Damaged rim caused Kern Pharma rider's freak tyre blowout, says team

A damaged rim was the cause of the freak tyre blowout that led Marc Brustenga to crash in the bunch sprint on stage two of Étoile de Bessèges, according to the rider's team, Kern Pharma.

Brustenga lost control of his bike, veered sharply across the road, and crashed into the safety barriers in the closing moments of Thursday's stage.

Video footage showed he made no prior contact with other riders, and was instead the victim of a freak rear tyre blowout. He finished the stage on foot, carrying his bike across the line with its rear tyre completely unseated from the rim.

Since his Kern Pharma team use hookless rims supplied by brand CADEX, some questioned if the mishap was caused by an issue between the rim and tubeless tyres.

A team spokesperson told Cycling Weekly on Friday a "thorough investigation" has now been conducted into the incident.

"A few hundred meters before the puncture, Brustenga entered a roundabout and hit a hole, which slightly damaged the CADEX rim due to the speed," the Kern Pharma statement read.

"However, he felt that he could continue riding, and he did. The tire only came off the rim when the rim could no longer support it due to the previous crash.

"Brustenga was using CADEX 50 Ultra Disc wheels, which we've been using for the last three seasons with an outstanding performance.

"Finally, and most important, Marc did not suffer any significant injury during the incident."

The incident was reminiscent of one involving Thomas de Gendt at last year's UAE Tour. Also riding hookless rims, the Belgian too suffered a tyre blowout and crashed. The cause was later attributed to the wheel having been damaged earlier in the stage.

"Zipp has the wheel to investigate, they did this, and their investigation said it was because of a rock or something on the road," De Gendt said at the time. "After the stage I saw the damage and it was not just damage from hitting the road, it was really damaged from hitting something."

The De Gendt incident, nonetheless, spurred the UCI to launch an investigation into the use of hookless rims with tubeless tyres. The governing body went on to remind teams to follow compliance regulations set out by the International Organisation of Standardisation (ISO).

"These standards provide a framework for the compatibility of tyre and rim widths on bicycles," the UCI said.

"The UCI notes that the norms defined in these ISO standards have not always been respected and does not rule out the possibility that this may have been a contributing factor in some of the incidents encountered."