Im not sure of your exact problem but have you tried setting the friction of the object you use for rails to 0 ?
its under "advanced physics" in the properties of the object...
Thanks, but that's not the issue. If you look at the ones on Venice beach 1080 they are quite a bit wider that the bike (to allow you to flip) which would suggest physics joint attached to handle bar extension. I can manage that but as soon as they hit the rails they collapse.
when you extend the handlebar, with lets say invisible cross-pipes,
remember to set their physic Type to: Contact Response, that way they detect collision even with no visibility.
this should do it....Also use point to point physic joints