Mercury Wheels S9C Carbon Road Wheelset. When it comes to aerodynamic, high performance road wheels the Mercury Wheels S9C carbon wheelset is in a class of its own. Their carbon fiber rims are plenty deep at 80mm, plenty wide at 23.5mm, and have been race proven by the SmartStop professional cycling team. The S9C wheels are the perfect choice for any event on flat roads where aerodynamics play the most important role. Whether it is a time trial, triathlon, long road race, criterium, or simply your weekly group ride, the S9Cs help serve up blazing speed. And don't fret about crosswinds the rims have a rounded trailing edge to help you stay stable during any crosswind situation. Additionally, the S9C's rims are a solid 23.5mm wide, which means you can run lower PSI for a more comfortable ride that corners with unparalleled confidence. Wider rims also have some counter intuitive effects when compared to those standard 19mm rims: they actually decrease rolling resistance and increase aerodynamics.