'[QUOTE] The one I rode was a trike: two wheels fore, one wheel aft. The only real prob was that the chain run was so long to the rear derailleur that there was a lot of slop in it and it kept coming off, but then it could have just been set up badly.[/QUOTE] It probably was (or at least not properly adjusted for you). On a properly set up tadpole (2 wheels front, one rear) trike the chain will stay quite happily where it belongs - it's just a matter of getting the tensioning right.