slightly warped rotor-
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  1. #1
    mtbr member
    Join Date
    Nov 2009

    slightly warped rotor

    I just bought a scott scale. I love the bike, but i do hear that slight "ziiiinnnnngggg" of the rotor rubbing when I spin the rear wheel off of the ground. Will this extra drag hurt performance or is it just something that I shouldn't worry about too much. How much does this affect performance? Is it a big deal? thanks.

  2. #2
    Old man on a bike
    Reputation: Bikinfoolferlife's Avatar
    Join Date
    Feb 2004
    It's not a big deal, it happens; not a big deal in terms of soaking up your energy. When it starts to make noise I true it; I use a small adjustable wrench with the jaws close around the rotor and gently bend back the high spots using the caliper as a guide.
    "...the people get the government they deserve..."
    suum quique

  3. #3
    Reputation: XSL_WiLL's Avatar
    Join Date
    Nov 2004
    Well if it doesn't considerably slow the revolution of the wheel, it likely will not have a notable affect on performance.

    All rotors come slightly out of true.

    If they're hydraulic brakes, you may be able to remedy your problems by simple re-centering the caliper.

    If they're mechanical brakes, recentering the caliper may help as well. Or you can see which pad is touching the rotor and dial out the offending pad a little bit.

    Or... you can see where the rotor is hitting the pad, and then pull it in the opposite direction to true it. This can be done with an adjustable wrench, or even just your fingers. Wipe down the rotor with alcohol afterward to remove oil from your fingers.

  4. #4
    Reputation: XSL_WiLL's Avatar
    Join Date
    Nov 2004
    If you look at the disc brake FAQ (link in the upper right hand corner of the page)

    What can I do with warped rotors?

    There are NO rotors that are dead flat and they can all be trued up - even most new ones. As rotors are a thin stamped steel product they all tend to be somewhat warped - some more or less than others. But warpage is curable so don't freak out. Warpage that causes brake drag or "zinnnggggg" needs to be fixed and luckily that's quite easy. I true up ALL my rotors and can usually do them in two minutes. They don't have to be dead-on but just fairly close. Grab a small clean adjustable wrench and a piece of something white. There are also special tools for the job on the market; the best ones come in a set of three.

    Truing the rotors - Make sure you have lots of light so you can see well. Lay the piece of white paper or plastic below the bike on the floor. Now stand where you can look through the caliper and reposition the paper on the floor so the white background is visible through the caliper when viewed between rotor and pad. The light colored background lets you see what the rotor is doing inside the caliper when you spin the wheel.

    When you're all set up, slowly spin the wheel and look for spots on the rotor which are out of true and touch a pad on one side or the other. When you find a spot which rubs or nearly rubs, rotate the rotor back out of the caliper 90 - 180 degrees, place the clean adjustable wrench on the rotor with the jaws just open wide enough to grasp the rotor, and verrrrry gently bend the rotor in the opposite direction.

    A little movement goes a very long way here. Apply the brake lever after every pry to re-set any pad that has got squished back. Don't tweak hard or you will make things worse than they were. Don't forget - more is NOT better! Keep doing this until the rotor runs fairly straight and you can see and hear that it is not hitting the pads.

    This is normally a quick job but I'll admit some have taken me a 1/2 hr or so to true. There are specific tools out there that make the job easy. One company markets a set of three tools - to be used together to isolate the warp. That same company even markets a trail tool that allows you to true warped and tweaked rotors trailside so that you don't get your sweaty, greasy fingers on the rotor. If you touch the rotor with fingers then clean it with isopropyl alcohol before you ride. Any oil or grease, yes even body oils, is not a good thing. The next best cleaning fluids are Windex or a light dish soap. Washing the rotors at bike wash time is not a problem.

    There are good reasons for wanting true rotors. They are -
    1. Prevent premature pad wear.
    2. Prevent uneven, inconsistent rotor wear. Consistent rotor wear = consistent braking.
    3. Eliminate pre-heating the calipers and fluid.
    4. Eliminate the irritating noise factor.

  5. #5
    2010 RockHopper Comp Disc
    Join Date
    Aug 2009
    I use both a 6" and 10" crescent wrench that I cover in either duct or gorilla tape at the points where it will touch the rotor. Simply eye the rotor as it revolves and when you see the location of the bend, mark it with your eye and attached the wrench tightening it down. Then you want to pull to the opposite direction and hold it in that position for a few seconds. Sometimes this method works, other times it doesn't and the rotor will just fling back into its untrue state.

  6. #6
    mtbr member
    Join Date
    Mar 2009
    NOT EVEN necessary; the use of adjustable wrenches.
    a simple light push of your thumb on the warped area is all that's needed.

    Try it, you'll see.....

    Cleaning off the oils from your thumb is a good thing too.
    "The older I get, the faster I was"

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