Large numbers of bearings are used in motorcycles. Actual numbers will vary depending on the model and other structural factors, but a single motorcycle will have between 20 and 30 bearings built in. These bearings are used in key revolving parts, supporting the vehicle's running, including in the engine, the transmission, and the wheels. They help to reduce friction and to ensure that the motive power of the engine is reliably transmitted to the wheels. http://www.awategroup.com/chrome-steel-bearing/motorcycle-bearing/