Tubeless conversion disaster

That should not happen at 80psi. Francis Cade made a YouTube video testing tyres pressures before the rim pops and they were almost twice as you before something happened.

How would this be possible?? Iā€™m not saying it couldnā€™t be but how would you not design a kind of bleed port into your rim if there was a possibility that you could start pumping air into your rim. If this is actually the case then this seems like an extreme oversight from an FMEA perspective.

Without looking at the damaged wheel in person, itā€™s hard to say exactly what happened in this particular case. The pics above look like the rim blew out.
Out of the 5 different wheelsets Iā€™ve got banging around, only 2 have obvious pressure equalisation ports in the rim. The ports are only small anyway so it wouldnā€™t be too hard to have one seal up whilst trying to seat a stubborn tyre.
I suppose the others rely on air escaping past the valve (provided you havenā€™t sealed the outside with the o ring and some sealant).

IME with TL rims itā€™s quite common to have sealant leak into the rim where the valve is tightened against the rim tape/rim. Every valve seems to have a different design and some fit better than others.
The other area that can leak is where the tape covers the spoke access holes. Some TL rims donā€™t have these holes, or the need for tape of course, so that oneā€™s rim dependant.

Yeah I understand that itā€™s pretty common that air can get under the tape and then into the rim through the nipple holes in the rim bed or the valve stem hole. My point was more that it seems like a serious design oversight if that isnā€™t considered by Flo or other rim makers where enough air at a high enough pressure can make itā€™s way into the rim without a purpose built way for it to escape so that it doesnā€™t blow out.

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I totally agree! The thought of a rim blowing out is pretty terrifying.

I suppose they could make a larger hole in the rim somewhere and cover it with a sticker to stop water ingress. Print some warning text on it and Bobā€™s your uncle.
No more catastrophic failure due to a sudden increase in internal rim pressure. Be it from a leaky valve, or something like a cracked rim.

You can buy tubeless valves that are designed to vent any air pressure from within the wheel!
ā€œPlease note: The Pressure Release Valve Stem Nuts have been designed to allow the air to escape if it breaches the tubeless tape, if you notice air escaping through the valve, your tubeless tape has not been correctly installed.ā€

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On the TR rims I have, I canā€™t see how pressure could build up in the rim when there are a bunch of spoke exit holes that arenā€™t air tight.

Iā€™ve had a damaged spoke put a hole in my tape and had sealant & air go into the rim before, but there was no way the sealant was going to seal every spoke hole before the tire lost all the air. I guess maybe if you just continued to pump it with a compressor all the spokes holes might eventually seal and pressure would build? Iā€™m not doubting itā€™s a thing since stanā€™s has valve cores to address the issue, I just donā€™t understand how it happens.

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It depends on the wheel design.
Some wheels have spikes that are attached to the innermost surface of the wheel. Some have a shallow wheel with a carbon fairing.

Iā€™ve seen a Reynolds wheels with this same problem where the rim tape failed during tire installation and the rim itself started pressurizing.

Good find. Although, I can tell you from experience that sealant will most likely block them over time and render them useless.
I often have to take out the valve cores and ream out the valve body itself. Itā€™s also not uncommon to find a bit of sealant stuck to the part that goes through the rim.

Everybody seems to remember that one time when sealant sprays all over the place from a tiny hole that shouldā€™ve sealed. Itā€™s easy to forget that it often seals things without you noticing.
Possibly during your first 2hr stubborn tire installation? :tired_face:. I donā€™t know. Maybe.

Who knows why the OPā€™s rim actually failed. It mightā€™ve already been damaged, or had issues with the spoke tension. No matter what caused it, it sure looks like the air pressure blew out the whole side of the rim as it failed.

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Yeah, I had the same, a nail or somethjng punched through my tyre, rim tape and rim, and all that happend was that I couldnā€™t pressurise the tyre at all, until I found the hole and put new rim tape over it.

Even in the picture above, it looks like sealant has come out of the spoke holes, so presumably air will come out too - but maybe sealant can block those holes if the tolerance is small, and then you create a pressurised rim.

I canā€™t see how you could blow out a rim outside of the scenario in the OP, when trying to seat a tyre and have a pump or compressor attached. Later on, even if the tape fails, leaking air into the rim would increase the volume, which means the pressure will drop.

Thatā€™s incredible customer service.

Hearing something like that definitely puts Flo on the radar for new gravel bike wheels that Iā€™m starting to look around at. A company who is willing to stand behind their product like that is incredibly solid.

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I hear you. Thereā€™s not a single rim that I own that Iā€™d lose sleep over. (Mostly XC duty).
However, the rim above is shredded. The walls seem to be quite thin and have a large surface area.
Try this scenario:
You pump up your wheel just before a ride and the rim is pressurised along with the tyre.
It doesnā€™t fail immediatelyā€¦

Donā€™t get me wrong. Tubeless is awesome, if done properly.

Ah, yeah, good scenario. I do wonder if they take that into account though - usually there is a pressure limit on the rim.