealed within seconds.
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