In some preferred embodiments, the dry clutch is capable of suppressing transmission of engine rotational fluctuations from the engine to a rider via a vehicle body. The spindle motor is furnished with a first thrust dynamic pressure bearing section, which is formed between confronting surfaces of the thrust ring and the flange section, and a second thrust dynamic pressure bearing section, which is formed between confronting surfaces of the thrust ring and the seal plate. The SSDC includes a retainer that provides a non-linear force resisting opening of the closure member.