UCI to Perform ‘Urgent’ Study of Hookless Rims & Tubeless Tires to Address Safety Concerns

Written by Zach Overholt Mar 01, 2024 8:46 p.m. ET

Zipp 353 NSW tubeless wheels, ultra-wide 25mm internal hookless tubeless carbon disc brake road bike wheelset, rim detail

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Recently at the UAE Tour, Lotto Dstny rider Thomas De Gendt hit the deck. But unlike many run-of-the-mill crashes in pro cycling, De Gendt’s crash ignited a firestorm of media attention due to the cause. Well, due to the potential cause as no one can say for certain what caused the crash, but we do know that De Gendt was riding hookless rims and tubeless tires with a tire insert.

During the crash, the tire nearly came off the rim completely leaving the Vittoria tire liner flapping in the breeze. Since then there have been many questioning the compatibility of certain tires and hookless rims, including the Cyclistes Professionnels Associés whose president, Adam Hansen, has voiced the CPA’s concern over hookless rims in the Peloton.

As a refresher, hookless rims eliminate the small hook on the rim which in the past has served to lock the tire bead in place. Hookless rims instead rely on the shape of tubeless tire beads to hold the tire in place with friction against a straight side wall. The advantage is supposedly a lighter rim with a reduced chance of pinch flats and impact damage to the rim while allowing the tire to fill out a more rounded profile and run lower pressures for better grip.

From a manufacturing standpoint, hookless rims seem to be easier and less costly to manufacture, which hypothetically results in a more affordable product.

However, hookless rims have specific requirements for tire type, size, and pressure – with most hookless rims required to run below 72.5 PSI.

UCI Weighs In

If you’ve been following the drama, you knew this part was coming: the UCI is now investigating. Releasing a short statement today, it is clear that the UCI intends to quickly decide whether hookless rims have a place in the pro peloton.

In light of a series of recent incidents involving the use of hookless rims and tubeless tyres (a combination commonly referred to as hookless) in professional road cycling, the Union Cycliste Internationale (UCI) has decided to study the situation as a matter of urgency with a view to taking a rapid decision in the interest of rider safety.

These measures will be communicated as soon as possible.

The UCI shall continue to work closely with the stakeholders of cycling and equipment manufacturers to ensure that appropriate measures are taken both in the short and long term. This review and the decisions that will follow are part of the UCI’s policy to promote rider safety, one of its major concerns.
-UCI

Zach Overholt

5,633 articles

Zach Overholt is the Editor in Chief of Bikerumor. He has been writing about what’s new in the bicycle world for 12+ years. Prior to that, Zach spent many years in the back of a bicycle shop building and repairing nearly every type of bike, while figuring out how to (occasionally) ride them.

Based in Ohio, Zach is now slowly introducing a new generation to cycling and still trying to figure out how to fit the most rides into a busy schedule as a new dad.

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56 Comments

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c c

1 month ago

Hookless is a risk bigger than disc brake with virtually no benefits to riders. If certain riding positions, which caused no crash at all, are banned, why not hookless?

JoeS

1 month ago

Reply to c c

Yep, for road cycling and most gravel riding it is a moron’s solution desperately looking for a problem to solve. Makes some sense in MTB and gravel where you are truly encountering regular terrain that provides a large probability of a pinch flat. For most road and gravel riding it’s a dangerous solution to a virtually non existent problem, and it limits your psi choices and tire choices. I run 100% hooked rims on my road and gravel bikes and have zero plans of buying any hookless rim wheelsets for either of those disciplines going forward. Consumers do stupid shit all the time, follow trends and are in general gullible marks for marketing departments. Running hookless on a road or gravel bike is the ultimate example of that, and in particular on a road bike is as stupid as it gets.

Tim

1 month ago

Reply to c c

Why is disc brake a risk?

Dave R.

1 month ago

Reply to Tim

Back when disc brakes in the pro peleton was being debated, the concern was that disc rotors would be a slicing sharp edge in case of a crash. A couple of riders did sustain injuries like this, but Sramano and carbon wheel manufacturers prevailed. The UCI does require rotor edges to be radiused and blunted for approval now.

-2

c c

1 month ago

Reply to Tim

I don’t think it’s too big a risk but it’s what the racers said when UCI / the industry tried to introduce disc brake to road race. If we follow their logic, racers should voice out against hookless stronger than the disc brake case.

Yeah sure

1 month ago

Reply to Tim

There were two primary arguments with regards to disc brakes in the pro peloton.

1.) the discs would be a laceration or burn risk in a pile up crash. (This to me was dubious since bicycles have many pointy disks already on them (chainrings and cassettes) and didn’t think that the burn risk was an issue in other disciplines.

2.) Having two different braking types for riders would cause an issue. This was fruitless to me because some wheels already brake way better than others. And pros know how to deal with that. Personal anecdote. I’m phenomenal on the brakes riding motorcycles and rely on outbraking people to make most passes on track days. I’ve still yet to have someone on a liter bike with no braking skills run into the back of me. I’d wager that gap is much larger than pro cyclists on rim/disc brakes.

Always thought the slow roll out for disc brakes was a combo of old European guys not liking change and also to allow the smaller brands to go road disc (I know rim brakes are occasionally used) since a 50/50 peloton just seems like a nightmare from a neutral support perspective. Personally for road I prefer rim brakes for road but the arguments against them for racing where kind of dumb.

Ves

1 month ago

Reply to Tim

It’s useless for road racing. That’s why.

-16

Ed LLorca

1 month ago

This whole frackas is based around ZERO benefit to the rider. The benefits are all for the manufacturers as they still try to sell us wheelsets for what you can buy bikes for and wholes bikes that cost as much as cars. I will never ride hookless.

JoeS

1 month ago

Reply to Ed LLorca

Yep, particularly for road bikes and most gravel bikes the whole hookless rim and tubeless tire trend is a massive BS loaded marketing scam to sell gullible easily marketed to clowns on the notion they now must change out all their wheelsets and tires & tubes for hookless rim wheelsets and tubeless tires. Complete laughable BS. Hookless rims and tubeless tires on road bikes and mist gravel bikes is a laughable solution desperately searching for a meaningful problem to solve. It’s a clown show.

Large D

1 month ago

Reply to JoeS

Gravel tires are run at way lower pressure than road, while I’m not using hookless on my gravel bike currently I don’t worry about it there (I have hadhookless wheels in the past). I weigh 135 lbs and ride my gravel tires all well under 30 psi.

Large D

1 month ago

Reply to Large D

“have had hookless in the past”

-5

Robin

1 month ago

Vittoria put out a statement that said that the tire came off because the rim broke after De Gendt hit a rock or summat.

Hookless per se isn’t the problem. The problem is the current standards and adherence to standards. Not enough attention is being paid to safety margins/tolerances. Then there’s the poor communication by all involved regarding what the actual standards say. For example, the oft-quoted max pressure for hookless rims is 72.5 psi, but what the standards actually say is that the max pressure for 25-29 mm hookless tires is 72 psi. If you use 30-34mm, the max pressure is 65 psi.

The solution is likely thicker/stiffer rim side walls; tighter tolerances for tire and rim manufacturers; bigger safety margins; and better communication about appropriate tire pressures to the public.

Here we go again

1 month ago

Reply to Robin

I’m inclined to think you’re right and tolerances and specs are critical, more so than hooks or not. Then I remember what a mess BB30 was for so many brands or how many carbon parts get recalled because of poor QC or the parts fitted to them.
The bike industry has pro racing driving marketing and low costs driving manufacturing and purchasing decisions. It goes wrong too often.

Eggs Benedict

1 month ago

Reply to Robin

Or just ride hooked rims.

The only reason the rim industry is pushing hookless is because it’s easier to manufacture rims without the hook.

By increasing the rim wall thickness you’ve just eliminated any weight saving benefit, and increased the cost of the rim. By making the tolerances tighter you’ve just increased manufacturing costs for both the rim and tire.

There is absolutely no benefit to using hookless rims on a road bike and most gravel scenarios, as stated by a previous commenter.

Robin

1 month ago

Reply to Eggs Benedict

I didn’t say otherwise. I merely mentioned contributing factors to the issues with tubeless. With that said, there’s no reason that it shouldn’t work, and I don’t think it’s going away.

I don’t ride hookless, but it seems a pretty pointless discussion if objectivity is rejected.

Billyshoo

1 month ago

Reply to Robin

We might make them go away. If no one buys them, they’ll definitely go away.

tst4nic

1 month ago

Reply to Billyshoo

Well you can’t buy giant tcr complete bike without hookless rims

Matt

1 month ago

Reply to tst4nic

Then maybe you shouldn’t buy that bike? It’s possible there may be other makes and models available for purchase.

Yeah sure

1 month ago

Reply to Eggs Benedict

Yeah I don’t get it. It seems like to get hookless to work the onus is put on the customer to run reduced pressures and even then then I think you’re way to dependent on bicycle industry tolerances for a safety. From what I can tell a lot of the safety on a hookless setup comes from the tightness of bead/bead seat interface and the strength of the sidewall which is totally fine on a car or motorcycle tire but you really can’t make the beads too tight on a bicycle because you’ve got to be able to stick a tube in there during an emergency on the road. And unlike ADV riders most cyclists aren’t carrying multiple long steel tire spoons and are able to use the side stand with a 500 lb bike to push the bead into the valley.

Seems like hooked rims are the real innovation since they allow you to safely run high pressure bicycle tires yet make installing and removing the beads easier. They should’ve just charged an extra $1000 and developed some new name for hooked rims. The gullible will still buy it.

Kool Stop Tyre Lever Sales Dept.

1 month ago

Reply to Yeah sure

Ezy-Loc Tires, no messy latex, just use our handy inflatable tire bladders.

Astro_Kraken

1 month ago

Reply to Eggs Benedict

By increasing the thickness you may have increased the strength of the rim, but you’d never know because it has a tire on it.

Silidons

1 month ago

Reply to Robin

So hookless rims are so unsafe that being at the max PSI, or 5% over, which would be ~76 PSI, would cause a catastrophic failure? You’re okay with that?

I was reading the description on a set of Zipp wheels. Literally from Zipp:

“Wide hookless rims create a seamless transition to the tyre, reducing drag.”

What a stupid advertisement. But people are dumb and will believe anything.

-1

David Lewis

1 month ago

Reply to Robin

It’s worth looking at Ronan McLaughlin’s analysis of the accident on Escape Collective. The ISO standards for tire/rim compatibility say that the 28mm tire he was running should have been on a rim with a maximum internal width of 23 mm, and ideally probably 21 mm to allow for some margin. It was in fact on a rim with a 25 mm internal width, thus reducing the blow-off pressure. There was nothing wrong per se with either tire or rim, but they were not compatible. Ideally, the Vittoria rep who supplied the tires should have asked what rims they were running on, and somebody on the team’s crew should have known about that spec.

Lactic Flaccid

1 month ago

Reply to Robin

Jan Heine wrote something similar: https://www.renehersecycles.com/uae-tour-and-tubeless-what-is-safe/

PStu

1 month ago

If you use the Silca tire pressure calculator, you can quickly get a recommendation beyond the 72.5 psi limit. I’m using latex or TPU tubes on my road bikes with hooked rims. Low rolling resistance, minimal maintenance, replaceable roadside, and even with a big gash, a tire boot and a new tube can have you rolling.

Dave R.

1 month ago

Reply to PStu

From what I’ve seen, pulling off one side of a tubeless road tire on the side of the road to put in a tube and pop the tire back on sounds like a hell of a struggle to be doing with traffic whizzing by, plus road psi is higher so tubeless sealant gets blown all over the bike and wheel if there’s a puncture. For training wheelsets, a tube with sealant in it sounds like a good compromise for puncture alleviation, and for race/fast wheels your type setup. Plus clinchers are cheaper and easier to mount initially.

Eggs Benedict

1 month ago

Reply to PStu

I just bought an 8-pack of TPU tubes from AliE, at approximately $5.50 per tube. That’s less than the cost of a butyl tube.

Evan

1 month ago

If they ban, zipp is done.

-6

bielas

1 month ago

Reply to Evan

also ENVE has all hookless rims, and other brands.

But the problem is not hookless, or Zipp. The problem was, and I am surprised nobody mentioned, that Lotto team was using Zipp 353NSW wheels that have 25mm internal hookless rims. These wheels are intended to be used with 28mm, or wider, tires, however the Lotto team was using 25mm tires… so obviously the tire blew off, as it is too narrow for that rim (and that even before knowing what pressure they were using, likely quite high too)

So, any component can fail if it is used r set up wrong

Look at all the other Protour teams and riders, almost every team using hookless-tubeless and no blow offs

DefRyder

1 month ago

Reply to bielas

Agreed. While I understand the controversy of hookless wheels, it seems to me that De Gents’ crash is being sensationalized by media pundits. Tadej Pogacar won the Strada Bianche on Enve hookless wheels (unsure of tire width/pressure used).

And, as you pointed out lots of other pro teams use hookless wheels with little trouble. The attention hookless wheels are garnering now may prove to be beneficial in the long run by forcing manufacturers and customers to be more mindful of the recommendations to use proper set up (tire width, pressure, etc.).

FritzP

1 month ago

Reply to DefRyder

Tadej rode the SES 4.5 at Strade Bianche which are 25mm inner width and Conti GP5000 S TR 28mm tires.

FritzP

1 month ago

Reply to bielas

Are you sure about the 25mm tire width? The Escape Collective article mentioned above said he was running 28mm tires.

Brent

1 month ago

Reply to bielas

No, they used 28mm tires, the debate is the Etrto norm changed and requested to use 29mm tires minimum and Zipp didn’t updated their recomendation saying “we know, test better, 28 works just fine”

brian

1 month ago

Hi Zach, as a structural engineer i have doubts regarding your list of advantages for hookless rims. With regard to the rim being lighter I have not seen any data from any brand to support this fact. Nor is there any data from any Brand with respet to impact damage as you suggest. The bottom line regarding the health and safety of the rider is that a rim manufactured with a hooked bead can still be run tubeless quite successfully irrespective of the brand spin. I totally agree it is cost that drives hookless and this is being driven by profit margins and not engineering that is customer focussed, Thanks

Sevo

1 month ago

Problem is that tubeless for road works only when both tire and rim manufacturers adhere to high tolerances required to pump up a tiny road tire to 130psi. A bad run on either side or a minor ding of the rim is all it takes to compromise….and all for what? A regular high performance clincher with a latex tube is plenty light and easier to deal to change on the side of the road. Or for us pleebs, just get a lightweight butyl tube (more consistent tube thickness) with a removable valve core so you can add a fluid once or two of sealant to it.

Tubeless has worked so well on gravel and mountain bikes because of the lower pressures of each. With either you’re likely running less than 40psi vs road being 3x the pressure. I don’t see road tubeless being a smart move to pursue, tires are harder to put on and not saving enough weight to make it worth while.

-3

FritzP

1 month ago

Lotto had another Vittoria blow off a Zipp NSW front wheel at Strade Bianche. Looks like the 454 which is narrower.

FritzP

1 month ago

Reply to FritzP

In the Escape Collective Strade gallery there’s a photo of the Lotto rider and it clearly looks like the Zipp rim broke.
Gallery: The favourites prevail at a wonderful Strade Bianche – Escape Collective

FritzP

1 month ago

UAE runs hookless Enve wheels with Conti tires. The SES 4.5 is 25mm inner width and the product page on the Enve website says min tire width is 27mm!

I’m wondering if Vittoria or Zipp has sizing tolerance problems.

Also these two blow offs question the claims about foam inserts improving retention.

I’ve been running Zipp 303 Firecrests with 28m Conti GP5000 S TR tires at 61-65 psi (Silca calculator) and been quite happy with them. I’ve done some hard descending and not had any problems.

Tom Jones

1 month ago

I have hookless rims, on my 1973 Schwinn Varsity lol.

There is always snake oil around somewhere.

Brent

1 month ago

Reply to Tom Jones

tires used metal tire beds at the time. hooks came with the use of synthetic tirebeds allowing a massive weight gain and to fold the tires.

Bumscag

1 month ago

Came for the armchair engineers and pretend experts flooding the comment section with anecdotal evidence and absolute nonsense and fear mongering.

Was. Not. Disappointed.

bielas

1 month ago

Reply to Bumscag

thanks, your contribution to this discussion was invaluable. Not.

Not pretending to be an engineer or expert, but simply put I have been using different hookless rims and tubeless tires in the last 5-6 years without any issues, maybe because I follow the minimum width directions and don’t over-inflate the tires (otherwise, what would be the advantage of tubeless in road bikes? from my non-engineering non-expertise). My experience, and many others’ says they work, but there is always somebody breaking stuff no one else breaks and mis-using stuff as it shouldn’t

Bumscag

1 month ago

Reply to bielas

I guess reading comprehension isn’t your strong suit, huh? There aren’t a lot of actual, working engineers or race mechanics bagging on hookless/tubeless.

Just a bunch of trolls afraid of progress…

And you, hilariously misreading my comment.

Brent

1 month ago

Reply to Bumscag

Well, DT / Swissside, Bontrager, Roval, Mavic, Campagnolo, Shimano, Vision do have only road hooked rims and their Engineers are quite clear why.

signed: a mechanical Engineer who discussed with some of the brands above and understand their concerns 🙂 There is zero user gain in having HL rims on the road (MTB can discuss), not lighter, not more aero, no more rolling resistance. As mentionned many times it is an production-innovation allowing to use hard (metallic) molds to form the upper part of the rim, speed up production, reduce production cost, reduce the QC problems and adjust QC protocols accordingly (a more robust production quality allow a more relaxed QC protocol).

Joey C Brown

1 month ago

Reply to Brent

*Industry Nine hooked as well.

Eggs Benedict

1 month ago

Out of curiosity, has anyone who lives area that is subjected to high temperatures (90F+) for weeks on end (somewhere like Arizona or Texas) ever taken the tire pressure before and the pressure at the end of the ride to see if there is a pressure increase in the tire?

Bumscag

1 month ago

Reply to Eggs Benedict

I live in LA and run TireWiz. I’ve seen a 4psi increase on hot days

Yeah sure

1 month ago

Reply to Eggs Benedict

+3-4 psi hot vs cold in 115°

WorkonSunday

1 month ago

Hookless is only problem when you try to put a narrow tyre on. Almost all common cars on the road use hookless rim. Also mtb rarely has any problem. Its only when pressure is 70+psi and tyre width barely few mm wider is causing the problem

Brent

1 month ago

Reply to WorkonSunday

But cars have super thick tire beds not stretching imposing to install them on a machine… we could use metalic tire beds, tires would weight 5/600g and rims would need to be suuuuper strong (and heavy) to support installation.

Yeah sure

1 month ago

Reply to WorkonSunday

Clearly you’ve never installed a car or motorcycle tire.

seraph

1 month ago

I’ve been running hookless rims for gravel between 50 and 60 psi for a few years now. With regular lower pressures they’ve been solid. No issues.

PinkPuffinBicycles

1 month ago

Next time your installing Vittoria Corsa Pro’s you should try a few on the same rim. The darndest thing is that I’ve had some fit very tight and some fit very loose out of the box… Just saying along with the tire width issue there seems to be some ETRO QC issues with the tires.

Ed LLorca

1 month ago

Not that I trust the UCI go against almost every rim manufacturer, but I say GOOD!. Hookless rims and tires to tight to remove on the roadside are a travesty foisted upon us riders and they can’t disappear fast enough.

DVT

1 month ago

Is tubbies still allowed?
Will that not be equally unsafe?

Mike

1 month ago

Hookless rims are one problem, Another is using rims designed for tubeless tires with tires that were designed for tubes. The bead on some of the latter is too small and moves within the hook channel, causing the tire to come off the rim and a crash. Some of the wheel manufacturers claim that any tire can be used with a “2 way” rim. Not so. I have personal experience with a crash as a result of this problem.