I use my bike everyday to commute and recently I've noticed that when in gear 24 my bike seems to slip from time to time as though the chain has "lost the gear" and then finds it again.
I haven't changed gear and when I change down into gear 23 the problem goes away. I'm thinking it must be a problem with my cassette/derailleur but I'm not sure what the problem would be. I'm kind of a novice when it comes to bike maintenance but I was wondering whether anybody could tell me what I should do?