[G-Force Junkie]

For 2 sport bike, a 5x8 will work. A 6x10 will be a little easier. Its possable to get 3 sportbikes on a 6x12, but I would go to a 7x14 if your going to do it often. FWIW, here is my 5x8 (3.5K axl, 15" tires, built like a tank)