kalash74

I'm now trying to get my 1986 Bridgestone MB-2 in working order. I noticed that the left thumb shifter for the front derailleur is not holding. When I shift and it makes a clicking sound, the derailleur cage reverts back to its original position. I have tried tightening down on the top screw, but it doesn't seem to always work. It makes the shifters harder to shift.

The shifters in question look like these
https://i.ebayimg.com/images/g/nxcAAO...VP0/s-l300.jpg

Also, even though it makes a clicking sound, I assume these are friction shifters, not indexed?

Finally, I noticed that the shifting cable wire wraps around underneath the bottom bracket. Seems like the cable would be creating a lot of friction with the bike frame. I'm assuming that this is the way it was designed, but could this be part of the problem?

Any thoughts on what to do? Replace shifting cables? Thumb shifters too? I'm quite inexperienced when it comes to derailleur drive trains. (Almost all my bike mechanical skill is single speed and SA 3-speed hubs).

fietsbob

Falcon , they are sold in a pair bagged with cables for only $20... cheap and cheap to Replace .

You also could 'win' some old nicer quality older levers at auction

or there are thumbie adapters to re mount friction down tube levers on the handlebars..


I had a friction shifted 3 speed hub on my bike, in 1957..

Andrew R Stewart 

The lever's clicking isn't an aspect of any shifting control except an audio feedback as to how far you've moved the lever. The clicks are a spring loaded part that rides over a fixed and notched part, no function as to how much cable get's moved (like a true indexed lever's clicks do). One could defeat the clicks and the lever's cable movement would be the same.


It's possible that the lever's pivot and the friction plates have gotten miss positioned so that the tension wing bolt only tightens the plates/washers against each other and not letting then freely float on the pivot stud so they can press against the lever's hub.


But as FB said, these levers are pretty cheap to replace. Don't worry about the cable touching the shell. If kept free of ruse it will move freely. One could buy a plastic guide and install it on the shell's underside if one really wanted to do so. Andy.

coominya

Why not pull it apart and have a look at the components, you might see something obvious that can be corrected. I suppose you have tried adjusting the derailleur itself? I just corrected an identical issue on an early 90's Trek with indexed gears. It would slip back off the large chain ring after changing up. What I did to fix it in my case was to loosen the inboard limit screw which allowed the derailleur to move outward a little more and stay out.