Seriously crazy idea?
 

This looks nothing if not unstable, but it could be fun, if there was a way to make the corners work....

http://www.instructables.com/id/Cart-Bike/

http://www.instructables.com/id/Cart-Bike/

Probably suffers a bit of understeer.

I like this implementation better
http://www.bicyclelaneindustries.com/bli/cartbike/

that is great!! thanks for the link! :)

I don't know but last time I pushed a cart into the corral at menards, the rattle from the pavement drove me crazy, don't think I could ride any distance without going bonkers.

Turning could be managed by modifying the steering to get rid of any rake, that way regardless of turning the wheels would be on the same plane and eliminate any tendancy to lift.

Ken.

Might have left his front wheel at home when he drove an hour to that group ride. Been there, done that.