PeteHski

The pressure trying to blow the tyre off the rim is acting over a larger surface area with a wider, higher volume tyre. This larger surface area leads to a higher force at the tyre bead. Force = Pressure x Area. The area in this case is the internal surface area of the tyre.

So for example if you double the tyre internal surface area, then you double the force acting on the bead at the same pressure. Pressure is just force per unit area.

Kapusta

Disclaimer: I did not read past the 1st page of comments.

Just chiming in to say that what Hunt is claiming is true. Higher volume mean more bead stress at the same pressure.

I can see someone who is not so familiar with tubeless making the OP’s error. Being a bit more familiar with this stuff I would not pump a 38mm tire up to 80psi tubeless unless I had some clear documentation that both the tire and rim could handle it. I almost reached to plug my ears and shield my face when I read your opening sentence.

I do think these things need to be more well and explicitly labeled right on the rims, the same way max tire pressure is labeled on tires. It should give max pressure at a few different tire sizes. IF the rims just say “100 psi max” that is misleading , IMO.

Koyote

"I'm gonna assume a whole bunch of stuff that confirms my uninformed bias."

terrymorse 

It's not the air pressure that stresses the rim, it's the force of the tire trying to pull away from the rim.

If the tire has a bigger circumference, the "pull away" (circumferential) force will be higher.

t2p

Alfred Hitchcock warned us about carbon rims

just sayin

Racing Dan

Well, you should Always adhere the the max pressure of either the rim or the tyre, whichever is higher. HOWever , what good is it your tyre wont seat at the rim max pressure. That seems to be the case in this instance.

Thus, Imo, engineering a rim with at 40 psi (2.76 bar) max pressure is simply fail and a free replacement is justified. - Sadly, replacing the rim with another identical rim is likely to leave you in the same situation, next time around.

79pmooney

Paint 'em with silver paint. The birds will go for someone else's wheels.

Kbarter

I have commuter that will look great with carbon rims on it. The replacement rim did arrive 3 days after I heard from them, will get it rebuilt in a few weeks.

I have definitely learned a good bit on the thread !

79pmooney

Well, there's choosing components that work well for their intended use. Manufacturers should be helpful here but there is a long history in bicycling and elsewhere where they aren't. Knowledgeable shops are an asset. So is buyer awareness. I am often wondering "why don't ...". Here, why don't rim manufactures give a biggest recommended tire along with max seating pressure allowable for that rim? (Maybe they do. I haven't done tubeless and have in fact gone away from clincher tires entirely.)

Of course, required seating pressure is a function of both the rim and tire. The rim manufacturer has no say in the latter.

Or ... maybe some bright engineer needs to come up with a non-air pressure means of seating tubeless tires; allowing bigger tubeless tires for marginal rims. Perhaps in 20 years, folk will be saying "remember when they use to inflate tubeless tires to insane pressures to seat those beads? All the blown sidewalls and eardrums? Thank God we have our BeadSeater." Or ... ding, ding! You could remove the flanges entirely, make the entire rim a little bigger in diameter to raise up the lower portion to use existing tire sizes, then glue! a tire that's already been sewn or formed into a tube. No rim failures at any pressure. With all the modern adhesives, this should be easy.

terrymorse 

Fixed.

PeteHski

Well there is this option:-

https://www.bicyclerollingresistance...oria-air-liner

“The first problem the Air-Liner Road solves is inflating tubeless tires, which can be a real problem with some tires and rim combinations. The Air-Liner solves this problem by making sure the beads are pre-seated and inflating the tire becomes extremely easy.”

terrymorse 

I struggle to see how that tire insert would manage to seat a tire bead. It ought to function during installation about the same as a slightly inflated inner tube, which experience shows that it does little to help seat a bead, but it does make it harder to install the tire.

PeteHski

I can’t say I’ve ever used them or had any issues seating tubeless tyres. To be fair, the review does talk about a “tip” of pre-seating the tyres before adding the insert, so I guess that negates any advantage they may have in seating the beads.

Racing Dan

Brain fart. Thanks!

Racing Dan

Obviously both tyres and rims need to cope with seating pressure, that is much higher than average riding pressure.

Atlas Shrugged

The incident under consideration involves a circumstance hitherto unencountered, encompassing five pages of documentation and eliciting 115 comments. Noteworthy is the fact that the application of tubeless tires to carbon rims, a practice that has seen widespread adoption, has heretofore demonstrated an absence of notable incidents. It is plausible to posit that the occurrence in question may be an isolated event, and the prevailing consensus suggests the continuation of routine practices. Furthermore, given the unique nature of this specific case, it is conceivable that the tire pressure exceeded the value indicated by the original poster. In light of this analysis, I am inclined to persist in my established approach, affording minimal consideration to this singular occurrence.