get a bike where they don't dangle on the tank.
Seriously though, it would bug me as well, and I would hate keeping separate key chains. How big is your keychain that it is dangling over your tank?
I only have the house key attached with the bike key at the moment and its not scratching the tank, but it's still metal rubbing on metal when I'm riding. A scratch anywhere is a bad scratch.
Ok OP dont listen to the trolls who are calling you stupid for posting this question. I had the same issue and had to come up with my own solution. Hear is what i did.
First you need to get yourself a large plank of wood and three strong steel chain links.
Glue the chain link equidistant around the inverse aixs of the wood. Boom no more issues
any pictures? Thanks!