A simple slide guide to tubeless and hookless

[MikeD]

Originally Posted by Baron Blubba

Sigh, I should have known this would cause another tubeless spitstorm.
[/I]

When I saw that photo without reading, my first thought was, "That poor bastard forgot to tighten his quick release and his wheel separated from his bike!"

[Baron Blubba]

Originally Posted by MikeD

When I saw that photo without reading, my first thought was, "That poor bastard forgot to tighten his quick release and his wheel separated from his bike!"

Excuse me, we’re fighting about tubeless here. Save your QR disparagement for another thread.

[Mark McM]

Originally Posted by NHAero

Isn't that table for straight sided (aka hookless) rims?

Yeah, sorry, another example of my fingers typing faster than my brain can think. The original post has been corrected.

[reuben]

Originally Posted by Baron Blubba

Sigh, I should have known this would cause another tubeless spitstorm.

Sadly, that was my first thought when I saw this thread. The internet is where good deeds are often punished, where experts abound, and a counterexample can be found to disprove anything.

[reuben]

Originally Posted by Baron Blubba

Excuse me, we’re fighting about tubeless here. Save your QR disparagement for another thread.

OK, that made me laugh, in a sad.sort of way. Well played, sir, well played.

[oldpotatoe]

So...I've been away for a while..somebody tell me again...why are manufacturers making hookless rims?
Better? Cheaper? More reliable? Faster?

[Xrslug]

For the engineering-minded here (not me) — one of the things about road tubeless on hookless rims that I’m wary of is the much smaller difference between optimum pressure and maximum permissible pressure for tubeless-specific tires as compared to clinchers. On a gravel bike (and definitely MTB), lower pressures are the norm, so this seems like less of an issue but preferable road PSI seems extremely close to maximum tubeless tire PSI.

So if I’m understanding what I’ve read (questionable), with clinchers intended for hooked rims, the ISO standard says the pressure limit (I’m assuming before tire blow off becomes a risk) is 1.5 times the maximum stated tire PSI, whereas for hookless-specific tires, *the pressure limit is 1.1 times* the maximum stated tire PSI. So if the max stated PSI for a hookless tire is 76 PSI, the ISO pressure limit before risk of tire blow off could easily be exceeded just using a slightly inaccurate floor pump.

More to the point — how does pressure in a tire work? I’m assuming that when we hit a square-edged hole that deforms the tire, the internal volume of the tire is momentarily decreased but the volume of air remains the same, leading to a spike in air pressure inside the tire. If that is correct, and the ISO pressure limit is only 1.1x, isn’t it likely to be routinely exceeded just by riding on rough roads?

[gravelreformist]

Originally Posted by Xrslug

For the engineering-minded here (not me) — one of the things about road tubeless on hookless rims that I’m wary of is the much smaller difference between optimum pressure and maximum permissible pressure for tubeless-specific tires as compared to clinchers.

If I’m understanding what I’ve read (questionable), with clinchers intended for hooked rims, the ISO standard says the pressure limit (I’m assuming before tire blow off becomes a risk) is 1.5 times the maximum stated tire PSI, whereas for hookless-specific tires, *the pressure limit is 1.1 times* the maximum stated tire PSI. So if the max stated PSI for a hookless tire is 76 PSI, the ISO pressure limit before risk of tire blow off could easily be exceeded just using a slightly inaccurate floor pump.

More to the point — how does pressure in a tire work? I’m assuming that when we hit a square-edged hole that deforms the tire, the internal volume of the tire is momentarily decreased but the volume of air remains the same, leading to a spike in air pressure inside the tire. If that is correct, and the ISO pressure limit is only 1.1x, isn’t it likely to be routinely exceeded just by riding on rough roads?

You've pretty well got it. Some manufacturers like Giant seem to indicate that they test their hookless tire/rim combinations to 150% - but it's not even clear with Giant whether that truly applies to hookless (this page is linked from their hookless info page - but nowhere on the page does it specify if the content applies to both hooked and hookless or not.)

The question of what happens when the tire is impacted seems still up for debate - at least on Internet forums. Giant does make the claim that an impact will cause a pressure spike, and I'm inclined to believe them and it seems to logically make sense.

The problem is that both the margin of safety is way too low and tire QC standards are way too lax. I've installed two sets of GP5000 tires on one set of rims - the "S TR" models required a bead jack and much sweat to install. The "AS" model went on so easily by hand that there is no way I'd ride that tire if I didn't have a hook and be riding them low pressure.

[makoti]

Originally Posted by oldpotatoe

So...I've been away for a while..somebody tell me again...why are manufacturers making hookless rims?
Better? Cheaper? More reliable? Faster?

I'll take door #2, Bob. Cheaper

[fa63]

Originally Posted by Xrslug

More to the point — how does pressure in a tire work? I’m assuming that when we hit a square-edged hole that deforms the tire, the internal volume of the tire is momentarily decreased but the volume of air remains the same, leading to a spike in air pressure inside the tire. If that is correct, and the ISO pressure limit is only 1.1x, isn’t it likely to be routinely exceeded just by riding on rough roads?

The volume is not really decreased per se; the tire deforms and the volume should stay the same. I imagine there might be a localized spike in pressure due to rate effects from a rapid impact.

[AngryScientist]

Haha,

the "simple guide"

[MikeD]

Originally Posted by fa63

The volume is not really decreased per se; the tire deforms and the volume should stay the same. I imagine there might be a localized spike in pressure due to rate effects from a rapid impact.

I think what is happening is you hit a rock, the bead gets pushed off the bead shelf (burp), the rush of air under the bead and up the sidewall lifts the bead off the rim. Probability a tubeless phenomenon, irrespective of hooked or hookless. Instant flat regardless.

[Dave]

I don't believe that it's accurate to say that a blow off is likely at 80 psi on a hookless rim and tire setup - that's 1.1 times the 73 maximum. Enve has seen tires go up to 140 psi before blowoff occurred. I've taken several setups to 85, just as a test. My normal pressure is 52-55. I do go to the effort to calibrate my pump gauges. My old Silca pump was reading 8psi higher than actual, so it got the tiny 0-160 gauge replaced with a much larger 0-100 model. I also check a new pump against my gauge standard.

As for why hookless, it's most likely to reduce scrapped rims due to hook defects and to simplify the molds.

[Baron Blubba]

2 more comments then I'm out of here.

1. Those slides in the OP were meant as a PSA to my customers, a reminder that 'hey, if you have tubeless or hookless tubeless set ups, there are some guidelines to follow.'

2. I see the fact that hookless is cheaper spoken of disparagingly. The fact is, outlying ultra-boutique brands notwithstanding, entry, mid, and high end carbon wheel prices have remained stable or decreased over the last several years. People frequently (myself included), very often justifiably, ridicule or complain about about the obscene prices of bikes and bike parts. If manufacturers have found a way to stabilize or decrease wheel prices, isn't that a good thing?
And here are the sentences that are bound to be ignored: Obviously, if hookless proves to be a significantly greater safety hazard, a safety hazard which is unpredictable and cannot be mitigated through proper education and procedure, then yes, hookless is a bad thing, no matter how much money it saves the manufacturers and consumers.

Personally, I'd estimate that I've ridden ~100k miles on tubeless, with probably half of that or more being on hookless tubelesss, and have never ever had an incident.

Then again, nothing is ever broken until it breaks.

Then again, I've also got hundreds of customers riding the stuff and in all that time only one failure which was not due to a tire blowing off a rim, just a tire falling off a rim. Which could happen with any sort of rim/tire combo.

So I remain confident.

[Likes2ridefar]

FWIW #1 was very clear and I feel your frustration