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Hope Brake Alignment Problem

CroptonboyCroptonboy Posts: 164
edited January 2019 in MTB workshop & tech
So when I press my front brake, the disk gets pushed from one side to the other. It was suggested that I could use shims to offset the calliper, but looking at my video below, any shimming is going to move the calliper in the wrong direction?

https://youtu.be/u6iEPRmChYg

As you can see, the disk is being moved from right to left because the pad on the right is already touching the disk. Any shims are going to move the calliper further left, so what's my solution, machine down the calliper mount so it's thinner?

Posts

  • whyamiherewhyamihere Posts: 7,397
    You can shim the rotor. Obviously just make sure you use the same size shim on each of the 6 bolts.
  • steve_sordysteve_sordy Posts: 2,124
    edited January 2019
    I put a business card between the rotor and the pad, then slacken the caliper mounting bolts. Apply the brake firmly and then tighten the caliper bolts steadily so as not to twist the caliper. Result is the whole caliper will have been moved over by the thickness of the business card.
  • The RookieThe Rookie Posts: 27,748
    edited January 2019
    The pistons aren't adjusting properly, its a caliper issue. the right hand piston/pad should be self adjusting out further so it doesn't do that.

    But you seem to have got it censored about face, if you space the caliper it will move it to the left so the right hand pad engages the disc earlier stopping the disc being pushed to the right, so shimming it will work.
  • The RookieThe Rookie Posts: 27,748
    I put a business card between the rotor and the pad, then slacken the caliper mounting bolts. Apply the brake firmly and then tightness the caliper bolts steadily so as not to twist the caliper. Result is the whole caliper will have been moved over by the thickness of the business card.

    Its IS mount not PM mount....oops.
  • The Rookie wrote:
    The pistons aren't adjusting properly, its a caliper issue. the right hand piston/pad should be self adjusting out further so it doesn't do that.

    But you seem to have got it ars* about face, if you space the caliper it will move it to the left so the right hand pad engages the disc earlier stopping the disc being pushed to the right, so shimming it will work.

    I think you might be right in that the piston's aren't adjusting themselves properly but it's the right hand piston (in the video, bike is upside down) that is too far out. RH Pad is already touching the disk and when pressing the lever, then pushes the disk to the left

    So if I move the calliper further left, the RH pad will push even further against the disk

    Might be a good shout shimming the rotor though!
  • The RookieThe Rookie Posts: 27,748
    Maybe I'm misreading the video, it looked like the disc moved towards the fork as you pulled on the brakes, but not seeing the lever its hard to say!
  • cobbacobba Posts: 282
    Are both pistons moving when you squeeze the brake lever?

    Looks like what would happen when there's a sticky piston.
  • steve_sordysteve_sordy Posts: 2,124
    The Rookie wrote:
    I put a business card between the rotor and the pad, then slacken the caliper mounting bolts. Apply the brake firmly and then tightness the caliper bolts steadily so as not to twist the caliper. Result is the whole caliper will have been moved over by the thickness of the business card.

    Its IS mount not PM mount....oops.

    How the hell did you spot that! The video clip is only 3 seconds long and it took me several views before I saw the caliper mount.

    Therefore you need another solution. Probably need to fix the sticky piston problem properly.
  • steve_sordysteve_sordy Posts: 2,124
    The Rookie wrote:
    How the hell did you spot that!
    Using the pause button......

    We are not worthy! :oops:
  • Your calliper should be aligned so the disc runs perfectly dead centre of the grooves in the calliper which from the vid yours looks pretty good. From what I can see it looks like you have a very sticky piston. Callipers need a service every now and then to keep the pistons sliding nice. I fully strip mine every few years and change the piston seals but more importantly every 6 months I remove the pads and apply hunters silicone grease to the pistons and cycle them in and out by pushing the pistons in and pumping the levers until they run smooth. Make sure you don't pump the pistons all the way as they can pop out and then you need to re bleed the calliper. Obviously clean them thouroughly after before installing the pads and also be careful to not damage the pistons.
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