The 104/64 was optimized for a 32T middle and 22T granny. You can fit a 21T if you can find one. 34T cassette not low enough?tooljunkie said:I'm would imagine that this has been asked already so I apologize. Is there a 20 tooth granny that fits the M760 Shimano Hollow Tech crank? I haven't been able to reliably locate one anywhere. Thanks.