Shimano 600 experts: Upgrade 6 speed to 8 speed
I recently acquired a 80's era Serotta with a full Shimano 600 set-up. I was thinking of upgrading this bike from 6 speed to 8 speed. I am usually Campy guy so my knowledge here is limited.
What components need to be upgraded? I want to keep the shifting to downtube shifters and run them as friction.
What I think I need: an 8 speed rear hub, cassette, and new chain?
Will the existing deraileurs work with an 8 speed upgrade?
One more thing, where can I find a headset wrench for that crazy starfish nut?