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Brake leaver slipping / snapping - fixable without new parts?

buddhahatbuddhahat Posts: 16
in Workshop
I was out today and my rear brake lever made a snapping sound and went completely loose.

I had just tightened the barrel adjuster on the rear brake. It’s a TRP Spyre Type C mechanical disc brake.

What’s strange is that when I loosened the barrel adjuster a bit the brake lever seems to be pulling the brake again so it doesn’t feel like the cable has actually snapped.

My question is: What causes this snapping/slipping issue?

Is this fixable without new parts? I had the cable replaced at my LBS a few months ago so would rather not pay for new cable again if avoidable.

Any advice would be much appreciated.

Best,

B

Posts

  • oxomanoxoman Posts: 11,738
    Doesn't sound to good to be honest, sounds like you over tensioned it and the internals have partially dislodged or broken. What shifter is it. Sram, Shimano, Microshift, Campag and what model. If your really lucky it may be just the end of the cable coming away in the shifter.
    Too many bikes according to Mrs O.
  • MattFalleMattFalle Posts: 11,644
    Take the cable out to inspect as starters then have a good old nosey at shifter and caliper to see if anything is btoken

    After all, £3 for a new cable or catching dead disease, its a tricky decison.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • masjermasjer Posts: 2,361
    Hi
    when you say tightened / loosened the barrel adjuster are you sure you've turn it the correct direction? Tightening the brake cable is anticlockwise on the barrel adjuster (loosening direction for a bolt) and loosening is (predictably) clockwise.
  • buddhahatbuddhahat Posts: 16
    edited March 2021
    oxoman said:

    Doesn't sound to good to be honest, sounds like you over tensioned it and the internals have partially dislodged or broken. What shifter is it. Sram, Shimano, Microshift, Campag and what model. If your really lucky it may be just the end of the cable coming away in the shifter.

    Thanks for this. It’s a Shimano Sora Triple. What do I need to look for inside the shifter? I can’t see anything obviously broken but don’t really know what to look for!

  • buddhahatbuddhahat Posts: 16
    masjer said:

    Hi
    when you say tightened / loosened the barrel adjuster are you sure you've turn it the correct direction? Tightening the brake cable is anticlockwise on the barrel adjuster (loosening direction for a bolt) and loosening is (predictably) clockwise.

    I can’t remember which direction but I turned it so that the calliper was being pulled towards the barrel adjuster (shortening the cable) which I assumed was tightening. Is it possible to over tighten so that damage occurs within the shifters?

    Thanks,

    B

  • masjermasjer Posts: 2,361
    It sounds like you adjusted it correctly. Is the cable clamp bolt up tight enough? The cable could have possibly slipped.
  • buddhahatbuddhahat Posts: 16
    Yeah the pinch bolt was definitely tight enough. It’s weird - there was like a loud click and the shifter went completely slack so I assumed the cable was snapped but when I loosened the barrel adjuster on the brake, the shifter regained its tension but brake still didn’t function properly. I just wondered if this was a common fault but sounds like maybe not.
  • oxomanoxoman Posts: 11,738
    Its possible that the barrel on the end of the cable in the shifter has failed but is still hanging on to a few strands. Best bet is to have a look. If not sure what to do look on youtube park tools video clips.
    Too many bikes according to Mrs O.
  • masjermasjer Posts: 2,361
    There aren't many parts inside a shifter concerning the braking but I' d still check to see if anything is amiss . If all looks good, the problem must lie in the caliper. Check the activation arm operates freely. If it's sticking the shifter might go slack as described.
  • masjermasjer Posts: 2,361
    If the arm is sticking this might help https://singletrackworld.com/forum/topic/psa-trp-spyre-rebuild-guide/
  • buddhahatbuddhahat Posts: 16
    Thanks for all the advice guys - much appreciated.

    B
  • buddhahatbuddhahat Posts: 16
    edited March 2021
    I had another look at the brakes this evening.

    The Spyre C (mechanical disc brakes) has adjustable pad adjusters that allow you screw the brake pads in closer to the rotor to compensate for pad wear.

    As far as I can tell what seems to be happening is that when I depress the brake lever to push the pads to grip the rotor, these adjusters are retracting back into the housing i.e. they’re completely loose! I screw them back so that the pads are just shy of the rotor again, depress the lever and, hey presto, the pad adjusters are pushed back into the housing again. It’s almost as if they’ve been completely threaded.

    I wonder if this might be the cause of the loud clicking noise and sudden slackness in the lever I encountered today - that the pad adjusters suddenly went loose?!

    I saw a TRP video today which said you need to use thread lock to glue the adjusters in place which seems bonkers because I thought the whole point was that you could adjust them. But perhaps I need to glue them to avoid this slipping?

    Here’s a link to the video: https://youtu.be/CDYgQpmKiBs

    Does anybody have any experience with this scenario?!

    Edit: From reading the comments in the video it seems this could be my issue. I will try some thread lock in a couple of days and, if successful, will update this thread.

    Thanks again all for the input.
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