Zipp Cassette Body, Freehub with Ceramic Bearings, 2005 - 2008 Free Shipping to all U.S. Locations The ability to quickly switch between SRAM/Shimano cassette bodies is one of Zipp hubs' many great features. Ceramic bearing upgrades are available. Si3N4 (Silicon Nitride) Ceramic Bearings The ultimate hub has to have the ultimate bearings. Silicon Nitride (Si3N4) ceramic bearings are 30% lighter than steel and 40% stronger. So finely balanced, they have an incredible maximum spin rating of 300,000 rpm under load. Manufactured in matched sets of 15 balls per cartridge, they exhibit variance in size and sphericity of LESS than 2 millionths of an inch among the entire bearing set. Each ball is over 1000X more round than the best steel bearing of any type, grade or benchmark. At 25mph, the calculated energy saving from these alone is 0.8 to 1.0 watts over the standard Zipp Ultra-Precision Steel bearing (this is analogous to saying the F430 is the standard Ferrari!) and nearly 2 watts over traditional high precision steel bearings available in high performance bicycle hubs. On an 8% grade, the reduction in friction is the equivalent of a reduction in static weight of 340 grams! A custom Teflon thermoplastic retainer physically separates and locates each individual ball within the bearing race for optimum performance and longevity. Further protection is provided by a custom-formulated 75% fill of barium-hydrocarbon ceramic specific grease. Double light contact seals on polished races provide a final near friction free protective barrier against the elements. The bearing races themselves are a hybrid ceramic specific alloy finely ground and polished to a ABEC7 standard and cryogenically treated at -300 degrees Fahrenheit to refine the molecular structure. These should absolutely not be confused with the ceramic bearings flooding the market from China and India, many of which use ball and race tolerances equal to or worse than high precision steel bearings. The standard Zipp steel bearing uses a Grade 10 ball (the Ceramics use a Grade 2, the finest available) and ABEC5 races, while most other ceramics on the market are using Grade 25 balls with an ABEC1 or ABEC3 race making them actually less efficient than the standard Zipp Ultra-Precision Steel Bearings. These bearings are the absolutely highest grade and tolerance ever available in the cycling industry, and have been supplied by Zipp to no fewer than 5 Pro-Tour teams winning more than 20 Tour de France stages, more than a dozen Spring Classics, over 30 World Championship medals, and countless Ironman victories including the Ironman World Championships.
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