My rear disc brakes will grab a little then release all together. I had tightened by cable at the brake handle so I loosened it but it still does the same. It is a Trek mechanical disc brake.

  • Is the cable slipping at the caliper connection point? It the nut was just tight enough to hold the cable but not tight enough to handle the increased tension this could happen.
    – Cory Roy
    Jun 18, 2015 at 19:11
  • Also if the routing is old there might be too much friction inside. If the bike didn't have maintenance for a while, a new cable and routing and clean and lubricate calipers and handle will probably solve it (and it's something you should do every once in a while).
    – super
    Jun 19, 2015 at 3:18

2 Answers 2


On mechanical disk brakes it is pretty common that the caliper is broken: the spring inside it just slipping when enough power applied (yet this power not enough to brake).
It is easy to check it: push the brake lever and look what is released there: the cable from the nut, or the caliper itself jumps back.
Probably you should replace the caliper.
New calipers coming with new pads, so it's a good time to clean up the disk with a good degreaser and maybe a sandpaper to save the new pads from all its garbage.


It's common issue. Most likely brake pads have worn out. Else the likely cause is dirt inside the brake disc mechanism. Open the brake disc mechanism, clean both brake pads on both sides. Also the mechanism which drives the brake pad front and back may have some burr or dust stuck inside which causes the brake pads to slip. The spring which drives the brake pad is not able to push the brake piston front thereby causing the release of disc brakes altogether. Just clean and your brakes should work.

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