1

I've searched this site for this issue but it appears other questions/answers relate to old cables/housing. This specific problem happened after replacing both (link to Shimano brake cable set- https://www.amazon.com/gp/product/B0050LUBZ8/ref=oh_aui_detailpage_o03_s02?ie=UTF8&psc=1).

Having neglected my brake cables/housing for many years, I've gone ahead and replaced the cables and housing on my 2012 Trek 8.3 DS. This seemed like a very straightforward repair, so I went for it. Interestingly, the old cables didn't have much rust on them but I went ahead and replaced them anyway assuming the stretch would affect performance.

Long story short, I cut everything to essentially the same length and fed the cables/housing through all the various caps and grooves in the exact same way the old, factory installed cables were. Upon squeezing the brake lever I am finding some of the housing shifts and even pops out of the grooves on the underside of the top tube. This, of course, "resets" the tension and suddenly I have a significant amount of slack in the cable.

I should mention the end caps on the housing were a wider diameter than the pre-existing ones so they didn't fit well into the plastic caps that preceded bare wire running the length of the top tube. Reading the product description again, I'm seeing the metal pieces are all considered end caps (MTB/Road). I put these onto the housing where the housing ends so perhaps this is causing problems (the original housing has metal caps at the ends).

After reading up on this site on similar issues regarding older cables/housing, I see many asking if the cables had recently been lubed. I've read in a few places I shouldn't be lubing brand new cables since this will attract dirt. I'm not sure what to do since this friction within the housing could also be shifting the housing around after applying pressure.

I'm also noticing there is zero "spring" tension pulling the cable back after applying pressure to the brake lever. Might this also be a factor?

Thank you for your help!

  • So you are saying when brakes are applied the housing is dragged back by the moving cable, and comes out out the cable bosses on the frame? This must be the rear brake as looking at a picture of the bike the front appears to have full length cable run the the caliper. Are you also saying that the new cable does not fit well into the cable bosses on the frame because the end caps are wider than those on the old cable? – Argenti Apparatus Oct 3 '17 at 11:47
  • @ArgentiApparatus - All three points are correct. I've started with the rear brake first which of course is more challenging. I was not under the impression this would be a difficult repair. – Andrew L Oct 3 '17 at 11:52
  • Do the end caps not fit in both the front and rear bosses on the top-tube? How about in the brake caliper itself? – Argenti Apparatus Oct 3 '17 at 12:29
  • Neither on the top tube, however these end caps do fit into the brake lever and caliper. – Andrew L Oct 3 '17 at 12:35
  • BTW, how did you cut the housing? – Argenti Apparatus Oct 3 '17 at 12:36
4

Some of the problems I encountered when doing this recently:

  • forgot to make sure the brake handle wasn't a little bit squeezed as I did it
  • forgot to use the brake handles fine tuning to increase the tension after installation
  • when cutting housing, forgot to use a pin to unblock inner sheathing at the end of the housing (the cable then pierces the end and catches)
  • I too had ill-fitting caps; I made some by wrapping narrow strip of duct tape until I got the right thickness
  • I forgot to oil the inside of the housing
  • I failed to cut the housing long enough to always have a decent bend creating pressure to keep itself jammed in
  • All great advice. Will certainly be mindful of each as I take another pass at this tonight. – Andrew L Oct 3 '17 at 13:51
  • Modern outer cables are teflon lined - you don't oil them any more. – Criggie Oct 4 '17 at 0:38
  • I do, for the following reason which may simply be my overactive imagination. I fill the empty housing with lube so that when I push the cable through, it creates a little bit of pressure ahead of the cable to flush out any dirty and make the sheath inflate out like blowing into rubber gloves before pulling them on. – curly Oct 4 '17 at 1:29
  • Marking as answer because oiling the cable seems to have fixed it. They are indeed teflon lined but still had enough friction to pull the housing out. Thanks! – Andrew L Oct 15 '17 at 11:56
1

If a segment of housing is being dragged back by the moving cable, and comes out out the cable bosses on the frame, then there must be binding on the cable in the affected segment. This would also explain why you are feeling reduced or no return force at the brake levers.

You can probably diagnose where the binding is and what is causing it by removing each housing segment from frame bosses, calliper or lever, and seeing if it moves along the cable freely.

Check the ends of the housings where they were cut. Deformed ends or burrs in the metal or mangled inner liner might be causing binding.

More worrying is that your housings do not fit into the frame cable bosses properly. The housing should fit all the way into the bosses. Housing coming out of a boss would obviously render the rear brake inoperable.

Is your new housing the same diameter as the old? Can you use the old end caps on the new cable?

  • 1
    The housing alone fits but I think the end caps (which very closely resemble metal parts affixed to the factory original housing) I believe may be meant for the cable itself. Also, I am cutting the housing with the cable cutters and it seems to be making a clean cut. I will use an awl/file to ensure it is opened fully. Will report back with progress and mark as answered! – Andrew L Oct 3 '17 at 13:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.