Actually to go 60 mph on 20" wheels only requires the motor to spin at 1000 RPM or so, easily doable by most electric motors. Torque can be controlled by changing the distance between the rotor and stator. Vibrations aren't usually an issue because there are no contact points between the rotor and stator. The biggest issue is usually the huge unsprung weight the motor adds the the suspension, so handling is definitely compromised and the suspension needs to be beefier...but its a bus