Challenge issues consumer product safety bulletin

Challenge has issued a safety bulletin to its customers, to reconfirm that its tyres should not be used with any rims or wheels that do not comply with either the current 2019 ETRTO, past ETRTO or soon to be released ISO 5775 global standards for tyre and wheel fit.

It specifically clarifies that both old and new ETRTO and future ISO standards require a minimum 0.7mm rounded radius on all hooked rims.

The bulletin said: “It has come to Challenge’s attention that ENVE SES model carbon wheels do not comply with the above standards on the design of the rounded hooked rim radius. In fact, ENVE’s SES have two sharp (<0.2mm) radii in their hooks, that leave two parallel cuts about 0.5mm apart, around the entire radius of our (and other company’s) tyres, at around 3-4mm above the bead.

“Challenge has noted failures of its clincher tyres, communicated by consumers and athletes, caused by the sharp edges on the ENVE SES hooks. This international design standard violation has been communicated back to the affected consumers, shops, endorsed teams, ENVE and its parent company, as Challenge has been made aware of problems. ENVE, however, continues to produce and promote usage of the said SES models, as part of its line.

“Challenge has consequently been forced to list the specific ENVE SES rims as not compatible with any Challenge clincher tyre models, on the website. Challenge asks that consumers do not mount ENVE SES wheels with any model of Challenge clincher tyre whatsoever.

“Failure to follow this warning could cause the ENVE SES wheel to cut Challenge’s quality casings resulting in explosive air loss from the tyre and/or inner tube, potentially causing a crash and injury to the rider.”

It added that bulletin is also aiming to provide the technical clarification that only a ‘precisely defined’ 622.0mm+-0.5mm bead seat diameter, specifically defined wall height and centre channel, as described in the new above standards, will safely and easily allow proper tyre and rim fit and function.

Challenge said it has regularly been attending standards meetings and has been involved for the past three years in confronting the market’s accelerated changes, such as the implementation of progressively wider rims, carbon fiber clinchers rims and tubeless and tubeless ready tyre technologies. It added that it has invested time, knowledge and energy together with other elite bicycle industry companies to address and update tyre and wheel fit issues with the ETRTO and ISO.

Challenge handmade tyres have been produced for close to 20 years using the same handmade processes that have been “proven over the past 50 years at the highest levels of racing without significant failures – if the rims and wheels comply with internationally accepted design standards”. This also applies for both aluminium and carbon fiber rims.

Challenge added: “Regarding carbon fiber rims, there had also been other periodic problems in the past with some carbon rims that had cut our (and other tyre manufacturers’) tyre casings just above the beads. These tyre cuts were however normally caused by less than optimal QC at the factory, resulting in quality issues of improper finishing at the tyre hook during production. Normally roughness at the hook was due to failure to completely remove resin flashings created while molding the rim.

“Proper finishing leaves the required 0.7mm minimum radiused rim hook smooth, without roughness, thus eliminating a potential tyre failure. In the above cases, Challenge has routinely and successfully worked with the wheel suppliers (including ENVE) to fix the problems or replace these wheels to the consumer. However, specifically with ENVE’s SES model wheels, it is the first time that Challenge has known of a rim hook design that does not meet the above recognised design criteria, reason for which Challenge feels compelled to follow up with the release of this informative bulletin to protect its customers.”

For further questions contact Challenge at

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