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Discussion Starter · #1 ·
Howdy, i've got Hayes HFX9 HD discs running 8" rotors on my Orange SubZero


The front runs perfectly, but i've got a really annoying and loud vibration coming from the rear. I've looked at the alignment of the rotor and caliper and it appears to be about .5mm out. Is this enough to vibrate?

Apart from that, all i can think it could be is a sticky piston as i don't reckon contaminated pads would do this.

Any one got any ideas and how to fix it?
 

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same problem with Magura Julie 2005

Hi,

I have the same problem.

I've just installed a almost new Magura Julie on my bike (rear) and it vibrates before the point when the wheel completely stops.

One more question. When the bike is stoped and the brake pressed, if I move the bike back and forth I can see how the pads are moving inside the calipper. Is it normal that the pads to move in the calipper?

Thanks again for your input.
 

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I'm taking it for granted that you know how to align the caliper on the rotor... :)

.5 of a mm isnt a lot..so that should be ok. Is the rotor true? Not warped?

Are you sure that the vibes are coming from the brake?

Can you hear any sounds like pad/rotor rubbing when you spin the rear wheel?

Have you checked all your bolts for tightness and torqued them with a torque wrench?

It *may* be a sticky piston, can you have a look?


R.
 

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Discussion Starter · #5 ·
checked them...

Rainman said:
I'm taking it for granted that you know how to align the caliper on the rotor... :)

.5 of a mm isnt a lot..so that should be ok. Is the rotor true? Not warped?

Are you sure that the vibes are coming from the brake?

Can you hear any sounds like pad/rotor rubbing when you spin the rear wheel?

Have you checked all your bolts for tightness and torqued them with a torque wrench?

It *may* be a sticky piston, can you have a look?

R.
Pretty sure the rotor isn't warped as when the wheel rotates there is no rubbing what so ever between rotor and pads. The pistons appear to be moving freely and i've tried diffirent methods of aligning the rotors with the caliper. I've done it by sight, i've loosened the bolts and applied pressure to the brake lever to centre the rotor with the pads and then tightened the bolts securely. Each time, i still get the vibrations.

Only thing i've not done is use a torque wrench, but would this really cause any vibrating problems?

thanks for the help on this.
 

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When you apply the brakes, does the lever feel 'spongy'? If so, it may be you have air in the line and need to bleed the system.

Also, when applying the brakes, do you see the pads move approximately an equal distance to the rotor, and do they release the rotor and return normally again?

If it isn't any of these, then you have me stumped.

Are you sure that its the brake which is causing the vibrations, and not something else in the rear end?

R.
 

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shoogly said:
Pretty sure the rotor isn't warped as when the wheel rotates there is no rubbing what so ever between rotor and pads. The pistons appear to be moving freely and i've tried diffirent methods of aligning the rotors with the caliper. I've done it by sight, i've loosened the bolts and applied pressure to the brake lever to centre the rotor with the pads and then tightened the bolts securely. Each time, i still get the vibrations.

Only thing i've not done is use a torque wrench, but would this really cause any vibrating problems?

thanks for the help on this.
Shoogly - As you've probably come to realize....disc brakes are great, but sounds and vibrations aren't uncommon and can be VERY difficult to track down. Since you've tried most of the standard cures, have you also trued your wheels and verified that the spoke tension is fairly even? The tolerances on these things is very tight, and anything out of alignment could negatively effect them. Good luck. - Dave
 

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Discussion Starter · #8 ·
cheers for the tips...

but to no avail!

The bike's only a couple of months old so is probably due it's first service (i've ridden it a lot since i got it). It's definitely the brakes causing the vibration as it's only when i use them that it happens. I'll try trueing the wheel and see if that helps.

Cheers, Shoogly.
 

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Wheel truing effects disc brakes?

dnpeters said:
Shoogly - As you've probably come to realize....disc brakes are great, but sounds and vibrations aren't uncommon and can be VERY difficult to track down. Since you've tried most of the standard cures, have you also trued your wheels and verified that the spoke tension is fairly even? The tolerances on these things is very tight, and anything out of alignment could negatively effect them. Good luck. - Dave
Just got a set of Hayes with my new Paragon and I'm experiencing some hum from the brakes. I'm new to the whole disc brake thing so figured I'd check out the brake forum and see if there were any helpful hints. The question I've got is how does the spoke tension/truing effect the brakes? I thought that was one of the advantages of discs to begin with. Not trying to sharpshoot anybody.. I just reread my post and figured it might be taken that way.. Oops.. Just trying to learn all I can about these new fangled contraptions...
 

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ravegun said:
Hi,

I have the same problem.

I've just installed a almost new Magura Julie on my bike (rear) and it vibrates before the point when the wheel completely stops.

One more question. When the bike is stoped and the brake pressed, if I move the bike back and forth I can see how the pads are moving inside the calipper. Is it normal that the pads to move in the calipper?

Thanks again for your input.
Yes, it's normal. The wheel only moves in one direction when you're riding so it doesn't affects performace of the brake.

Spoke tension is relevant to disc wheels as an improper tension can cause any small vibration to resonate and consequently hum, squeal... what it's not relevant is if the RIM is true or not and this is an enorous advantage over vees. BTW... spoke tension also affects vees, so no advantage to vees there.

Had you bedded in the pads properly??? When a pad is not properly bedded in, the brake can do funny things. For example, I had a set of improperly installed brake pads on my rear Julie (bought bike used) and pads are wedged. Wedging can happen with improperly bedded in pads. As the rotor/pads/pistons are being actuated in a way not designed for, it may lead to funny things would happen.

Just my guess.
 

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Potential Roadkill said:
The question I've got is how does the spoke tension/truing effect the brakes? I thought that was one of the advantages of discs to begin with...
Potential Roadkill - Good question. The tolerances of disc brakes are very tight, and it's not unusual to only have a mm or two clearance between the rotor and the pads, and in some cases the rotor and the fork. Forks can easily flex as you ride, and eat up that one or two mm clearance. The rotor is attached to the wheel hub, so if the wheel isn't true, or the spokes aren't evenly tensioned, you can probably picture how a slight wobble could also eat into your tolerances. Disc brakes are the greatest thing since sliced cheese, but they can be finicky. Good luck. - Dave
 

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I had this problem as well.
You might try the alignment again, I had a hell of a time in set-up using the brake squeeze method and then tightening everything.I gave in and went to my LBS and the trick when tightening is to make sure that you stay perpendicular to the nut with the wrench and do it gently, gradually tightenning as you go, two people make this easier.
Every time I tightened the nut I would accidently move the brake off alignment again.
I now have the hang of this but a good mechanic is weight in gold.
 
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