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  1. #1
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    Avid BB5 out of true when I'm on the bike

    My front disc is perfectly lined up between the pads when I am not on the bike, and spin the front wheel etc. But when I get on the bike, and especially when I turn, an angle gets introduced and the rotor rubs slightly against the pad - very annoying.

    These are my first disc brakes and were not installed by me, but it would be a hassle to go see the guy who did now. I can't get my head round what could be flexing between the forks, wheel and brakes to cause this. Any ideas?
    SPD shoes, pedals, cleats and the experience of going clipless. (a work in progress - let me know if I missed something!)

  2. #2
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    Reputation: Bikinfoolferlife's Avatar
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    Some forks flex enough to do that...perhaps your hub needs adjustment if there's some play in the bearings.
    "...the people get the government they deserve..."
    suum quique

  3. #3
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    Now you mention it, the spokes seem to be flexing enough to produce this effect... Doesn't seem right, but I'm even less knowledgeable about spokes than about disc brakes. The spokes shouldn't flex that much, surely? Esp. in one direction.
    SPD shoes, pedals, cleats and the experience of going clipless. (a work in progress - let me know if I missed something!)

  4. #4
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    Sounds like your wheel needs some maintenance.

  5. #5
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    I sometimes have the same problem when cornering hard on my BB7's. I actually think its my fork (stock low end fork on Hardrock). Reason I think its my fork is because my wheelset is brand new. But, I guess its always possible that its the rims......

  6. #6
    rebmem rbtm
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    Quote Originally Posted by blkss
    I sometimes have the same problem when cornering hard on my BB7's. I actually think its my fork (stock low end fork on Hardrock). Reason I think its my fork is because my wheelset is brand new. But, I guess its always possible that its the rims......
    I could see a fork making this problem during cornering if one leg was stiffer than the other, it wouldn't take much flex in the fork to make the pads rub if they are close to the rotor.

  7. #7
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    Quote Originally Posted by markowe
    Now you mention it, the spokes seem to be flexing enough to produce this effect... Doesn't seem right, but I'm even less knowledgeable about spokes than about disc brakes. The spokes shouldn't flex that much, surely? Esp. in one direction.
    It's not the spokes, the disc is attached at the hub, so perhaps if your hub flexed (unlikely) or needs adjustment (is there play?). Fork much more likely to cause this; I have had forks that do this. It's not a great big deal but make sure that your caliper is properly adjusted in relation to the disc as well or move your pads slightly out so that you avoid the rub...

    ps About that title, is your rotor actually out of true or not? It wouldn't matter if you were riding or not, it's either out of true or it's not...
    "...the people get the government they deserve..."
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  8. #8
    Out there
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    Make sure your QR is tight enough and the wheel is slotted fully in the fork.
    All problems in mountain biking can be solved by going faster, except the ones that are caused by going too fast.

  9. #9
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    I too just bought a new bike that came with BB5s and I had a slight rub at first as well. The problem was that the rotor came just slightly out of true, once fully broken in and adjusted I haven't noticed it come back.
    Also, I'll second about making sure your wheel is fully seated when tightening the QR's, a sometime source of mysterious come and go issues.

  10. #10
    Suffers From Binge Biking
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    It's a problem with your fork, not the brakes. I have BB7s on my bike mounted up to a Dart 2 fork. When it's rolling straight, there is no rub, but in turns the fork flexes enough to allow the rotor to rub. It used to annoy me, but realized the only way to fix it was to move the pads away from the rotor or buy a stiffer fork. So I don't even worry about it anymore.
    If it ain't broke, fix it 'till it is.

  11. #11
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    I've left it with the LBS - the fix-it guy reckons the brakes were never set up right so he's going to have a look. Still not sure exactly how that could be causing that effect. But he's also one of the top MTBers in my country, so I guess I trust him (unless he's planning to nobble my bike, ha ha)!

    Thanks for all the suggestions - quite a range there, I knew I was getting into more complicated ground as soon as I went disc, but there you go... They still work waaaay better than the Vs on my old Scott - I rode it today while the main bike is being sorted and it seems to take forever to come to a stop!
    SPD shoes, pedals, cleats and the experience of going clipless. (a work in progress - let me know if I missed something!)

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