Originally Posted by
AMoney
I'm a bit confused. I thought that only front derailleurs had trim.
You're both right. Only front derailleurs have 'trim' positions but you can refer to adjusting the rear derailleur indexing as 'trimming' the derailleur. There are so many good videos on how adjust derailleurs that you should be able to swap back and forth whenever you want/need to. I'm really surprised that you haven't done this yet, it's very easy. It's a much faster way to learn things like this than coming to a forum and getting all sorts of random suggestions. At the absolute worst you totally f it up and have to make a trip to the bike shop.