Pondering converting my 1990s Trek 6500 MTB into a tourer. It has the original 7-speed cog and derailleur on the back.
1) Can I assume this is a cassette (lock ring) and not a freewheel, and that a 9-speed cassette would slip on and work? Does a 9-speed cassette take the same width on the hub as the 7-speed currently does?
2) And if it would work, if I then converted the 7-speed Grip Shifters to Shimano 9-speed bar ends, would the 9-speed bar ends control the current derailleur up and down the 9 cogs correctly?
I’m thinking it would, as all the rear derailleur does is move the pulley arms the amount allotted by the shifter, meaning the shifter and cog must match, but the derailleur itself just has to have enough range (and capacity) to span the cassette range.
Bottom line: I’d like to be able to just add 9-speed bar ends and a 9-speed cassette, retaining my current derailleur and wheel hub. Workable?