Preventing downtube cable stops from sliding out of place 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:



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 &mdash; 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):



How can I fix my shifting setup so that it doesn't go out of whack due to the cable stop moving under stress? &mdash; 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).
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.)