During the 1970's, tubular rims were the best choice for racing. A tubular tyre is basically glued on. There were also the presence of wire-on tyres which had a wire bead. However, wire-on tyres were heavy and slow.
In the later part of 1970's Mavic introduced Module E rim which revolutionised the racing world. It had a hook shape which helped in making the tyres lighter. The bead was foldable and prevented it from bursting at high pressure.
The top road wheel brands including Roval, Enve, Zipp, Corima and Cadex are all getting behind the ‘new’ hookless tech.
“There are a number of misconceptions about hookless rims,” says Bastien Donzé, Zipp wheel product manager. “First is that hooks on the rim are necessary to ensure safe retention of the tyre. Our testing shows that tyre burst pressure or tyre blow-off is very similar on hookless rims to hooked rims.”
Zipp recently launched a new 303 S and 303 Firecrest, both of which use hookless rims However, the maximum recommended pressure is just 72psi “It’s not because 72psi is the limit of the wheel but that’s because that’s what’s imposed by regulations like ISO and ETRTO [European Tyre and Rim Technical Organisation],” Donzé explains.
He added that the sidewalls are spaced further apart in a hookless rim and supported better since the bead is not pulled inwards by the hook. “A big tyre on a traditional rim will be like a lightbulb in profile. With hookless the tyre sidewalls are being supported a lot better. You get the full the benefits of a big tyre and low pressure without any of the squirm or the rolling resistance.”
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According to Donze, hookless has an aerodynamic benefit- “Because the tyre is not pinched, you have a much cleaner transition between the rim and the tyre. Even though the rim is wider and increases frontal area, the system with the tyre is quite a bit faster.”
“For carbon rims with a hook you have to design a soft mandrel made of silicone that can squeeze into the hooks and mould the tyre bed cavity. Using a soft mandrel you’re losing manufacturing accuracy and generally you end up putting in more material."
He further stated - "When you go to hookless you can replace that silicone mandrel with a steel one that gives better accuracy [so a better interface with the tyre] thanks to better compaction of the resin that also results in more strength on the wings of the rim. The silicone mandrel is one time usage – it has to be thrown away after every use, so that’s a lot of waste. The steel one lasts thousands of cycles. There’s a reduction of the costs, which equals a lower price for the end-user, as demonstrated by the new price of our 303 wheels.”
Dov Tate, founder of British wheel brand Parcours said that, "the big issue hookless has at the minute is with pressure ratings.
He added, "With big off-road tyres you’re never going to be at the sort of pressure where you’re running the risk of blowing off. But on the road, all the pressure recommendations on new hookless road wheels are really low, 72psi is the recommended limit for a hookless tyre.
“If you get the right tyre and rim you’re fine,” says Tate. “The problem is that because hookless technology and even tubeless tech doesn’t have clearly defined standards, there are too many variables to be able to guarantee that every tubeless tyre will be able to fit on every tubeless rim above 72psi and that’s why ETRTO haven’t signed off on it yet.”
