Originally Posted by
MadBuddha1
Well most 7 speed derailers wont have the range to say accomodate a 12-29 9 speed cassette, it'll shift fine through most of the gears because you're correct about the indexing being in the shifters but the cage and spring etc is only so long, just saying to visually check the range of the RD sans chain before installing the shift cables
I've never come across a Shimano "7-speed" rear derailleur that wouldn't sweep the full width of a 8, 9 or 10-speed cassette. All you have to do is adjust the limit screws correctly. At the moment, I have a bike with a 7-speed STX rear derailleur with an 8-speed cassette using 105 8-speed brifters and it shifts just fine.