Industry divided over new tyre rim-size regulations

Some much needed standardisation for tyre and rim combinations has arrived, but not everyone is happy about it. Hannah Bussey digs a little deeper...

- Hannah Bussey

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.