coker tire damage from blown out 29er tube

After trying out a 29er tube conversion for the first time and feeling pretty good about the results, the tube blew-out today, pulling one side of the tire partially off, leaving shredded tube hanging over the side of the rim (and causing a small panic in my office. Yes, not only am I the wierd guy that rides a huge unicycle, but now I’m that wierd guy that caused the code 5/guns drawn response from building security for a “gunhots fired event” inside the building). Anyway, I wasn’t riding at the time, so no UPD.

I’m running a Radial TA tire on a new Airfoil rim. Tire has 700 miles on it (wheel has zero miles). I followed U-Turns 29er directions and used John Child’s strapping tape idea too. Tire went on the rim pretty easily with the wood clamps and Schwalbe slippery tire mounting goo.

I am not sure how blow-outs effect this rim and/or tire. Should I expect that the tire is not going to hold again and I should replace it? Are future blow-outs less likely with tubeless or stock coker tube?

It sounds like a bit of the tube got stuck under the tire, pulling it up, untill the critical point was reached where the tire slipped over the rim. It probably shouldn’t affect your tube, seeing as I highly doubt the bead was stretched.

Causing a ‘guns fired’ response from building security with a unicycle is a first though, I think.

This is the first I’ve heard of this type of problem for either tire.

Please explain about the Schwalbe goo.

Was the tire previously on an Airfoil rim (for the first 700 miles)?

What tire pressure did you have at the time of the blowout?

Did you do any riding on the new setup or did it blow before you rode it?

Your just not having the best of luck with this Coker are you?

And as for you actual question. No i dont think your tire is damaged. I work in a bike shop and people come in with blowout all the time and its almost never serious enough to kill a tire.

But on a side note we did one time blow a sidewall off a rime with a tube…


U-Turn’s questions:
The Schwalbe goo is the tire bead lube they sell in a plastic bottle with a sponge applicator. Kind of a soap solution, but evaporates quickly and leaves a slippery residue.

Tire was on a stock steel rim previously.

Tire pressure was around 60PSI or so, but I have ridden with this tire at 60 PSI on the old rim for many months with no problems.

I’m having some other issues with my frame, so it blew before I could even go for a ride.

The tire install was easier than I thought it should have been. I used some clamps and took my time. Maybe the tire bead was stetched out already? I was really careful to visually check the inside of the bead all the way around to avoid a piched tube. It held air for two days before blowing. It was never left in a hot car or even outside.

I’m tempted to install a stock coker tube so I can get out on the road, but if the tire won’t hold, I loathe blowing through any $15 tubes, that I think are not available right now at UDC.

Any ideas? Will tubeless help or make blow-outs like this less likely.

Check that the steel bead is not damaged. Vigorous tyre installation could snap the bead- causing it to have a weak spot that lifts off the rim and let’s the tube herniate through. That’s what happened to me last year when I went back to a tubed Coker for a while- the tyre lifted off and blew up the night before a 106km Bike Race I was doing. Had to call Andrew Carter wondering what my chances are of getting a Coker inner tube in Toowomba (small town in the middle of nowhere). I reinforced another inner tube with duct tape and superglued the tyre onto the rim- it held up for the 106km race but I wouldn’t recommend it.

You can tell the bead might be damaged if your tyre slips onto the rim much easier than you’d expect.

I’m giving up on the 29er tube idea for a Coker tire.

I had to replace my 29er Coker tube due to a puncture (due to a thorn) and since then I have had nothing but problems with the 29er tubes. I had 3 Schwalbe 29er tubes on hand after that flat. I now have zero 29er tubes. I’m out of 29er tubes and all of them have failed. I’m back on a standard Coker tube now.

One of my 29er tubes failed when I inflated it to stretch it out. It quickly developed a hernia and exploded within a few minutes. The next tube seems to have gotten pinched during the install, but I was extremely careful during the install so I don’t know what’s up with that. The next tube worked for a couple weeks or so, but began losing air. I removed the tube and found no obvious holes. I dunked the tube in water and found a spot where the rubber was very thin and the air was escaping. Not a hole, but the tube wasn’t holding air. Maybe that was due to the tube getting pinched during install, or maybe it was due to a defect in the tube at manufacture. Anyways, that drained my supply of 29er tubes so I’m back on a Coker tube. I actually have three Coker tubes on hand so I’m all good.

I don’t think I’m going to go for the 29er tube idea again. If I try anything new it will be a Stan’s tubeless setup.

I’m not surprised that the tire was on a stock rim. I’d save myself a lot of frustration and ditch the tire and start fresh. New wine, new wineskins kinda thing.

As far as a broken bead wire - experiments that cut bead wires in 1" pieces have shown that that’s not a reason for a blowout.

I don’t think this is common at all, given the many miles that my customers have put on their LiveWire wheels with 29er tubes installed. The problem is using a tire that had many miles on it with a different rim. Replace your tire and and start with a fresh mind.

No- I have to disagree there- once my Coker bead wire started fraying, there was no way of getting the bead back on securely- the bead popped over the rim as I was riding. I watched in horror :astonished: as the tube then ballooned out from under the bead and EXPLODE very loudly. If you see that happening make sure you run away as quickly as possible and put your hands over your ears.

With the slippery Schwalbe goo (say THAT 3 times) and 60psi, and the possibility that the tire may not have been exactly centered on the rim, maybe that combination caused the tire to “wander” off the rim?
Not many folks are willing to run 60psi on a tire rated for 32. Maybe try 40 to 50 for an added measure of safety??

And since others are chiming in, mine is that I’ve never had a pinched tube or flat with a Bontrager 700c x 35-42mm tube, on either the coker tire or TA.
JC, does this mean we can go back to storing our ride drinks in your leakproof tube?

I pump up the tire to about 60 psi when seating the tire. I pump it up, let it sit for a while, and the tire seats itself evenly around the rim. Then I go down to about 45 psi for regular riding.

I wonder if that high psi seating is damaging my delicate 29er tubes?

I use to use silicone spray on the bead to make the tire easier to seat and easier to get on the rim. I didn’t use the silicone spray this time because it’s in storage and I’m too lazy to dig it out or buy a new can. Maybe the lack of silicone spray made the seating process more abusive to the tube when the tire finally slipped into place?

I’ll put Everclear in the Coker tube now. The Coker tube is burly and can handle the alcohol.

i haven’t been able to ride my “coker” because the stock tube failed almost 2 months ago. i wanted another 36" tube but i kept getting backorders, so i bought some 29er tubes from schwalbe just to be able to ride again. i’ve been going crazy without my unicycle. i’m installing the new tube tonight. i was already feeling uneasy about the whole 29er thing, so this is not what i want to hear…

Yes, but the issue you originally raised was a “snapped bead”; see the following quote

A shape-changed bead surface could allow the tire to slip off at that point. The test I mentioned was investigating the effect of a wire that was not whole.

Boo — I’m in Texas too; next time let me know (if you like) if you need something. I have tubes here of both sizes.

:thinking: I don’t get it Dave- the bead frayed and basically loosened because of that. Are you saying that if you made a clean cut of the bead on a Coker tyre that the same thing won’t happen?

Bags not being your test pilot :stuck_out_tongue:

man i should’ve thought of that.

JC, I think you followed that process in installing the 29-er tube on my coker wheel, and there were no ill effects. That original 29 tube (installed first time with no leaks) is still going strong 724 miles later. Knock on my wooden haid.

Manufacturing defects tend to come in clusters, and if not caught, clusters tend to ship together. I wonder if it’s possible you just got a bad set of three or four tubes. Next time we ride, I’m happy to lay one of mine on you if you want to try one more time. Maybe I got a cluster of good ones…

I estimate the stored energy of a Coker tube at 60 psig (5 bar absolute) to be about 2 kiloJoules. The stored energy in a .45 ACP round or an M-80 are both about 1 kiloJoule. I have heard a bicycle tire explode in my basement (a nice, confined area) at about 100 psig and it is similar to a gunshot. This kind of shock hurts the ears…I mean pain.

I spend time making each rim tube-friendly before I do a build, and that’s probably a factor here, Tom. I bevel and smooth the valve stem hole, sand off any rough places on the rim internal surface, and go over the bead surface to ensure that it is uniform. A more-thinly stretched tube will be more easily damaged for the typical wheel that is not prepped this way. See here.