When I pedal while standing, the chain hops off to a smaller cog. This happens when I "tilt" the bike, as we do when stand-pedal. I am not really sure why this happens, but I think the chain is loose. Is the solution to get a new chain, or is there something I can do?
I lean against getting a new chain, since my current one is ugly and rusty (I have not maintained it very well over the winter!)