Disc rub on turns driving me crazy?- Mtbr.com
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  1. #1
    better than I deserve
    Reputation: roblee's Avatar
    Join Date
    Sep 2011

    Disc rub on turns driving me crazy?

    I have newer BB7 brakes with new Velocity Blunt rims and XT hubs on a Azonic aluminum DS-1 frame.I am able to set up the brakes easy to have no rub going straight and great stopping power with good lever action.I find I have to back off on the brakes adjustment to avoid the excessive rub on turns, still adequate but not as ideal of a set up.
    My problem is on any kind of turning I can hear that the disc rubs enough that I can hear it just touching.The harder I lean into a turn the louder it is.

    If the disc is attached to the hub which is attached to the axle that has no extra play because I checked and they are new there should not be that kind of movement.Is the frame flexing that much? It`s a beefy frame so I would not think it should flex that much? If the rim is weak titts then the movement would be from the spokes to the rim and not effect the brakes. I`m lost as to why this is so bad? I can still ride and enjoy the bike but it is an irritant to say the least.
    Last edited by roblee; 04-08-2012 at 01:52 PM.

  2. #2
    mtbr member
    Reputation: winter's Avatar
    Join Date
    Nov 2009
    As you stated, the frame is flexing, or the fork is flexing (if the rub is at the front brake). It could also be that the skewers are slightly loose and allowing the hub to shift slightly within the drop outs which then allows the discs to rub on the brake pads. It could be that the skewers are made of softer material (e.g. titanium), which also leads to the hub and rotor to shift slightly when under side loading forces.

    I wouldn't worry about a slight rub too much as long as the wheels are securely attached to the frame and the fork. However, I can understand the desire to get rid of the problem as it's quite a psychological drag and has more effect on the rider's psyche than the actual bike.
    Go on ahead, I'm gonna take a breather.

  3. #3
    mtbr member
    Join Date
    Oct 2008
    If your running standard QR skewers, try going to a 10mm thru or bolt on. Should stiffen the rear end up. That's what i went to on my Azonic Steelhead.

  4. #4
    Spanish rider
    Reputation: Pableras's Avatar
    Join Date
    Aug 2006
    Sorry man, but we live in a world where all structures experience a certain deformation under any load.

    Note that the disc runs very close to the pads, ad the loads applied to the frame can be quite high so the deformation experienced by the frame and the axle-frame joint usually leads to rubbing between the disc and one of the pads. I think 99% of the bikes out there experience this phenomenon.

    Also note that the axle is not completely bound to the dropout, the union has a certain flexibility which, as I said contributes to the overall deformation. Thigthening a little bit more the QR may stiffen this area...

    If you want to see how this happens just put the bike next to a wall and push the external pedal against the wall. You'll see that the (apart form the wheels, which experience substantial deformation but does not contrubute to the rub) the frame flexes a little to the point that there is no clearance between one of the pads and the rotor.

    Try to set the barkes to the maximun clearance that allowa you to brake properly, properly tighten the QR and try to ignore the noise
    A pessimist is an experienced optimist

  5. #5
    Trail Tire TV on blogger
    Reputation: thomllama's Avatar
    Join Date
    Oct 2007
    if it's just the front it may be the fork, but, I can almost guarantee it's your hubs. just One of the MANY reasons I dislike cup and cone style bearings on hubs. I had the same issue with XT hubs.

    The bearings in your hub are just that tad loose enough to shift under weight. they will flow/spin beautifully until you put twist weight on them. Then the cone will rock just that little bit which is multiplied by the distance of the brake rotor form the axle.

    you can play with the tension on the bearings but it's literally like 1/8 a turn difference on the cone. You can live with it, or you can replace the hubs with something better. I went to Hope hubs and the problem was solved.
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  6. #6
    mtbr member
    Reputation: akacoke's Avatar
    Join Date
    May 2011
    i had this problem with my bike too. just turned the knob on the bb7 back 1 click. went away
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  7. #7
    better than I deserve
    Reputation: roblee's Avatar
    Join Date
    Sep 2011
    Seems to be the rear only,I am using the XT skewers and they are really super tight never had any shifting in drop outs yet from them.The hub bearings are tight enough that I can not get any noticeable play from push-pulling on the wheel.I am about 190lbs.I guess just back off the adjustment and deal with it.At least it`s comforting to know it`s not uncommon. Thanks for the responses and help peoples.

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