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

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. 

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 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.