if i were you craig i would stick with 24v. bosch motors burn out on 36v. i have learnt lessons over the years and 36v would be fine for a competition or if you were to go on tv but if you are doing live events as part of your main hobby then realibility is the key. most speedos blow when there is something wrong with the robot i.e. jammed gear or short on the wiring. 24v bosch will be fine with your big wheels and will prove to be a lot more realible. just my opinion that is.