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The question is somewhat related to this one.

I have cantilever brakes with this rear Tektro hanger (but the hanger itself instaled downwards): Tektro rear cable hanger

The problem is, when I brake the hanger rotates, which causes too much play, and the STI brake shifter almost hits the handlebar. If I adjust the cable by tensing, the pads scratch the rim.

Should the rear hanger rotate? How can I adjust the system to remove the free play caused by the hanger?

homocomputeris
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    A few good pictures of how you’ve installed it would probably help. You could also post pictures of how the cables are installed at the handle bar (preferably without tape). Is it really flexing that terrible even with normal braking forces? With two hands and full grip strength you can make almost any brake system’s brake lever hit the handlebar (good to test the cables and cable housing, but unrealistic). – Michael May 19 '18 at 13:24

2 Answers2

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Ideally all parts of the brake system that hold the cable housing should be fixed and immovable. There are two problems that can occur if this is not the case:

  • Flexing or movement when the brake is applied and there is tension between the cable and housing: This reduces the force that can be applied at the brake caliper and is obviously a bad thing.

  • Movement of the housing as the brakes are applied and slack in the cable is taken up. The brake lever has to be moved too far before the brake pads touch the wheel rim.

Sounds like you have the second problem. When the brakes are released the springy housing is moving the brake hanger causing you to have too much slack in the system.

The fix is is to get the cable housing under control so that it cannot flex and move around. The housing may be a little too long or not anchored the the frame properly. You can try fixing the brake housing to the frame or seat post with a zip tie to hold it in place. A zip tie around the seat tube end if the hanger to make the housing enter into it straight might work also.

Ideally, there should be a little tension in the brake cable when the lever is released so that the housing is held in line. This tension is supplied by the return springs of the calipers. Check the calipers to see if the return spring force is too weak. There are typically adjustment screws on the calipers or a array of holes on the brake bosses that the end of the spring fits into for adjusting spring tension.

Update after reply from OP in comment: 'I have shifter-type compressionless housing ...'

Shifter cable housing should NOT be used for brakes. The forces generated by brakes are much higher than those generated by shifters and derailleurs and the housing may fail.

See this answer.

Argenti Apparatus
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  • There is no slack in the cable, and I have shifter-type compressionless housing from Jagwire. The housing moves because of the hanger, so I can try zip-tie it to the seatpost. Thanks for the advice. – homocomputeris May 19 '18 at 12:59
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    I think this problem can’t be caused by too long housing. A few centimeter more or less housing won’t cause noticeable compression. However, housing which is too short and therefore not properly seated in the cable stops can be a problem, especially under the bar tape and around the seat post. – Michael May 19 '18 at 13:05
  • @homocomputeris. If you are using shifter housing that may be part of the problem, and is a really bad idea. See edit to my answer. – Argenti Apparatus May 19 '18 at 13:17
  • @ArgentiApparatus It is shifter-like housing Jagwire Road Pro Brake. The problem exists with both types of housings. – homocomputeris May 19 '18 at 13:41
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Is the hanger perfectly in line with the rear brake? A (free running) cable will always try to run in a straight line. If there is an offset the cable will bend the brake and the brake hanger into a straight line, which is bad.

Michael
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  • I think this is the case. I just don't understand why the hanger is not just one solid piece and moves. Is it by design or 'we have this, and it'll do' attitude. – homocomputeris May 19 '18 at 13:09
  • It has those hinges so that it can move and is then almost only under tension, like a cable or chain. That’s why it shouldn’t actually bend or flex but only stretch ever so slightly (should be imperceptible). – Michael May 19 '18 at 13:28