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Zipp "reaffirms" safety of its hookless rims, but now advises teams to use tyres no smaller than 29mm

Zipp’s latest statement continues to claim "unfortunate impact failures" that could happen with any rim/tyre combo were to blame for two separate incidents at the UAE Tour and Strade Bianche, where the riders’ tyres completely detached from the rim

In the wake of the recent controversies surrounding hookless rims, Zipp has released another, more comprehensive statement "reaffirming" the safety and integrity of its products. The announcement comes after incidents at the UAE Tour and Strade Bianche, which raised concerns about the structural stability of Zipp's 353 NSW front wheels and hookless rim designs in general, with Zipp claiming its own internal testing, statements from the riders affected and footage confirmed that "major impact forces" were to blame. The brand has, however, advised teams to run tyres that are at least 29mm wide going forward. 

The tumultuous aftermath of these crashes, including Thomas De Gendt's mishap at the UAE Tour and Johannes Adamietz's similar incident at Strade Bianche, prompted Zipp – and Vittoria, whose tyre was used – to release statements declaring the events had no connection to hookless rims or the tyre used. Since those, Zipp has taken the two front wheels into its Indianapolis labs to conduct thorough reviews and investigations. Now publishing the results, the company has concluded that both crashes were directly caused by "major impact forces"; in other words, we suspect this could refer to rocks or other objects on the road.

Zipp said this is backed by race video footage, statements from Thomas De Gendt, Johannes Adamietz, the Lotto DSTNY team, its own internal impact and inflation testing of the tyre and wheel combination, and dissection of the 353 NSW wheel returned from the Lotto DSTNY team at the UAE Tour. 

Johannes Adamietz's hookless incident at Strade Bianche

Though the not-so-eagle-eyed were able to see the object causing the impact, with the statement Zipp aims to put a stop to suggestions that the crashes were due to a mismatch between the 25mm internal rim and the 28mm Vittoria Corsa Pro tyre instead. According to ISO standards, which were updated in summer 2023, the Zipp 353s, having that rim width, are recommended to only be used with tyres of 29mm or wider. 

> Pro cyclists’ union “not happy” with hookless wheels after “freak” blowout causes Thomas De Gendt crash

These changes to the ISO standards should have been communicated to all teams racing at UCI-sanctioned events before the 2024 season started, but to drill the message in, the UCI also "decided to study the situation as a matter of urgency with a view to taking a rapid decision in the interest of rider safety." 

Zipp rim detail

Zipp now recommends pro teams follow the recommended standards:

"While the combination of 28 mm label tyres with a 25 mm internal rim width was an ISO-approved combination until recently and has been raced safely in the peloton for three seasons now, we are advising all of our teams to strictly adhere to the ISO tyre and rim compatibility chart out of an abundance of caution - all of our teams will be advised to run no smaller than a 29mm label TSS-compatible tyre on our 25mm internal rim widths."

Zipp continued to state that the incidents had no connection to the wheels' construction: "Our carbon laminate dissection showed the wheel construction met Zipp’s prescribed carbon laminate design and processing standards, reassuring that unfortunate impact failures could be expected with any carbon wheel product regardless of rim type or tyre size. Both breakages were wholly unrelated to the hookless design of the rim or the tyre and rim width combination."

The brand also remains steadfast in advocating hookless wheels, listing reduced retail prices, easier tubeless installation, lighter weights, and superior performance as their benefits.

What does this mean for customers?

Of course, it's not just professional cyclists using Zipp's hookless wheels, and since we first published this article questions have been raised over what this latest advice might mean for customers. 

While Zipp insists the 28mm tyre/25mm internal rim combination was not the cause of the UAE Tour and Strade Bianche incidents, conversely it is now advising pro teams to run "no smaller than a 29mm label TSS-compatible tyre" out of "an abundance of caution". 

At the time of writing, it doesn’t appear that this advice extends to owners of Zipp's hookless road wheels. Zipp’s compatibility chart currently recommends many tyres below 29mm on its 25mm hookless rims, and as narrow as 27mm in the case of the Challenge H-TLR Criterium RS.

We've asked Zipp to clarify its position, and whether all owners are also advised to run tyres with a minimum stated width of 29mm going forward, and will update this article when we hear back. 

Suvi joined F-At in 2022, first writing for off-road.cc. She's since joined the tech hub, and contributes to all of the sites covering tech news, features, reviews and women's cycling content. Lover of long-distance cycling, Suvi is easily convinced to join any rides and events that cover over 100km, and ideally, plenty of cake and coffee stops. 

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36 comments

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jonwolds | 2 days ago
0 likes

SRAM English compatabilty chart has removed 28mm as compatible with 303FC. The version linked in the article still shows them as compatible.

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MattieKempy | 2 months ago
4 likes

The catastrophic crashes I've had have been caused by potholes (broken rim), diesel (concussion) and a blow-out  resulting in a snapped frame on a hooked, carbon tubless-compatible rim with a 25mm tyre and correct-sized latex tube, at about 45km/h. Yes, it hurt, thanks for asking. I've since ridden hookless carbon rims for as many km as I have hooked carbon rims with precisely no problems or worrying whatsoever. Yes, I run 35mm tyres at about 45psi and I take care to make sure they're hookless-compatible, but then I took care to make sure my tyres were compatible with my rims and pressures previously, especially since I've been running tubeless for nearly 10 years despite the doomsayers telling me that the world would end if I carried on. If you do what you're supposed to then you didn't ought to have any problems!

There is no reason to suppose, given the testing Zipp and Enve will have put in to ensure their wheels safe in this super-litigious world, that if used according to ETRTO/manufacturer guidelines, they're any more or less safe than hooked rims.

It's like the disc-brake whinge-fest of a few years back: if you don't like them or don't trust them, don't run them!

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MattieKempy replied to MattieKempy | 2 months ago
3 likes

Now I'm just waiting for Left_Is_For_Losers to wade in with some conspiracy theory that hookless rims are a Socialist plot to take over the world, force everyone to read The Guardian and eat tofu.

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Veganpotter replied to MattieKempy | 2 months ago
2 likes

Leftist here that's pro hookless and vegan

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wickedstealthy replied to MattieKempy | 2 months ago
2 likes

All to you but I won't run tubeless or even hookless as allthe advantage listed are pretty much constructed to push it (except maybe the sealing).
the wheels are tad lighter but that's set off against the far heavier construction or far less thread. The total wheelsystem is heavier with tubeless. I run 56mm wheels 1290gr at pressures around 4.7bar. Rolling resistance with tpu inners are within margin to tubeless. I use hooked wheels as it gives an extra safeguard but that won't exclude all risks. Most tubeless tires are far less puncture proof then tube tires so the sealing is not that of an issue. I run 18k km a year and flat once a year on average. 
So all those so called advantages are actually mostly disadvantages.
The comparison with discs is a moot point as they are safer for normal cyclist

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FreddyFreddrikson | 2 months ago
2 likes

People saying that hookless rims are safe because they've never had an issue is like saying that I don't believe in car accidents because they've never been in one themselves. 
 

I find it concerning Zipp claiming price and performance and weight as sales arguments but not mentioning that those wheels are safe to ride (I guess it hast to do with legal liability) but not having my wheel explode below me is kind of important to me  10

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Veganpotter replied to FreddyFreddrikson | 2 months ago
0 likes

Zipp most definitely lowered their retail prices upon going hookless. That said, old hooked wheels and tires had terrible tolerances. To the point of occasionally needing 2 layers of cotton tape, to breaking beads with very thin tape. Hookless tolerances are outstanding compared to what hooked wheels were in triple the time

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yupiteru | 2 months ago
3 likes

We had hookless rims in the 70's and they were a death trap when the higher pressure tyres started to appear on the market to compete with tubulars used by the racing crowd.

The Mavic Module E hooked rim paired with Michelin Elan tyres was a game changer and changed cycling in a big way.

Now we have gone backwards with hookless rims appearing again.  Why?  Just to save manufacturing costs, simple as that. As if they do not make enough money as it is.

Do not indulge these irresponsible companies and DO NOT use hookless on the road if you value your face. 

Off road is OK, but please learn from us old farts, you will thank us in the end believe me.

 

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Matthew Acton-Varian replied to yupiteru | 2 months ago
0 likes

Modern hookless is designed to take advantage of the now known "faster " approach of having wider tyres at lower pressures run tubeless. They are also manufactured to strict tolerances as dictated by the ETRTO before being allowed to be sold to the public. Something not so strictly adhered to on old steel rims. We are judging a technology based off limited feedback and outlying incidents. If there were more incidents to work from for how many products are in use, then it is absolutely something that needs addressing.

I have seen other articles on the matter which have shown the rim in question - the rim is fully split along its depth. I doubt any wheel of any tyre interface would have stood up to that impact.

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Backladder replied to Matthew Acton-Varian | 2 months ago
2 likes

Matthew Acton-Varian wrote:

Modern hookless is designed to take advantage of the now known "faster " approach of having wider tyres at lower pressures run tubeless. 

I didn't realise you couldn't run lower pressures on hooked rims, I'll have to nip out and put a bit more air in my tyres!

I always thought modern hoolkess is to allow manufacturers to reduce production costs by more than they reduce the sale price.[/cynical]

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Matthew Acton-Varian replied to Backladder | 2 months ago
0 likes

Nowhere did I specifically say you couldn't run lower pressures on hooked rims. Your cynicism is flagulating and utterly confusing right now.

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Simon E replied to yupiteru | 2 months ago
1 like

yupiteru wrote:

we have gone backwards with hookless rims appearing again.  Why?  Just to save manufacturing costs, simple as that. As if they do not make enough money as it is.

This does seem to be a large part of it. I heard that Hambini recently posted a video with cross-sections of rims comparing how little material there is on a modern hookless rim compared to a hooked one.

Like carbon spokes and, to a lesser extent, things like cables/hoses through the headset, these things seem to be sold as "new!", "shiny!" and not really any better. The one thing that changes is that you have to pay a mechanic to work on them due to the complexity and/or fragility of the parts. And it will most likely require a dedicated tool that you wouldn't normally own and can't be used for anything else.

And while I'm not saying people with the money shouldn't buy what they want, I can't help wondering where all these proprietary parts will be after the 'massacre of the SKUs' by Trek (and others will surely follow suit). People buying a secondhand bike will be stuck with parts that can't be replaced like-for-like while the fragility of ~700g carbon frames means that it could be all to easy to put a hole in a top tube or crush a seat stay with a casual knock or fall.

That last option is one of the reasons I don't want to see the UCI's 6.8 kg weight limit reduced. If we try to shave even more weight off a bike just so people can ride up hills 0.1 km/h faster (or simply brag about their bike's weight) they will have shorter lifespan before being dumped in landfill and will be more vulnerable to catastrophic failure.

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don simon fbpe replied to Simon E | 2 months ago
0 likes

Simon E wrote:

yupiteru wrote:

we have gone backwards with hookless rims appearing again.  Why?  Just to save manufacturing costs, simple as that. As if they do not make enough money as it is.

This does seem to be a large part of it. I heard that Hambini recently posted a video with cross-sections of rims comparing how little material there is on a modern hookless rim compared to a hooked one.

Like carbon spokes and, to a lesser extent, things like cables/hoses through the headset, these things seem to be sold as "new!", "shiny!" and not really any better. The one thing that changes is that you have to pay a mechanic to work on them due to the complexity and/or fragility of the parts. And it will most likely require a dedicated tool that you wouldn't normally own and can't be used for anything else.

And while I'm not saying people with the money shouldn't buy what they want, I can't help wondering where all these proprietary parts will be after the 'massacre of the SKUs' by Trek (and others will surely follow suit). People buying a secondhand bike will be stuck with parts that can't be replaced like-for-like while the fragility of ~700g carbon frames means that it could be all to easy to put a hole in a top tube or crush a seat stay with a casual knock or fall.

That last option is one of the reasons I don't want to see the UCI's 6.8 kg weight limit reduced. If we try to shave even more weight off a bike just so people can ride up hills 0.1 km/h faster (or simply brag about their bike's weight) they will have shorter lifespan before being dumped in landfill and will be more vulnerable to catastrophic failure.

Given that competition is high and imagination is low, marketing and sales folks have decided that price is the best way to sell product, us, as consumers, are also driving this race to the bottom. Manufacturers have to make money somewhere and if it doesn't come from the bike, it'll have to come from somewhere else.

 

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wtjs replied to Simon E | 2 months ago
2 likes

 I can't help wondering where all these proprietary parts will be

Just wait for the bike carnage over motors/ batteries/ reglators/ screens/ etc for e-bikes! I have watched videos from bike mechanics and reviewers visiting the latest far East tech shows which are largely about e-bikes just for the schadenfreude of hearing about a failed 2020 Bosch motor (on a bike which looks hardly used) which is going to cost £700+ to replace and the multiplicity of down tube fitments for batteries and motors from increasing numbers of Chinese companies where you're never going to be able to obtain replacements. My 'most useful bike ever' battered Vitus Substance cost £650 in October 2019, and is going to be bashing over rough trails pulling a trailer for a long time to come, unless drivers and Lancashire Constabulary succeed in conspiring to eliminate me.

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Veganpotter replied to yupiteru | 2 months ago
0 likes

Hookless has been around since before 1900. Hookless tubeless is also very far ahead of where hooked clinchers were in the same period from introduction

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maxdabrit | 2 months ago
1 like

It's a shame there is no neutral examination other than Zipp , who it benefits to say it wasn't their manufacturing fault. Watching the race live and subsequent replays- The crash didn't appear to be as catastrophic as is now being touted. I haven't seen anything from the rider saying ' my bad-I hit a rock' .Hence the speculation and concern.

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don simon fbpe | 2 months ago
7 likes

I shall exercise my right never to buy hookless rims as I am not convinced, but thanks for the info Zipp.

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rct | 2 months ago
3 likes

Would it have happened so catastrophically with a properly glued on tub and sprint rim?

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Matthew Acton-Varian replied to rct | 2 months ago
1 like

Wht hasn't been included in this article is an image of the rim completely cracked that was released by Zipp upon receipt of the wheel.

I don't think many carbon rims of any tyre interface would have survived the impact in question.

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dc9876 replied to Matthew Acton-Varian | 2 months ago
3 likes

Couldn't agree more. I've been running the 303 hookless since they came out without any issue at all running as per their specified tyre width / pressure recommendations.

Lets not forget many of the other teams are running hookless rims from other manufacturers without issue too.

It all feels a little bit like the disc rotor debacle all over again.

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Matthew Acton-Varian replied to dc9876 | 2 months ago
2 likes

As I can't afford the latest tech, I am still stuck on rim brakes so the technology is not familiar to me. But all road rims are subject to the same safety tests (including destructive impact tests), and considering the whole cross-section of rim was destroyed at the impact site, the force of the impact that destroyed De Ghent's wheel was significant enough to exceed those tests. Because of this, it is fair to assume that any tyre/rim combination would have suffered a similar structural failure at impact. A tubular might partially hold its shape more as the glued carcass of the tyre stays mostly in place, but the carbon structure of the rim would still be destroyed. I suspect an alloy rim would have a terminal dent in it, too.

Actual disc rotor injuries were one in a million freak chances too. There have been odd reports of injuries when millions of miles, and dozens of races (from pro to amateur local races) happen almost daily. the phrase "mountain out of a molehill" springs to mind.

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Fluffed replied to dc9876 | 2 months ago
3 likes

Not the same. Disc brakes offer better braking, if it's required is another issue, hookless offers no consumer benefits at all. Also, the existing technology, hooked, will not fail catastrophically given slight overpressure or tyre undersize. Good luck to hookless users, you'll need it.

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Thelma Viaduct replied to dc9876 | 2 months ago
0 likes

Exactly, roadies love to make the simple so very complicated, then whine.

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OnYerBike replied to Matthew Acton-Varian | 2 months ago
1 like

It's not just about surviving the impact; it's about the consequence following a rim failure. 

For example, consider the scenes at Paris-Roubaix a couple of years ago: https://road.cc/content/tech-news/two-carbon-shimano-wheels-fold-half-pa...

In both cases, the wheels are horrifically mangled, yet (as far as I can tell from the slightly sub-par videos), the tubular tyres remain attached to the rim.

Obviously I'm not arguing that a wheel folded in half is better than a tyre coming off the rim - those particular incidents could easily have led to a serious crash. But I am saying that it's quite plausible that there are modes of failure where the tyre staying attached to the rim (even if fully deflated) would allow you to roll safely to a controlled stop, while the tyre blowing off the rim will almost always lead to a sudden and potentially dangerous uncontrolled stop.

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webbierwrex replied to OnYerBike | 2 months ago
2 likes

But tubular has it's fair share of crash-causing incidents. Didn't Beloki's career ending crash happen from rolling a tub? Pretty sure Armstrong had a crash too. These aren't incidents of slapdash mechanics either, it's just a limitation of that technology. I'd on average hookless is safer than tubular. I've ridden both and I know feel far safer on hookless.

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choddo replied to webbierwrex | 2 months ago
0 likes

What about hooked tubeless?

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wycombewheeler replied to choddo | 2 months ago
1 like

choddo wrote:

What about hooked tubeless?

the pinnacle of design IMO, much less likely to get a leak between the tyre and rim

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Welsh-Rider 531 replied to choddo | 2 months ago
0 likes

Campag have mini hooked rims for that very reason. Does anyone know what he hit, a rock or a pot hole?  how come no one else hit it, maybe the cause was something else, rim or tyre failure.

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OnYerBike replied to webbierwrex | 2 months ago
0 likes

Sure, tubulars aren't perfect either. But that doesn't mean we shouldn't still advocate the safest option (based on evidence, rather than feelings). And there's also the option of hooked tubeless in the mix.

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Matthew Acton-Varian replied to OnYerBike | 2 months ago
1 like

Firstly - those Shimano failures are on the rear. It is much easier to balance and stop when your back wheel disintegrates - almost impossible for the front as what the case for De Gendt. Just watch fixie riders tring the longest skid - it's the same skill to control the bike just different circumstances. Had the failures been on the front, I can guarantee those riders would have crashed in the same way De Gendt did. The wheel would jam in the forks and instantly stop turning, regardless of whether the tyre was still attached to the rim or not.

Secondly - a deflating tyre is different from a pretzelled rim. Tyre blowouts are rare and in a latex tubular happen instantaneously too. Any deflated tyre type has the ability to "roll off" the rim (even glued on tubs) and I wouldn't expect an ETRTO approved hookless system to be significantly easier to roll off than a tyre on a hooked rim.

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