When the bike is folded and used as a cart, the two main bicycle wheels are in front, side-by-side, while the caster wheel flips down and props it up from behind.

The hard rubber wheels you find on shopping carts are about the same hardness rating as PRO FLEX. Obviously, a bicycle tire is going to take a big printer.

The latest version of the cart–and a piece of the Wheelys franchise– costs $4,499. Someone in a popular location, like the beach in Santa Monica, can make as much as $1,000 in a single day ...

The wheels are designed to be low impact on the course. The gearing has been designed to be functional on varied terrain. The balalnce of how the bike rides, how the rack is set up, all that works ...