I've been upgrading two vintage bikes this one. One is a new to us Santana Tandem and the other is a Gary Fisher MTB.
In both cases I have changed the drivetrain.
My experience has been that changing the crankset or the FD results in huge difficulty finding a combination of crankset, FD and shift lever thy work properly. The upgrades to the rear are easy, even if they require changing the cage on the RD or buying a new RD. You will be able to find a combination that works.
Your lowest gear is a 39-23 which is about a 1.7 ratio. I'm a little older than you and find I need a 1:1 ratio, but like a 0.75 ratio. A 41 largest tooth cassette would give you a 1:1 ratio and fit right on.
Shimano Deore Derailleurs are in the $35- 75 range on Amazon. 8-Speed 11-42 Cassettes are in the $45 range.
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Cheers, Mike
Last edited by PromptCritical; 04-21-24 at 02:31 AM.
Reason: spelling