Some much needed standardisation for tyre and rim combinations has arrived, but not everyone is happy about it. Hannah Bussey digs a little deeper…
Unbeknown to most, a Brussels based organisation called the European Tyre and Rim Technical Organisation, or ETRTO, has been debating the safety of hookless rims and compatible tyres. And their decision could impact your ride.
Made up of experts from wheel and tyre manufacturers, the ETRTO committee is responsible for producing the recommended safety standards on all aspects of vehicle wheel rims and tyres.
ETRTO’s new standard states that there should be a minimum of a 5mm overlap between the internal measurement of a rim and the size of the tyre fitted to it. This means that previously popular combinations of 25mm internal rims and 28mm tyres now sit outside the new guidance.
According to Mavic’s Global PR manager Michel Lethenet, the change “results from a world leading tyre manufacturer, which has demonstrated that a 28mm tyre mounted on a 25mm rim could derail from the rim.”
“The reason why it’s creating such debate is that 28mm tyres on 25mm internal hookless rims are proven to create a really aero profile,” Patrick Blake, lead product and commercial manager at Hunt Bike Wheels tells CW.
“Now ETRTO deems this combination unsafe and recommends fitting at least a 30mm tyre on a 25mm rim instead. All of a sudden these wheels are going to become slower.”
What’s first? The tyre or the rim?
Clearly there are a few unhappy brands out there. Zipp, ENVE and Chris King all have 25mm internal hookless rim options available, and all recommend running 28mm tyres for optimal performance.
An added complication is that some of these brands sit on, or feed into, the ETRTO committee who made the recommendations, meaning that as an organisation it doesn’t appear unified over the change, with infighting a result of brands defending design principles.
Fundamentally the dispute appears to be about whose responsibility it is to ensure that a tyre should stay on a rim: the companies that make the rims, or the ones that make the tyres?
In a formal statement Zipp said: “As participants in the ETRTO standards meetings, we knew the compatibility table would change. We understand the updates, but they contradict our position.
We know there have been enough wheelsets ridden in the past several years with the 28c tyres on 25mm rims to prove that the combination is safe and delivers many proven performance benefits.”
ENVE holds the same position. “This blanket recommendation from ETRTO just doesn’t capture the nuances,” says Jake Pantone, vice president of Product and Brand. “The new guidance also states ‘labelled’ tyre size. Well, all that tells a product ma
