What are hookless rims and do you need them?

From: Cyclingweekly

They’re hardly universal yet, but the top road wheel brands including Roval, Enve, Zipp, Corima and and Giant/Cadex are all getting behind the 'new' hookless tech. But are they really better than the traditional hooked type? More importantly - are they safe? And should you be riding them?

“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.”

The key to the better performance is 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.”

Hookless also reportedly has an aerodynamic benefit, as Donzé explains: “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.”

hookless rims are made using a simpler but superior manufacturing process, says Donzé, which results in better compaction of the carbon, better resin distribution through the rim, tighter tolerances in the tyre bead seat, less waste and less scrap.

“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. 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."

And finally, thanks to the better resin distribution achieved by the hard steel tool, a hookless rim saves a considerable amount of weight over a traditional hooked rim with no strength penalty: “We were able to save 300g with the 303 Firecrest,” says Donzé, “and it’s just as strong in terms of impact.”