front brake

chatlow
chatlow Posts: 850
edited May 2013 in Workshop
i have a problem with a brand new shimano r451 dual pivot brake.

it's been fitted correctly and the pads line up well. after the first ride the brake had slightly moved and the left pad was against the rim of the wheel. After adjusting it back to a square fit and the bolt holding in place tightened to the max i have cycled back from work and it's moved again. i can't screw it any tighter so how is it moving?! or have i fitted it incorrectly? or faulty?

thanks

Comments

  • maringirl
    maringirl Posts: 195
    There should be a small screw on top of the brake mech - maybe allen headed or maybe cross head screw driver type. Use this to centre brake properly.
  • wishitwasallflat
    wishitwasallflat Posts: 2,927
    I had this problem with a rear brake and it turned out the outer cable was too short and entering the brake at an angle - maybe worth checking it that's the problem/did you re-cable when fitting the new brake?
  • chatlow
    chatlow Posts: 850
    thanks. will check the cable on my lunch. I used the existing cable as it's in good condition.

    I don't really understand the concept of the 'centering' screw because I always tighten up the break and then squeezed the brake on fully and finish tightening them up to get it centered. Will have a look at the screw anyway. thanks
  • chatlow
    chatlow Posts: 850
    right just had another look and it seems the issue is that no matter how tight I set the main brake bolt to the bike, I am able to move the brake slightly left or right. That means that whenever i go over a curb or a bit of rough road it's moving my entire brake off its center.

    Any suggestions??
  • keef66
    keef66 Posts: 13,123
    Are we talking about the tubular type hex socket nut that goes through the fork crown from the rear? It's possible it's bottoming out on the bolt threads before it's clamping the caliper tightly to the fork. Maybe you just need a shorter nut?
  • chatlow
    chatlow Posts: 850
    yeah, that's the one. I tried adding another washer to the front of where it bolts on but still the same to so may try a shorter tube bolt later on and see if that helps

    thanks
  • keef66
    keef66 Posts: 13,123
    Or maybe the mounting bolt is tight enough but the locknut needs tightening to stop the caliper rotating on the mounting bolt?

    Look at the exploded diagram on Shimano tech docs

    http://techdocs.shimano.com/media/techd ... 625612.pdf
  • chatlow
    chatlow Posts: 850
    keef66 wrote:
    Or maybe the mounting bolt is tight enough but the locknut needs tightening to stop the caliper rotating on the mounting bolt?

    Look at the exploded diagram on Shimano tech docs

    http://techdocs.shimano.com/media/techd ... 625612.pdf


    Ahh, that's a great shout. Will take it all apart and see if that lock nut is tight and post my results later

    thanks!
  • chatlow
    chatlow Posts: 850
    unfortunately that nut was tight so im just about to fit the shorter tube nut that came with the brake

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