Edit: I'm now worried the main issue might be if it's at all possible to mount cable stops to the top mount position the cables exit the DT into the shifters. As I mentioned, I'm not there to take more photos at the moment, but you could see a bit better if you open the photo attached to max size.
I do actually prefer STI, realized this after posting. need to understand if that's ruled out, and if so - if there are any SIS shifters that would fit as replacement.
I hope there's a solution that doesn't require serious engineering.
Edit 2: Attaching pics I found for someone with roughly the same bike who performed the same conversion I'm trying to make.
It requires some machining, but if I can do that, it might be the better option in my opinion over SIS. *I still don't even know if I can get SIS shifters to fit the mount I have.
Also attaching better pictures of my top mounted shifters - fitted on a boss that isn't identical, although the machined part I require is probably the same.
For the part I need to prepare, I'm still waiting to hear from the owner of the bike in the photo, hoping to get a few more angles and possibly dimensions so I can replicate it. I'm curious about the reverse angle, probably showing how the exposed cables go into the new piece.
Surprisingly this seems more crude than the guide system on an earlier 80-81 model, with a practically identical frame:
This is continuing another thread I started, asking advice on whether I should buy a used groupset.
The most thorough advice I got there, suggested replacing my 6s freewheel to a 7s one, and couple that with 8s STI shifters - my purpose was actually converting to STI.
I'm now trying to figure out if I might be better overall converting to 7s SIS.
Arguments for 8s STI:
- I was told 8s STI shifters should work fine with a 7s freewheel, and that even the people at Shimano said so.
- Brifters are easier to use.
- some people say 8s shifters with a 7s freewheel isn't a perfect match
- I'll have to use cable stops, I'm still not sure how to go about this on my frame - the tutorials I saw had the break cables routed outside the frame, not inside it, and they were also positioned at the side of the downtube
Arguments for 7s SIS: Its all pretty much said above -
- Should be no argument about compatibility with a 7s freewheel
- I don't have to deal with the cable stop issue, easier installation overall.
- Less comfortable shifting
- My old friction shifters were so finicky that I'm prejudiced against all downtube shifters
Anyone with experience and opinions to contribute? It would be great to understand if there's anything special I need to take into account considering the position of my current shifters and the routing through the tube.
Editing to answer a question I got: The frame is aluminum, with 126mm spacing. Which means it's not a candidate for cold setting, and therefore can't take anything more than a 7s freewheel - as far as I understand. And as Nathan pointed out in the previous thread I linked to, the dropouts are enormous and might not be great for flexing. I'm not there to measure the actual spacing, but the literature has it as 126