Replacing drivetrain on a 1990 Diamondback Ascent
I am looking for your advice on replacing my drivetrain.
I have a 1990 Diamondback that I use as my daily commuter. It is outfitted with the original Shimano Exage 400 group. It is a 7-speed RD. The freehub is Shimano HyperGlide system. The shifters are integrated brake levers/index shift levers. The crank is of the Biopace type
Lately I have been having trouble with the rear derailleur. I adjust it about every 200 miles, but within a few days the chain starts to make noise, skip a cog, refuses to shift at al, or shifts on it's own.
When i brought it in for service earlier this year, the mechanic at the LBS mentioned that the rear index shifter was about worn out and may have to be replaced in the near future.
The FD and crank seem to be in good shape
So the time has come to take some action. I have a few scenarios that i can think of:
1. Replacing index shifters and housing.
I was thinking of the levers and cables/housing to start with. Does Shimano still make index shifters that work with a 7-speed? Do you think that this will solve the issues described above?
2. Replacing the rear derailleur
Does Shimano still make 7 speed derailleurs? When I look at their websit it is all 8-speed and up. Should ei replace the shifters as well in this case?
3. Changing the rear derailleur to an 8-speed.
Would it be worth and possible to change the rear derailleur to an 8-speed. I do understand that I need a new cassette and chain in that case as well, in addition to changing the shift levers and cable/housing. Could I still keep my Biopace crank?
Could you comment on which of these scenarios make sense from a material and cost standpoint?
Sorry about the length of this post. I appreciate any advice