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Old 07-22-10, 04:29 AM   #1
GBHEC
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Avid Juicy 3 - Vibration

I have the Canondale F5 with the Avid Juicy 3 brake system fitted to the bike front and rear. The bike is over a year old and hasnt been ridden hard just on the road for communiting in the summer months.

I have a problem with the rear brake whereby you get alot of vibration when the brake is applied. I have tried bleeding the brake and replacing the pads, i have also tried to align the caliper to the disc with the caliper bolts loose, squeezing the brakes and then retightening but the vibration is still there.

When the brake is gradually applied the vibration shakes the bike and isn't really effectiving slowing the bike until you get to the point where the wheel locks up. I have enough power in the brake to easily lock the wheel but i dont have any intermediate braking ability so they are either off or wheel is locked up.

Is anyone able to give me any ideas to what may be causing the problem?
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Old 07-22-10, 06:53 AM   #2
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tighten down your caliper and rotor fixing bolts to the recommended torque specs.
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Old 07-22-10, 12:26 PM   #3
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Thanks for your response Severian, I've checked the bolts and all look to be tighened correctly.

Would you have any more suggestions?
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Old 07-22-10, 03:58 PM   #4
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Check your rotor for runout(side to side movement).

Last edited by Booger1; 07-22-10 at 04:11 PM.
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Old 07-24-10, 06:19 AM   #5
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Hi Booger1,

When you say run out I assume you mean if the rotor is warped and not running in a true plan, if so what do you find is the best way to check the alignment of the rotor, by eye it looks ok but I'm not sure what tollerance the alignment should be?
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Old 07-24-10, 06:44 AM   #6
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Avid's commonly shudder like that. I would probably start by cleaning the rotor with brake cleaner (Kleenstreak works) and then sanding down the pads.
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Old 07-24-10, 08:16 AM   #7
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I had a weird noise/vibration with an Avid 'clean sweep' rotor. I replaced it with another brand, and now have no noise/vibration.
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Old 07-29-10, 02:13 PM   #8
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Hi Guys, many thanks for all your good comments, I just thought I'd let you know the outcome!

It seemed most people were suggesting the rotor so I took a closer look, I fired a plumb laser on the leading edge and gradually turned the wheel, the rotor was straight as a dye - or so i thought!!!

I then tried a gauge which measures to the 1000th of an inch and found that there was a bow in the rotor of 3000th of an inch (0.0762mm); I flexed it back into position so it was within 1000th of an inch (0.0254mm) across the total perimeter of the rotor.

Put the wheel back on and tested in out, not a vibration to be felt.

I am absolutely amazed that the rotor would have to be this accurate so no wonder every time I visually looked at it, it seemed in perfect alignment.

I am also amazed with how easy the rotor was to flex back into the right position so I'm now very paranoid about knocking the rotor and ending up with the same problem but for now it works perfectly.

Thanks again to you all for taking the time to comment.
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Old 07-30-10, 10:17 AM   #9
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A good rule of thumb for all brake rotors is .001 runout for every 1 inch of diameter,measured at the outer edge of the rotor.Anything more than that and you can start having issues with grabbing,noises,clicking from the pads jumping in the calipers and so on.
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