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Thread: Need help diagnosing brake shudder please.

  1. #1
    Junior Member
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    Question Need help diagnosing brake shudder please.

    Hi Guys

    I am having an issue with brake shudder on my nc700 front brakes. I initially thought the brake disc was warped. So I bought a new disc and the shudder went away. For a few hundred km at least. Now it's back. As you can see on the attached photos there is strange patched discoloration on the old and the new disc. I took off the wheel and took it to a wheel repair center where they put it on a lathe and measured the disc with a dial gauge. They confirmed the the disc is not warped and running straight. I have also flushed the brake fluid and bled the brakes. This shudder has also continued across 2 pairs of brake pads. I am stumped as to what can be causing this. The bike will brake relatively smooth from high speed and once the speed gets around 30km/h the front will start shuddering. Anybody have any ideas?
    Attached Images Attached Images Need help diagnosing brake shudder please.-20190928_085543-jpg Need help diagnosing brake shudder please.-20191017_164250-jpg 

  2. #2
    Super Moderator Need help diagnosing brake shudder please. 670cc's Avatar
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    I noticed the pattern on the disk in the upper photo shows 5 discolored areas, coinciding roughly between the 5 bolt mounting locations. I’ve never heard of such a problem, so I’m just speculating wildly. Could this have something to do with the right wheel axle spacer or the mounting lugs for the brake caliper? Could the caliper somehow be severely offset from the plane of the disk? Does the wheel spin freely when the brake is not applied?
    Greg
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  3. #3
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    Yes it spins freely. I have looked at the caliper and cannot see anything wrong. If it was offset then it should be binding continuously if the disc is true. As I said, I am stumped.

  4. #4
    Senior Member HarveyM's Avatar
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    Just spitballing but Piston sticking? Causes the pads to be out of parallel when engaging. Less disc flex were the bolts are = more pressure, friction there. Bent wheel/ bad wheel bearings (wheel runout instead of disc runout)? Head bearings bad?

  5. #5
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    I am with Harvey.........on the caliper piston not retracting.......... causes, piston sticking in the caliper bore, caliper seal issue, brake master cylinder not releasing pressure. By the discoloration of the disk it appears the pads are dragging once your riding. (The caliper piston seal is responsible for the piston retraction )

    That discoloring looks like it’s getting really really HOT !!!!!!

    Stock brake lever ? Aftermarket lever might be holding the brake on ????
    Are the pads wearing evenly.......the caliper slides or floats on the caliper pins. Bent or stuck pins would cause the whole caliper to stick. Usually the piston pad wears more quickly and the one side of the rotor would show more heat or wear when compared to the other side.

    Ride the bike under normal conditions for several miles.......stop, place on center stand and immediately check to see if the front wheel spins without dragging.

    When the wheel was inspected and checked for runout ..........were wheel bearing were checked for smooth operation, no sticking or notchy feel, rust or sloppiness ?????????

    If debris blocks the compensating port in the master cylinder , brake pressure will trapped or held in the caliper causing drag only when your riding.

    Need help diagnosing brake shudder please.-e9f07b10-51ed-4834-bbe8-155b49f35abd-jpg
    Last edited by showkey; 17th October 2019 at 11:07.

  6. #6
    Senior Member Need help diagnosing brake shudder please. ld_rider's Avatar
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    I see two rotors and they are not the same. I would stick with an OEM part to eliminate one variable.
    Rob in New England
    IBA# 540

  7. #7
    Senior Member
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    Quote Originally Posted by ld_rider View Post
    I see two rotors and they are not the same. I would stick with an OEM part to eliminate one variable.
    My thoughts exactly.

    Also, sounds like the same exact problem another member was having on here. Was it Afan?

    About the only other variable you could change would be the caliper. Maybe like mentioned before there could he a piston not functioning properly causing uneven pressure on the rotor, possibly warping it?

    Or, maybe there is supposed to be a shim or something behind the back pad that isn't there anymore and like Greg mentioned, its causing more pressure on the outside than the inside, instead of even pressure on both sides, and this is causing you to be able to feel the 5 points around the rotor where it's mounted to the wheel.

    This would make sense as to why it went away when you got a new rotor put on then came back. A new rotor would he hard, but as you used it more, the heat could make the rotor a bit softer and able to move more in between the mounting points.

    Sent from my SM-G930V using Tapatalk

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