Originally Posted by
BobFishell
6,7, and 8-speed systems have the same cog spacing, so you can use brifters made for 8-speed drivetrains. The lowest position on the rear shifter corresponds to your lowest gear. This leaves you with two extra positions at the top end, but all that will do is put some slack in your cable. I used a setup like this with a 7-speed freewheel on one of my bikes before I adapted an 8-speed freehub axle to work with 126mm dropouts.
The trick is finding 8-speed brifters. I think Shimano Sora is still 8-speed, although I'd try to find some NOS 105 or Ultegra components.
Sora was 8 for ages, the ones with thumb shifters, a la Campy, but in their last year they went to 9 speed, but still thumb shifter, and then they did a whole "trickle down" down and changed sora to be very similar to the old 9 speed Tiagra brifters, with the paddles instead of the thumb thing.
the thumb soras work, but I found them kinda stiffish, certainly compared to my 9 spd tiagras, and when they went sora paddles, they felt just like my 9sp tiagra (bought some paddle Soras to replace a broken 9 sp thumb sora on my wifes bike about 3 years ago)
isnt the issue the cable pull? Using 8 spd brifters on 6 spd.
I admit I dont have the knowledge about this