Not something I've paid particular attention to and never had a problem, but replaced a chain on my new 2x10 bike (never run 2x10 before) with a medium cage rear mech. Took out a few links from the new chain, found when on the 2 small cogs, the jockey cage was all the way back with the chain rubbing against itself as it comes back round through the jockey cage. Didn't like that, so took out one more link. All seems ok, but now when on the 2 largest cogs the jockey cage as stretched out to the front. This is ok once you're in the gear, but it makes a dodgey noise went changing. It's not a gear I use at all really, but seems I'm stuck between a choice of rubbing chain on the two small cogs or a potential issue on the two big cogs. How are other people's 2x10 set ups running in this regard?
I had no issues before with the original chain, but didn't take much notice. I couldn't compare chain lengths as the reason for the change of chain was my rear mech failed on the trail (casting snapped below the attachment bolt, twisted up the chain and I lost a few links in rigging up single speed to get me home.