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  1. #1
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    ML8 Frame Vibration from Rear Braking ?!?

    OK, here is my dilemma. Ever since switching from 160mm to 180mm disc on my rear brake (Shimano XT 775, using Shimano rotors), I am getting some crazy frame vibrations at hard braking....and I really mean crazy frame vibrations. I get the crazy high pitch squealing too, but that's just a nuisance in comparison to the vibrating frame during hard rear braking. It's so pronounced that it really affects the braking and suspension performance quality in the rear quite badly.

    Did some digging in the brake forum and tried the most common/obvious recommended remedies. Changed the pads from Galfer to my old Shimano sintered pads, still the same problem. Took all rear brake parts off/apart, cleaned them and re-installed, still same issue. In the meantime I noticed that monolink had developed some play and replaced all 4 monolink bearings (which really needed replacement after 2 years of duty). But nope, that wasn't the culprit either.

    Today, I took the 160mm Magura rotor off my hardtail and transferred it to the rear of my ML8 (can no longer use my Shimano 160 due too many mechanical warps...that's why I replaced it originally with a Shimano 180 coming from my DUC, which in turn got a 210 upgrade and works very nice on my DUC). I got this annoying high pitch squealing again, but at least the crazy vibration issue seems gone now....though I am still skeptical and will continue to monitor. Not to mention....I have no friggin' clue why this is happening.

    Did anyone else have this kind of problem on their ML8 or anyone with any advice that will allow me to use my 180 rotor in the rear (which worked perfectly on the front)??

  2. #2
    Schipperkes are cool.
    Reputation: banks's Avatar
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    Your post is hard to read.

    1. Do not mix different manufacturer rotors & brake calipers. Rotors are different thickness and can cause a whole lots of problems; the shape of the caliper & pads are designed with the rotor.
    2. Are all of the brake parts correctly torqued? Hard anno frame?
    3. What brand of QR? If it's a external cam version, Salsa/WTB, switch it out for an Internal cam version-Shimano and make sure it's Tight!
    4. Have you tried the Organic pads? Metallic/Sintered pads are harder, have a lot more metal in them and are a sure-fire way to make brakes audible.
    5. When you put a 7"/180mm rotor on the back, your brake caliper to rotor leverage changed and can cause a handful of problems. I'm 230lbs and find the 7" rotor in the rear has too much 'power' and end up skidding all over the trail; same on the ML8 and 29" wheel hardtail
    Quote Originally Posted by mikesee
    Better suited to non-aggressive 125# gals named Russell.

  3. #3
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    Hi Banks see my remarks below in red...

    Quote Originally Posted by banks
    Your post is hard to read.

    1. Do not mix different manufacturer rotors & brake calipers. Rotors are different thickness and can cause a whole lots of problems; the shape of the caliper & pads are designed with the rotor.

    Yup, you're probably right, but my Magura Marta rotor was the only 160mm rotor I had lying around, since my Shimano 160 is badly warped and unusable.

    2. Are all of the brake parts correctly torqued? Hard anno frame?

    Definitely correctly torqued using torque wrench and torque ratings from the brake manual. And my torque wrench is not a cheapy model either...paid around $100 for that thing.

    Yes, Hard Ano frame
    .

    3. What brand of QR? If it's a external cam version, Salsa/WTB, switch it out for an Internal cam version-Shimano and make sure it's Tight!

    Am using DT Swiss RWS and it is super duper tight!!

    4. Have you tried the Organic pads? Metallic/Sintered pads are harder, have a lot more metal in them and are a sure-fire way to make brakes audible.

    Have not tried organic pads yet. My Shimano as well as Galfer pads are both sintered pads. The Galfer pads are actually not very audible in conjunction with Shimano rotors, but I digress. Good point about the organic/resin pad, will try and go back to OEM resin pads from Shimano to see if that will remedy the vibration issue (the resin pads wear really quickly though).

    5. When you put a 7"/180mm rotor on the back, your brake caliper to rotor leverage changed and can cause a handful of problems. I'm 230lbs and find the 7" rotor in the rear has too much 'power' and end up skidding all over the trail; same on the ML8 and 29" wheel hardtail

    Hmm, I guess we all have different experiences. I went from 160 to 180 rotor in the back to combat hand fatigue on long descents (i.e. Downieville). I will admit though, the 160 is fine for the trails at home (Bay Area).

  4. #4
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    Quote Originally Posted by banks
    4. Have you tried the Organic pads? Metallic/Sintered pads are harder, have a lot more metal in them and are a sure-fire way to make brakes audible.
    Finally got around to buy organic pads and run them in rear for 3 rides over the last few days. Looks like Banks got it right....the frame vibrations as well as high pitch noise are completely gone, even after re-slapping my 7" Shimano rotor on the rear of my ML8. Nice

  5. #5
    Schipperkes are cool.
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    wooHOO! Brake resonance suxs.
    Quote Originally Posted by mikesee
    Better suited to non-aggressive 125# gals named Russell.

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