Originally Posted by Andrew R Stewart

Do you know how the system worked before you replaced the chain? Generally a narrower chain results in less rubbing at either end. The 6,7,8 speed chain should work well enough and is what many mechanics recommend these days for even 5 speed systems. But the new chain will act somewhat differently in a few aspects.

The chain is likely more flexible. So a greater amount of overshift and trim back often is called for. The narrower width can sometimes not settle into the small ring's teeth when down shifting. It can ride up on the tops of the teeth and drag along the big ring's inner side. The side plates are likely less "tall" or don't extend as far away from the roller. This makes the amount of lift up for the chain to clear a smaller cog will be less. But this also means that the chain will want to partially
derail" off the lower pulley and drag along the cage's plate. This can be more problematic with worn pulley teeth, a misaligned cage/pulley and/or cross chaining.

It's hard to really understand what's going on so this is all I got for now. Andy