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I've got a vintage road bike with no braze-ons for shift cables: Instead, it's got a cable stop holding the cables against the downtube and parallel to the chainstays. Unfortunately, it seems to slide up the downtube with use, which not only causes the shifting to get all wonky and eventually fail but it also has created a nasty, long scratch along the underside of my downtube:

Photo of cable stop with indicator describing unwanted movement

Moreover, I'm not sure if this is aggravating the problem or not, but the shift lever for my big cog only travels through half of its whole motion before the cable becomes so taught that it doesn't go any further — If you apply enough pressure at this stage, it makes some angry creaking noises, which I assume to be the cable stop moving (but I can't be sure without methodically trying to reproduce it, and thereby causing even more damage to the frame):

Shift lever at maximal point of travel

How can I fix my shifting setup so that it doesn't go out of whack due to the cable stop moving under stress? — I've tried putting rubber tape between the cable stop and the frame, but that doesn't seem to accomplish much (as visible in the photo above).

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  • Full length cable housings could do an end run around the issue of cable stops. Modern housing is very good with little friction. This old system solved the problem of high friction cable housing that is no longer used. The only downside is if the bike needs to maintain vintage parts or look.
    – Rider_X
    Jan 17, 2017 at 22:25
  • It sounds like the strap around the tube is simply not tight enough. If there is no gap left between the mating sides of the screw-together junction then you should use some shims such as Carel describes. Jan 18, 2017 at 1:07
  • @DanielRHicks it is not possible to tighten the strap further without stripping the screw head. Jan 18, 2017 at 6:43
  • So, use the shims. Jan 18, 2017 at 12:50

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That calls for a shim. Cut a narrow strip from a drinks can, about 3-5cm long and lay it under the cable stop before re-tightening the screw. Make sure all the surfaces are clean and degreased. The soft aluminium of the shim will 'absorb' the remaining roughness of the tubes and the cable-stop and make slipping more difficult. (I've solved the problem of the brake lever rotating around a steel handlebar in this fashion.)

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    This could work well, if done neatly. The underlying cause is a loss of pressure or tension on the band-on strap, caused by the metal stretching or the mounting bolt distorting. OP might also get away with adding some suitable stainless steel washers under the mounting screw's head.
    – Criggie
    Jan 17, 2017 at 23:43

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