I posted this in the mechanics section but got no replies so thought I'd try here... I'm a newbie to aero type wheel sets and I just bought a used wheel set for my tri bike advertised as a 2006 Zipp Clydesdale 404 Wheel set. The price was good ($850 including Conti tires, Shimano cassette , Zipp skewers) but I just realized the front wheel rim decal says 404 and the rear decal says 909 - they look exactly the same with regard to rim depth (both 58 MM). The Front 404 has 24 spokes and the Rear 909 has 28 spokes (Clydesdale version) So, my questions are: Why one wheel in the set would say 909 and one say 404 if they have the exact same 58 MM depth? A phone call to Zipp was a waste of time. I'm guessing the 2006 909 is maybe the same as a 404 just what they used when selling a 909 set (what the LBS told me) Is this a good combination? Or is it better to have two 404s???