Originally Posted by
bradtx
FixedFiend626, A problem that could arise is the backside of the FD cage will interfere with the middle ring when shifting to the outer chain ring, if the difference between the middle and outer chain rings isn't great enough. I have a FD meant for a 52-42-30T triple barely clearing an eight tooth difference, but it's also working on a smaller diameter 24-34-42T chain set.
I'm guessing that you're credit card and/or lightweight touring with that crank set. A less expensive option is to use a cog on back with one or two more teeth. For example:
48/15=~86 gear inches
52/15=~93 GI
52/17=~82 GI.
Brad
One thing I failed to mention is that Im running a bottom-pull, down-swing derailleur and due to the waterbottle bosses being lower than usual I can only lower the derailleur by about a cm so that kind of solves that potential issue (of backplate hitting). Whether itll be too high to actually shift it to the 46 might be an issue. might have another top-swing derailleur in the parts bin.
The last paragraph you wrote I literally have no idea what youre talking about. Credit card with that crank set? and thing about gear inches? its not a singlespeed.. quite confused.