Front disc rubbing.

Phillw454
Phillw454 Posts: 101
edited June 2011 in MTB workshop & tech
Hello,
As per title, my front disc brake is rubbing quite badly and when the wheel is turnt freely with no resistance (Bike off the ground, upside down, whatever) it will only do about 5 or 6 turns before stopping (At a guess).

I have Avid Code 5 brakes. Apart from this they work fine front and back, very sharp.

How do I stop this? Is it a case of taking off the wheel and pushing back the pads slightly? I can't see any obvious way of adjusting the pads.

Thanks.

Comments

  • nicklouse
    nicklouse Posts: 50,675
    rubbing one side or both?

    recenter the caliper.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Phillw454
    Phillw454 Posts: 101
    How would I recenter it? Would it be on the Sram brake set up?

    I have had a brisk look over bout couldn't see anything obvious. Ill give it a real read through this evening.

    As for rubbing either side, I could not say sorry, I guess having the bike upside down and turning the wheel and seeing if it catches either side is the obvious way to tell?
  • JamieRa
    JamieRa Posts: 82
    loosen the 2 bolts that attach the Caliper to the Mount, apply the brakes, tighten the bolts while the brakes are applied and it should recenter.
  • Phillw454
    Phillw454 Posts: 101
    Awesome thanks a lot ill give it a go tomorrow.
  • Phillw454
    Phillw454 Posts: 101
    I have followed the advice and recenter'd the front caliper, while it is slightly better the disc still rubs and stops the wheel after only a few rotations.

    I have followed the advice in the Sram book about *Truing* the caliper which is more or less the same as centering it.

    Do I need to try and push the pad's back a bit? Is there an easy way to do this? Thanks.
  • nicklouse
    nicklouse Posts: 50,675
    so now go and let the pads bed in again.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Phillw454
    Phillw454 Posts: 101
    By bed in again I assume you ment go for a ride?

    I went for a quick 8 mile ride, nothing exciting, after getting home I noticed it was worse if anything. Standing over the bike and pushing the wheel with no load I'll get about 1-1.5 turns.

    I saw on youtube about a pad spacer? Is it not I should try pushing back the pads? I can now hear them rubbing the disc also.

    Maybe a case of too much fluid in the system?

    Sorry Just trying to get this sorted. Would pictures be any use if I uploaded some?

    If it matters I have the same rear brake and it is perfect.
  • RupertCommunicator
    RupertCommunicator Posts: 734
    It could be a few things:

    1. Bent disc. Spin the wheel and look at where the disc is rubbing on the pads. If the disc moves side to side in the caliper your disc needs truing. This can be achieved a few ways. Hammer + flat surface if it's REALLY bent, fine tuning is done with an adjustable spanner VERY gently. If it's only a tiny bit bent, I sometimes hit it or pull it with my hand using kitchen roll to stop getting finger grease on them.

    2. Caliper pistons have migrated inwards too much or unevenly. As the pads wear down, the pistons move in to keep the pads the same distance from the disc. As your caliper gets dirty/old the pistons can get stuck in when applied. This causes uneven pad spacing which can lead either to rub or only one pad moving. Remove your pads and push the pistons back in using a screwdriver or other poking device. You can also move them out as long as you are careful. DO NOT pull the levers all the way in with the pads out!! This will cause a piston to pop out and spill fluid everywhere. I have done it. It is very bad. Normally I try and give the inside of the caliper a clean and if the pistons are sticky, you can even try and work some lube it them. Just be aware that you will need to meticulously clean up afterwards to ensure that no lube is hanging around inside the caliper waiting to contaminate your pads.

    3. As far a spacing the pads go, you could just bodge it and tape a penny or something thinner if required either side of your rotor before fitting the wheel and giving the lever a good old pull to set the width.

    Experiment! That is the best. I'm sure there are proper mechanics who do things other ways or would frown on what I do, but this is what works for me. :D
  • captainfly
    captainfly Posts: 1,001
    First of all check the whee is set properly in the dropouts.
    Code calipers can be a bit difficult to line up, they are a bit more by feel than by the book, firt thing is to push the pads back into the caliper, eith with the pad spacer (piece of red platic that you put in when the wheel is out) but if you don't have one a arge clean flat blade screw driver will do. then with the caliper loose on the mount with the wheel in, is lightly pull and release the brake lever repetedly whllst tightening the bolts, a soon as they become lighly finger tight pull and hold the lever firmly and tighten the bolts so the caliper doesn't move. Now spin the wheel and listen for rubbing, then after hearing any rub rotate and feel the resistance slacken off the bolts at this place and then pull the lever and tighten to full torque setting, it's how I do mine. If you can't get rid of the rub. then you disk may not be true, take it off and put it on a flat surface or use a ruler, there are plenty of guides to true a rotor.
    -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
    Mongoose Teocali
    Giant STP0

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  • Phillw454
    Phillw454 Posts: 101
    I think the disc did have a very small bend in it hardly noticeable but I take it off and try truing it.

    I'll give the rest of it ago^^

    Thanks for the advice.

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