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  1. #1
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    Shimano BR-M446 Hydraulic Disc brakes question.

    I just bought a new 2012 Cannondale SL3 today and its my first experience with hydraulic disc brakes or disc brakes on a bike in general.

    The bike is pretty much brand new and the brakes stop great and appear to be working fine, but when they are letting off a very loud and nasty shreaking sound if i dont press them down all the way while the wheels are spinning.

    Is this normal? Can this be fixed? I just dont want to be making loud shreaking brake noises as i ride through the trails.

    Any help would be appreciated. thanks!
    Last edited by colehasarsx; 04-05-2013 at 08:02 PM.

  2. #2
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    These are the brakes that came stock on my bike as well. All I can say is that you need to bed them in during the break in process. If you just jumped on your bike and started riding it they will talk to you loudly. You need to clean them with some disc brake cleaner from an auto part store and then re-bed them. These brakes are not that bad, they are the lowest hydro brakes that Shimano make. I got the upgrade bug and bought a set of M785's with RT86's and they are night and day better. However, these M446's will work nicely if broken in correctly.

    Mark
    2012 XXL Carve Expert

  3. #3
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    Ok so I should google how to re bed hydro disc brakes?

    Aswell as getting disc brake cleaner and cleaning the discs with it? Thanks for the tip.

    I was just assuming that they weren't broken in yet and would eventually stop shreaking

  4. #4
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    Sorry, there are many posts about bedding in your brakes and I assumed you had read them. You need to (post cleaning) go about 15mph and slow to about 7mph, do not stop. Do this about 10-15 times. This will spread your pad compound around your rotors. and set a base layer of organic goo on your rotors. This will help with noise because you get vibrations (noise) when your pads slide over goo covered parts of you rotor and non goo covered parts. Once you have done this, you need another 10 or so stops from 15+mph to hard stop. This will bed your pads into to your rotor by cementing the goo you applied onto your rotors. Your LBS should have covered this with you when you bought your bike. Cleaning your rotors will help this process but it is not a game changer if you do not have the cleaner and need to ride.

    Mark
    2012 XXL Carve Expert

  5. #5
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    Can't fork and frame flex contribute somewhat too?
    Warped rotors, improperly tightened bolts,misaligned brake set-up too?
    Hey...check everything.
    MTB Disk Brake noise??? - Yahoo! UK & Ireland Answers
    roccowt.
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  6. #6
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    Quote Originally Posted by millertm View Post
    Sorry, there are many posts about bedding in your brakes and I assumed you had read them. You need to (post cleaning) go about 15mph and slow to about 7mph, do not stop. Do this about 10-15 times. This will spread your pad compound around your rotors. and set a base layer of organic goo on your rotors. This will help with noise because you get vibrations (noise) when your pads slide over goo covered parts of you rotor and non goo covered parts. Once you have done this, you need another 10 or so stops from 15+mph to hard stop. This will bed your pads into to your rotor by cementing the goo you applied onto your rotors. Your LBS should have covered this with you when you bought your bike. Cleaning your rotors will help this process but it is not a game changer if you do not have the cleaner and need to ride.

    Mark
    Ok awesome. i spend a good bit of time googling brake maintenance but i could only find bleeding them and changing the pads. I never found anything about bedding them.

    The bike is new but i got it from a dude who rode it twice and then didnt want to ride it anymore. But he bought it from my LBS so i didnt get that info. Im assuming i can get Disc brake cleaner from my LBS?

  7. #7
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    Quote Originally Posted by zarr View Post
    Can't fork and frame flex contribute somewhat too?
    Warped rotors, improperly tightened bolts,misaligned brake set-up too?
    Hey...check everything.
    MTB Disk Brake noise??? - Yahoo! UK & Ireland Answers
    What Millertm said makes a bit more sense because the bike has hardly been used yet so it wouldnt make sense for it to have flex or warped rotors.

    but if bedding the rotors does not fix it then one of the things you mentioned could be the problem and i will have to troubleshoot it further

  8. #8
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    Yea, it all is new it should be a bedding issue. Disc brake cleaner is found at your auto part store for about $2-3. I do not think that the LBS has it. Be careful when using it. Spray a bit onto a clean rag or paper towel then clean the rotor. If you spray it on the rotor it could drip onto you tires or rims. This stuff will eat rubber and remove paint like a champ.

    Mark
    2012 XXL Carve Expert

  9. #9
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    LBS should have a cleaner that works fine too. My LBS uses clean streak, I think.

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