Wider than existing designs, featuring a rounded oblong-ish shape and with a notably rounded inboard leading edge, Zipp’s Firecrest aero rim profile revolutionised thinking on cycle wheel aerodynamics when it appeared last year. The latest model to join the Firecrest range is the 303, which is a reworking of the old 303 model to produce both clincher and tubular wheels with the same external profile, the clincher rim obviously having a rim bed suited to clincher tyres.
At 28.5mm wide and 45mm deep, the rim is a lot smaller than its 404 and 808 siblings. Zipp nevertheless promises exceptional aero performance and stability in cross winds along with the lower weight – 1190g for the tubular pair and 1490g for the clincher – expected of a shallow rim. The surface wears Zipp’s Automated Boundary Layer Control dimples, which, according to Zipp, energise the airflow boundary layer to keep flow attached to more of the rim surface than would be the case without them.
The 26.5mm width of the clincher rim brake track widens the profile of the inflated tyre on it, adding directional stability and improving steering response without compromising on rolling resistance. The tubular rim sidewalls are designed to deflect under load to add a measure of radial flex of the sort that made the old 303 the first all-composite rim to win over the cobblestones of Paris-Roubaix.
The redesigned rear hub has a reshaped body with non-drive flange canted by 8degrees and the bearing shifted outwards by 7.5mm in the search for enhanced wheel stiffness.
Two colourways will be on offer: Beyond Black and Falcon Grey, which will have silver spokes. Expect the wheels to reach the UK in October 2011.
Prices will be based on €2200 per pair for the tubular version and €2500 for the clinchers.
