The Q128 is reputed to be not a great motor compared to the Q100. There is discussion on this on endless-sphere. As well as tons of information on the various winds of the Q100. I have a 201rpm Q100 on 700C, and I top out in the low 20s (mph) range, running on 48 V - (the "36V 201 version"). I'm overvolting the 36V controller (hence controller LVC is inoperative, relying on BMS for LVC). If you buy the Q128, it takes a different controller than the KU63 used for the Q100. The two controllers are not interchangeable, and the right controller will come with the kit, if you don't buy the parts piecemeal. There are other small geared hub motors "out there" - the FUSIN motors unit (I've bought from there in the past), and the small Maxus gearmotor from www.emissions-free.com, which is probably the pick of the litter.