The original 303 is Zipp’s most successful wheel, having been ridden to victory in the Tour de France, Tour of Flanders and Paris-Roubaix, and this new version looks likely to continue that success. Using the Firecrest principles in clincher form, it’s claimed to be faster and better handling.
Zipp’s Firecrest rim shape has a wider than standard tyre bed to produce a more rounded tyre profile that matches the curve of the carbon rim’s spoke bed, resulting in more balanced aerodynamics. The shape copes better in blustery conditions, with the front wheel being nearly immune to the effects of the wind. You can feel a pressure on the rim in a strong sidewind, but it’s more gentle push than violent jolt. In fact, we noticed a significant improvement in windy riding over a test bike with standard wheels.
Broadening the tyre bed also means the sidewalls are less prone to dramatic deformations when hitting a pothole or through high-speed cornering. Zipp claim that means fewer pinch-flats, and over the hundreds of miles we’ve been testing these we haven’t had any. At 1,579g a pair they’re pretty light too; you can find lighter standard road wheels, but none with aerodynamics to match.
It’s not just the rims that have received a makeover: the 88/188 hub set is lighter, with the 188 rear having a complete redesign. The non-driveside bearing has been spaced further out by 7.5mm to add stiffness, and the non-drive-side flange (where the spokes attach) is now canted by eight degrees, putting less stress on the spokes. We recommend that after your first few long rides you take some time to check the hubs – we had to retighten them after a couple of hundred miles.