Zipp releases photos debunking hookless rim failure after De Gendt crash

The biggest headlines of the past few weeks have all surrounded the dramatic pictures of Thomas De Gendt's bike propped against a barrier at the UAE Tour. There is sealant splashed across the front wheel, the Vittoria tyre off the rim, and a tyre insert exposed and jammed between the wheel and the fork. So far the only thread that connected all those headlines is that no one knew for sure what happened. 

Since the crash, De Gendt, Zipp, and Vittoria have all confirmed in separate statements that an impact was at fault. Each has referenced an errant rock as the guilty party but, so far, there's been no evidence. Today, that changes.

After in-house analysis, Zipp has shared images with Cyclingnews, showing the wheel in question dramatically damaged with a sizeable crack across the tyre bed. 

Upon seeing these images, our thoughts returned to the aforementioned shots of De Gendt's bike. Despite all the furor and ongoing debate, there was very little discussion of a damaged rim. Surely a crack of this size would have been noticeable? 

Indeed, it was. With a bit basic photoshop brightening adjustment applied to the high res images, it's clear that the same crack was there, and easy to spot, all along. This aligns with with what Zipp engineers found during investigation and subsequent statement that "The engineers have reviewed the wheel in question and it was clearly a result of a significant impact. When you hit something hard enough to destroy the structure of a rim, the tyre is going to come off." 

This is a sentiment shared by Jake Pantone, VP of Product and Brand for Zipp's competitor, Enve Composites. He told Cyclingnews "broken wheels can’t be expected to retain a tyre. Tubes, tubeless with hooks, tubeless without hooks, and tubulars will all throw the tyre if the rim is no longer load bearing or breaks through the dimensionally critical tyre bed." This also matches with numerous other examples, such as Annemiek Van Vleuten's freak World Championships crash.

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Typically, damage of this severity marks the end of the discussion but in this case it didn't. The absence of any obvious damage to De Gendt's rim in this case – or at least, the absence of anyone brightening the image in Photoshop to find it – allowed the conversation to turn to hookless rim and tyre compatibility. Escape Collective posted an in-depth 'warning to all', and highlighted the ETRTO compliance of the rim and tyre combination as a potential factor in the equipment failure.

While the latest information shows the combination was not related to this incident, is there still a discussion? Lotto Dstny's choice of a Zipp 353 NSW wheel (with its 25mm internal rim bed) and a 28mm Vittoria tyre is not a recommended choice by the ETRTO and that leaves a question. De Gendt's team mechanics claimed they were "100% within the rules" but what about consumers?

The ETRTO (European Tyre and Rim Technical Organisation) guidelines are just that: guidelines. There are no penalties for ignoring them. It's unclear what rules the Lotto-Dstny mechanics were referring to, but the only actual rules that govern rim and tyre compatibility come from the ISO (International Organization for Standardization). Its standard mandates that wheel and tyre combinations should be able to maintain 110% of the maximum tyre pressure for a time of five minutes. As Felix Schäfermeier of Schwalbe says, it's "easy to pass." 

This is a rule that CPA president Adam Hansen has been critical of, and the UCI has since announced it will "study the [wider hookless] situation with a matter of urgency."

Reassuringly, the wheel and tyre brands we've spoken to all agree, and are already testing well in excess of this for longer periods.