2_i 

The chain transmits a lot of force - after all it propels the bike. The pulley axle bolt provides quite a bit of leverage. I know that it can be hard to believe, but every time this Ti Parts pusher is put on the bike, the chain will free itself mangling on the way the tensioner pulley. The only question is whether this will happen before the next corner or two more blocks into the ride. I put the pusher on and took it off and swapped the pulleys. I can leave a loose bolt once in a blue moon, but not every time this pusher goes on. The chain never ever freed itself with the original pusher that is now back on the bike - for now everybody lives happily until I try another junky aftermarket part By the way, as may be evident from the photo, the width of the pulley fills in practice completely the space between the rollers. You can only create an opening for the chain to escape by pushing the pulley away, nominally kept put by the tensioner arm.