Rear wheels

What is to stop the rear wheels working themselves loose and falling off also can you tell me the purpose of the question about the terrain weather it has lots of hills is there different gearing options

Hi Steven, The rear two wheels have never fallen off, so there's nothing to worry about - it is the bearing that spins, so that bolt that holds them stays in one place. What changes with the terrain selection is the small gear sprocket, slightly helping on said terrain. For example, the flat will give you just a bit more speed on flats, while the hilly will make it a bit easier to climb hills (up to 8%). Here you can learn more about it halfbikes.com/how-does-the-halfbike-perform-up-hill