Zipp 404 Firecrest carbon clincher road wheelset review

Having proved with the 303 that a wider rim can handle side-to-side flex better and improve the way a tyre 'gives', Zipp have used a wider rim for their 404 Firecrest. Fitting a tyre to the wide rim lowers its profile, creating a wider base and more pronounced curve between the contact patch and sidewalls.

Zipp claim that the new shape not only improves airflow at the front of the wheel but also deals with the turbulent air at its trailing edge more efficiently than ever. The result is also more confident transition when you're leaning into corners; we felt happier leaning the bike over, giving faster entry and exit speeds and helping us maintain pace through twisty stuff.

The company's previous toroidal shape rim – which 'bulged' out from the braking track before narrowing – was among the best available and the new Firecrest easily feels its equal. Where it's much better, though, is in crosswinds. You can still feel the effect of wind hitting from the side, as you would with any 58mm deep rim, but what's impressive is 'how' you feel it. It's more akin to a steady, low pressure push rather than a jolt.

A good pair of aero wheels will make you feel faster and allow you to hold higher speeds for longer with less effort, and the 404s are the most impressive aero clinchers we've ever tested. We've seen our loop times bettered consistently over the past three months with these quality hoops. They also excel in the comfort stakes. Deep-section carbon rims can be stiff and a little harsh – not so the 404s. They feel more like shallow-depth aluminium wheels than hard-riding aero hoops.

Carbon braking surfaces can build up heat alarmingly quickly, leading to grabby braking and a lack of feel, but the 404s have a highly heat resistant resin coating that leads to consistently good braking. In fact, they're only bettered by Easton's ThermaTec brake tracks when combined with SwissStop's Yellow King carbon pads. There's a dedicated Platinum SwissStop pad for Zipp that gives a much better feel while maintaining power, and is the best choice for the 404s.

At 1,640g a pair, including skewers, the 404s are among the lightest available for this rim depth. The rim itself is lighter than on the competition too, so the wheels also have admirable climbing abilities. They're heavier than a dedicated lightweight climbing wheelset but the gains on descents more than make up for it.

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