I recently fitted polyurethane cush drive rubbers but had to trim them down to get the whole thing back together as they seemed massively oversized. A friend who is a bike mechanic managed to get them to fit without trimming by liberal use of WD40. Perhaps I over-did-it and negated the value of new rubbers? I think I'll take the bike and have one of these guys ride it and see what they think. New cush drive rubber and or a new chain would be a great solution.