That's my main complaint about the Rocky's; there aren't really bearings. They're just plastic bushings that they tell you to use some waterproof grease on. If it's too tough to crank they tell you to back off the center bolt holding the crank to the roller, but there's no lock washer or anything to keep the bolt from eventually loosening up and falling out.

But the frames and crank are metal and the tube they can provide is a pretty light weight, but rigid one.