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  1. #1
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    weird noise FINALLY solved

    I'd put a set of Campy Neutrons on my BMC SLC01 Pro Machine.

    Started having noise EXACTLY like chain rub on the FD and in exactly the same way that happens - ie worse under load.

    So here's what I did:

    Adjusted FD several times.

    Changed cranksets.

    Changed FD.

    Changed pedals.

    Nothing helped.

    So put on a different rear wheel - Noise gone!

    Think the Neutron may have a hub problem (it's an old hub that I rebuilt).

    Pulled the hub apart and cleaned & oiled the pawls.

    Put Neutron back on the BMC - noise still there

    The I happen to spinning the wheel listening for the noise - and see the answer - zero clearance from the offset NDS spokes to the left chainstay

    It will just touch enough, and then the frame amplifies and changes the sound. And yes the wheel is in straight.



    I've been working on bikes for years now, and still come up against baffling noises. So kids remember that those asymmetric Neutrons may not work with all frames.
    There's sometimes a buggy.
    How many drivers does a buggy have?

    One.

    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.

    http://www.youtube.com/watch?v=GekiIMh4ZkM

  2. #2
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    Are the bearings still good? Maybe changing them will help if the bearing race isn't worn out. Or if I am seeing the picture correctly, the spokes are rubbing?

  3. #3
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    Bearings and rest of hub are like new. Neutrons have the spokes offset to the left on the rear wheel. No, the noise is the offset NDS spokes on the Neutron just touching the left chainstay which is quite curved inward on this frame type. And making a sound just like FD chain rub under load.
    There's sometimes a buggy.
    How many drivers does a buggy have?

    One.

    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.

    http://www.youtube.com/watch?v=GekiIMh4ZkM

  4. #4
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    I'm really impressed that the stays are curved inward enough to get anywhere near the spokes.

    As you point out, Neutrons may not work with frames with stays curved this much, nut the inverse is also true, owners of curved chainstay bikes have an extra point of clearance to worry about.

    Question re; the diagnostics, Did this rub all the time, or only when pedaling, and worse under load? If the former, you had a clue, since there isn't chain noise when coasting. If it only happens pedaling, especially under load then chainstay flex, and/or a trace of hub play could be factors. Check the hub for any bearing play, which is easy to resolve.

    If you want to use these wheels on that frame, consider adding a thin washer under the axles left end cap. 1mm might be enough to resolve the rub, and won't create any issues elsewhere. You could dish the wheel another 1/2mm to the left to compensate, but it probably isn't necessary.
    fb
    www.chain-l.com

    Solving any problem requires understanding the underlying cause

  5. #5
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    Thanks for the idea. Yes, the problem only showed when pedaling. The tiny amount of clearance disappeared when the bike is under load, and worst when standing. No pedal = no noise. Hence my misdiagnosis as it sounded exactly like the chain touching the FD with every pedal stroke. I'll double check the dish on the wheel. It runs straight, the spokes all feel good. Possibly the whole dish has shifted left.
    There's sometimes a buggy.
    How many drivers does a buggy have?

    One.

    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.

    http://www.youtube.com/watch?v=GekiIMh4ZkM

  6. #6
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    Quote Originally Posted by bikerjulio View Post
    Thanks for the idea. Yes, the problem only showed when pedaling. The tiny amount of clearance disappeared when the bike is under load, and worst when standing. No pedal = no noise. Hence my misdiagnosis as it sounded exactly like the chain touching the FD with every pedal stroke. I'll double check the dish on the wheel. It runs straight, the spokes all feel good. Possibly the whole dish has shifted left.
    Dish doesn't often (ever) change on a built wheel, and if it did, you'd notice that the rim is off to the left between the stays. But you can verify the dish by noting the rim's position, and installing the wheel cassette to left. The rim on a correctly dished wheel will end up in the same place. If it moves then yes you have a wheel dish issue. (be sure to install the wheel identically, preferably by holding the bike vertical on the floor and letting it find it's own place).

    The fact that it's load sensitive, indicates that flex is the issue, but take a minute to triple check that it isn't the entire hub shell shifting forward on the bearings.

    Campy hubs are super easy to adjust while on the left with the tight in the frame. You'll need a 2.5mm(?) allen key to loosen the left side dust cover, then tighten it by rotating the cover to the right, and lock back into place. Make sure the wheel has zero play at the hub, if in doubt a slightly tight hub is better than a loose one.

    Otherwise add the space and move on to more interesting problems.
    fb
    www.chain-l.com

    Solving any problem requires understanding the underlying cause

  7. #7
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    Quote Originally Posted by bikerjulio View Post
    Bearings and rest of hub are like new. Neutrons have the spokes offset to the left on the rear wheel. No, the noise is the offset NDS spokes on the Neutron just touching the left chainstay which is quite curved inward on this frame type. And making a sound just like FD chain rub under load.
    I just learned something new. I would have never guessed it. Thanks.

  8. #8
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    Checked the dish. The wheel is true and dish even to within less than 1mm.

    There's no play in the hub. When I put on a Ksyrium I've got about 5-6 mm of clearance with the NDS spokes.

    The NDS spokes on a Neutron are biased strongly to the left, and it's obviously not suitable on this frame.
    Last edited by bikerjulio; 03-24-2012 at 03:58 PM.
    There's sometimes a buggy.
    How many drivers does a buggy have?

    One.

    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.

    http://www.youtube.com/watch?v=GekiIMh4ZkM

  9. #9
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    Thanks.

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