Shimano's WH-9000-C50-CL wheels represent a collaborative effort between professional racers and engineers with a heavy dose of wind-tunnel testing thrown in. The C50-CL wheels exhibit Shimano's world renown build-quality plus a D2 rim design with a 50mm profile and 23mm width. A blunted leading edge optimizes both aerodynamics and stability in high winds and tricky descents. Braking performance is optimized with an aluminum braking surface so no special brake pads are required.
The WH-9000-C50-CL is 11-speed compatible and comes with a 1.85mm spacer so it will work with 10, 9, 8-speed and SRAM too. Other differences over the WH-7900 wheels include improved hub flanges that are 7mm wider for increased strength and a now 100% titanium freehub body for lower weight. Styling is a bit sharper with a new black anodized hub finish and black spokes.
The hubs are based on Dura-Ace design featuring angular contact bearing and labyrinth seals, however vary a bit by offering straight pull spokes and a wider stance for the spokes. The flanges are super wide increasing the distance of the spokes between the flange creating a wider footprint for a far stronger and more stable wheel. The spokes are bladed. The front wheel is 16 hole with a radial lace, while the rear is 21 hole with a OptBal 2:1 lacing meaning there are 14 spokes on the drive side and 7 on the non-drive to enhance rigidity and durability. OptBal balances spoke tension meaning no spoke breakage and wheels that seldom need truing.
In case you are wondering, the "50" designation refers to the rim profile in millimeters while the "CL" nomenclature means this is a clincher wheel designed to be used with a standard clincher tire and tube. Shimano includes a pair of the best skewers in the business. Also includes rim tape, valve extenders, spoke wrench and wheel bags.
When installing a Shimano 11-speed cassette use no spacers. For Shimano 10-speed use the include 1.85mm spacer plus the 1mm spacer included with the cassette. Just use the 1.85mm spacer with a SRAM or Shimano 9 or 8-speed cassette. 145psi maximum tire pressure.