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'll be more certain. Interference by the inner cage plate of the front derailleur WILL occur unless you have a very old fd. Most relatively new front derailleur designs are made for a minimum chainring tooth difference of 10 teeth or more and have deep inner plates.
The half-step gearing FBinNY refers to was common up to about the mid 80's when 7+ cog freewheels and cassettes reduced the need. Before that, front derailleurs often had shallow cage plates and would clear even a four tooth difference. I had a 1985 Bridgestone with Sun Tour ARX derailleurs and the front derailleur permitted me to use a 46/42/26 triple crank. Nothing I've owned since then will work with that gearing.