rami_94

I recently mounted a new shifter for the real derailleur along with a new cable. I routed the cable along the frame inside plastic tubes.

I managed to adjust the shifting so that it's crisp. I shift a couple of times up and down and the cable becomes loose again! I can't figure out why this happens. It's quite fixed at the derailleur side. The shifter at the handle bar is at a new position more towards the center of the handle bar. It's an old vintage city bike.

Any idea why this keeps happening?

Thanks in advance!

andrewclaus

Please explain the "plastic tubes" used for routing. If you're not using properly mounted shifter cable housing, this problem will continue. If you are, and you installed the proper end ferrules, it's not uncommon for the housing to take a few shifts to set completely into the ferrules, making the cable loose.

You'll be able to post photos after one more post, and that would help.

rami_94

Thanks for your reply. Yeah I don't think these were proper tubes. I used old brake cable tubes for the job. I didn't realise this would be a problem!

I'll buy new shifter cable housing hoping this would do the trick.

Andrew R Stewart 

Do know that full length cable housing, even with the right stuff, has more compression and resulting loss of shifting "crispness" over time then external and segmented routing does. Andy

andrewclaus

What Andy said above, plus brake housing is 5 mm diameter vs 4 mm for shifter housing, and the ends don't fit well into the shifter and derailleur. If you didn't terminate the housing properly, it will keep shortening and the cable will keep getting loose.

rami_94

Alright, I guess I'll take my bike to the bike shop with me and get professional help with buying the right parts. Thanks for your help!

HillRider

One other thing to note. If your inner cables are "Teflon coated" be sure to scrape the coating off where the cable clamps to the derailleur. Otherwise they will likely slip no matter how tight you make the clamp bolt.