So I've been recently playing around with Electric Bikes --- they are awesome! I highly recommend that if you have some free time and about a $1000 dollars lying around that you make your own 50kph (32mph) Electric Bike.
Parts for Electric Bike:
Crystalite HS3540R Brushless Hub Motor (1500W)
Cycle Analyst (for measuring speed and current draw)
Hobbyking Lithium Polymer 150W Batteries (2x)
Ecrazyman Brushless Controller (72v @ 45A)
Brat Broodie Bike Used (Any used Bike Frame with Front Suspension)