The ongoing hookless rims saga

[Spdntrxi]

I for one hope the UCI....does Diddley squat.

[fourflys]

Originally Posted by Spdntrxi

I for one hope the UCI....does Diddley squat.

it would be interesting to know the tire pressure the rider was using when he had that blowout.. as they discussed in the link above, maybe the rider was "old school" and told his mechanics "I always ride 90psi, set the tires to that".. or maybe the mechanics aren't up to speed on the newest stuff if they are a bit traditional as well (or just not as informed as others)..

without that key piece of info (tire pressure being run), we're just blowing a bit of hot air, aren't we?

[Clean39T]

Originally Posted by Spdntrxi

I for one hope the UCI....does Diddley squat.

Same. Every podcaster and prognosticator looking for clicks is crying foul - but this is most likely user error more than anything.

[Spdntrxi]

Originally Posted by Clean39T

Same. Every podcaster and prognosticator looking for clicks is crying foul - but this is most likely user error more than anything.

exactly.. really gets old.

[fourflys]

Originally Posted by Spdntrxi

exactly.. really gets old.

check out the link I posted a few posts ago..

[Spdntrxi]

Originally Posted by fourflys

check out the link I posted a few posts ago..

no thanks..Jimmy is a putz

[rice rocket]

Originally Posted by Spdntrxi

no thanks..Jimmy is a putz

Couldn't agree more.

[fourflys]

Originally Posted by Spdntrxi

no thanks..Jimmy is a putz

meh, to each their own.. I like his take on most things.. he's not trying to be anything other than who he is as a cyclist/human.. so much different than many in the niche..

[MikeD]

In this article https://www.cyclingweekly.com/news/u...ter-of-urgency it was quoted:

Hansen said: “This crash is why the CPA are 100 percent against hookless rims. Tires should not come off a rim. The maximum PSI these hookless tires can have put in them is 73, and if you hit something for sure it goes above the maximum 73 PSI rating on impact. That is why the tires are coming off.”

Is this really true? If you have a car up on a lift and inflate a tire to 35 psi and lower the car so the full weight of car is on the tires, the pressure is still 35 psi. That's because when weight is put on the tire, the casing stretches and the volume remains the same thus the pressure within remains the same. This is pretty much a static case, but in a dynamic situation like hitting a rock or pothole, does the pressure really rise like what is quoted above?

[jimoots]

Originally Posted by MikeD

In this article https://www.cyclingweekly.com/news/u...ter-of-urgency it was quoted:

Hansen said: “This crash is why the CPA are 100 percent against hookless rims. Tires should not come off a rim. The maximum PSI these hookless tires can have put in them is 73, and if you hit something for sure it goes above the maximum 73 PSI rating on impact. That is why the tires are coming off.”

Is this really true? If you have a car up on a lift and inflate a tire to 35 psi and lower the car so the full weight of car is on the tires, the pressure is still 35 psi. That's because when weight is put on the tire, the casing stretches and the volume remains the same thus the pressure within remains the same. This is pretty much a static case, but in a dynamic situation like hitting a rock or pothole, does the pressure really rise like what is quoted above?

I don’t know if true or not, but Hansen has been quoted with some really weird/bizarre hot takes both on this subject and the angled lever thing.

It is hard to know if he is being quoted out of context and he is a undeniably an extremely smart guy but I’ve noticed he has a tendency to take two principles and then say “logically 1+1=2”, when things often don’t work that way and are much more complex.

That gets combined with his fondness for over complicated verbiage and you get left with stuff that’s a bit nonsensical.

[Mark McM]

Originally Posted by MikeD

In this article https://www.cyclingweekly.com/news/u...ter-of-urgency it was quoted:

Hansen said: “This crash is why the CPA are 100 percent against hookless rims. Tires should not come off a rim. The maximum PSI these hookless tires can have put in them is 73, and if you hit something for sure it goes above the maximum 73 PSI rating on impact. That is why the tires are coming off.”

Is this really true? If you have a car up on a lift and inflate a tire to 35 psi and lower the car so the full weight of car is on the tires, the pressure is still 35 psi. That's because when weight is put on the tire, the casing stretches and the volume remains the same thus the pressure within remains the same. This is pretty much a static case, but in a dynamic situation like hitting a rock or pothole, does the pressure really rise like what is quoted above?

Hansen is displaying a common misunderstanding about how tires react to road loads. It is true that pressure increases as volume decreases, but as you note, there is little change in the internal air volume in a tire under load, even if you were to completely flatten the tire against the pavement. Tires support loads not by changes in air pressure, but by changes in the direction and magnitudes of casing forces. However, that's not to say that the changes in casing forces when the tire hits an obstacle might not help pull the tire off the rim. If the tire was already already close to blowing off, hitting an obstacle might cause the casing to be pulled in the right direction and with enough force to pull the bead out of the rim.

[MikeD]

Originally Posted by Mark McM

Hansen is displaying a common misunderstanding about how tires react to road loads. It is true that pressure increases as volume decreases, but as you note, there is little change in the internal air volume in a tire under load, even if you were to completely flatten the tire against the pavement. Tires support loads not by changes in air pressure, but by changes in the direction and magnitudes of casing forces. However, that's not to say that the changes in casing forces when the tire hits an obstacle might not help pull the tire off the rim. If the tire was already already close to blowing off, hitting an obstacle might cause the casing to be pulled in the right direction and with enough force to pull the bead out of the rim.

When hitting a rock or pothole, the tire could "burp." The air rushing under the bead and up the sidewall could help lift the tire bead off the rim I would think.

[glepore]

Well, you do have the case of Sagan's exploding rim...caused Roval/Specialized to pause tubeless for a full year.

And given how firm these tires are to remain on a hookless tubeless setup, I'm not so sure you couldn't see a instantaneous peak pressure spike.

Interesting point made on Geek Warning - the "margin of safety" of these systems is to a fair extent less than the margin of error of most consumer level pressure gauges etc.

If there's no benefit to me and some risk, I'll pass.

[fourflys]

I still say a huge point is we don't know what pressure these tires had in them.. were they following the hookless guidelines? Has there been a verified case of a tire blowing off (not just burping) that were being used as the manufacturer intended i.e. within acceptable pressure ranges?

[glepore]

Originally Posted by fourflys

I still say a huge point is we don't know what pressure these tires had in them.. were they following the hookless guidelines? Has there been a verified case of a tire blowing off (not just burping) that were being used as the manufacturer intended i.e. within acceptable pressure ranges?

In the deGendt case the ETRO spec called for a minimum tire size of 29 and he was using a 28, so that's likely contributing at any pressure. But the 28 on that wheel measures 30 something, so confusing. And the next "sponsor appropriate" tire was a 32, so too big. But its this kind of stuff that makes it difficult.