1. The most important thing about buying a new bike is to make sure it fits. The only way you'll know if the bike is right for you is to size up the bike and make sure that the bike's geometry matches your body's geometry. Ask questions and do some research.
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2. If possible, try to find a shop that will let you demo the bike on real dirt. Five minutes in a parking lot won't cut it. You wouldn't buy a car without a real world test drive, and a bike should be no different.
3. Don't belive the hype. Just because your favorite rider or best friend rides a certain bike, that doesn't mean that's the best one for you. Have an open mind and be realistic about your needs and ability.
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  1. #1
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    Help...new to disc brakes.

    I have been riding and working on bikes for a while, but just picked up a used 2008 Stumpjumper Comp Hardtail , so I am a noob to some of the components. Two issues that I need some advice on:
    1. I have zero experience with disc brakes, and this has Avid Juicy 5s. There is some rubbing in the rear caliper. From reading other posts on here, I know that this isn't uncommon on these brakes. What's the best approach to resolving this?
    2. It has a fairly new XT bottom bracket that feels like it has an unusual amount of friction when spinning the cranks forwards or backwards, at least compared to my old one. Any advice on improving this or is the next step replacing the bottom bracket?
    Thanks for any help.

  2. #2
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    1. true the rotor and check to see that the pads are seated firmly.

    2. take it out and clean it, if it's clean there is a break-in period for the bearings. I wouldn't think so but check the bb shell width and installation instructions for the bb and crankset. Perhaps there is an additional plastic ring that results in too much pressure from the crank arm on the bearings. I'm assuming the crankset is a thru axle style. As long as it's not a creaking, popping hard rubbing gritty movement, it probably just needs some riding.
    No fuss with the MUSS

  3. #3
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    Thanks very much for the information. I'll carefully dig into the brakes like you suggested. It's a good chance to get to know my new bike before temperatures rise a bit.

    I can feel the friction in the bottom bracket, but definitely no off-axis movement, roughness, or noise. I'll try just exercising it a bit first.

    Thanks again!

  4. #4
    local trails rider
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    If the brake rubs consistently all around the circle, it could be a simple misalignment in the calliper. Usually that can be corrected by loosening the 2 bolts that hold the calliper to the adapter (that is fixed to the frame), squzzing and holding the brake lever, and retightening the bolts (while holding the lever).

    That doesn't quite always work, and then you may have to go for other ways to align the calliper with the rotor.

    Just having your quick release/axle seated a little different, or at a different tension can lead to a misalignment too, so actually checking your quick release might be the first thing to try with the brake.

    "it IS possible that you are faster or slower than anybody else who is having at least as much if not more or less fun"

  5. #5
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    Disc brake adjustments aren't difficult to do. But they require attention to detail and can be tedious. Avid brakes have these hemispherical washer stacks (CPS washers) that provide a lot of capability for adjustment, but also increase the tedium factor. The basic idea is that you want the rotor centered equally between the pads. There are a few techniques to get this result and you might need to try one or more to get it right.

    My Shimano bb's with external bearing cups have a lot of seal drag compared to the older bb types (square taper, octalink, etc). As long as the bb is smooth and quiet, I wouldn't worry.

  6. #6
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    Thanks very much for the detailed information. I'll leave the bb alone for now and work with the brakes. This site is a wealth of knowledge.

  7. #7
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    Quote Originally Posted by NateHawk View Post
    The basic idea is that you want the rotor centered equally between the pads.
    I thought you wanted the rotor closer to the piston side and not the fixed side, although that is the recommendation for the bb7s. Is this different for hydraulic? Please educate me.
    No fuss with the MUSS

  8. #8
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    Hydraulics don't have a fixed side, both move.

  9. #9
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    Then yes, rotor to the middle please.
    No fuss with the MUSS

  10. #10
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    Quote Originally Posted by canker View Post
    Hydraulics don't have a fixed side, both move.
    some cheap hydros have a fixed side...or at least had. I haven't seen any of those on the market for probably 8-10yrs, but they probably still exist. but yeah, any halfway respectable hydro has dual pistons.

  11. #11
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    If the wheel spins freely and you can just hear it rub once around for a quick zzzt then you may just not want to not worry about it. Yes, you can probably fix it by truing the rotor and/or adjusting the caliper but the fix probably won't last very long. As long as the wheel spins freely I don't consider it worth fixing.

    If the wheel gets noticeably slowed down then a fix is in order as described by others.

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