Author Topic: Disk brake squeal  (Read 933 times)

Svend

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Re: Disk brake squeal
« Reply #15 on: September 05, 2012, 12:20:31 am »
Epic's description of this procedure is far better than mine.  Do what he says and you'll be fine.   8)  And let us know if you've cured the offending noise.

BTW, another little tip that may come in handy:  if the pistons are sticking, you can often free them up by removing the pads and cleaning around the piston body (sliding part) with a Q-tip soaked in brake fluid.  Make sure you use the same fluid as in the brakes themselves to ensure that the rubber seals won't be damaged.  The fluid not only cleans, but also lubricates the piston and cylinder.  Carefully press the piston back into the cylinder with an appropriate tool that won't damage the piston face.  Finish with a dry Q-tip to get rid of the excess fluid so it won't attract more dirt and contaminate the pads and rotor.


jim-ratliff

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Re: Disk brake squeal
« Reply #16 on: September 05, 2012, 07:01:08 am »
Svend, don't be so self-deprecating  :o .  Using the brake to center the rotor was a revelation, and once you said it I wondered why I wasn't smart enough to think of that. I have adjusted the brakes on my bike when I changed wheels, and had dealt with the caliper wanting to walk around, but I had been visually centering the caliper on the rotor.

That (the Q-tip) sounds like a good annual end of the year procedure. 
Before the piston starts sticking.
« Last Edit: September 06, 2012, 09:58:13 am by jim-ratliff »
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Svend

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Re: Disk brake squeal
« Reply #17 on: September 05, 2012, 07:33:06 am »
I don't think a stuck piston is the problem for Lynn's bike.  I was just putting that little tip out there for you to use if ever the need arises.  I've had to do that a couple of times -- both on bikes owned by my father in law that were ridden infrequently (he owns a lot of bikes).  Definitely a good end-of-season PM procedure.  But, while you've got your head under the hood of Lynn's GT, you might as well do a full brake service, eh?  ;D

« Last Edit: September 05, 2012, 08:30:54 am by Svend »

Svend

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Re: Disk brake squeal
« Reply #18 on: September 05, 2012, 09:03:51 am »
Jim, before you do anything to the brakes on Lynn's bike, do make sure that the wheels are properly aligned in the frame and fork.  If even slightly off, that will be enough to cause a rotor to rub on the pads when no brake is applied.  The fix might be as simple as that.....


jim-ratliff

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Re: Disk brake squeal
« Reply #19 on: September 05, 2012, 06:18:29 pm »
After an extensive road test on her bike (2 blocks) Lynn's brakes appear to be fine after adjusting the caliper per the excellent advice here.
Thank you.
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Svend

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Re: Disk brake squeal
« Reply #20 on: September 05, 2012, 08:21:17 pm »
Good one.  Glad it was an easy fix.  Hope she gets on the bike soon....


jim-ratliff

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Re: Disk brake squeal
« Reply #21 on: September 05, 2012, 08:47:11 pm »
Good one.  Glad it was an easy fix.  Hope she gets on the bike soon....
I'm hoping that she can figure out how to STAY ON the bike once she is able to start riding again.   ;D
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jim-ratliff

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Re: Disk brake squeal
« Reply #22 on: September 07, 2012, 09:25:37 pm »
Well, the disk brake problem has been identified -- not by me but by the shop after Lynn requested that we escalate the issue to a higher authority.  Their analysis -- there were no pads in the caliper (AT ALL). So no spring to push the pistons back into the caliper. How the retaining pin came out is unknown.
A bit embarassed not to have noticed, but i just never imagined that the pads could just fall out and didn't notice -- even though it was very obvious once it was pointed out.   :o
Here's hoping that no more damage to pistons or seals has been done.
« Last Edit: September 07, 2012, 09:29:43 pm by jim-ratliff »
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Svend

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Re: Disk brake squeal
« Reply #23 on: September 08, 2012, 07:50:50 am »
Gosh Jim, that is an odd one. I'm not familiar with Shimano brakes, so don't know how solid the retaning clips are, or how they could allow a pad to just drop out. Did you have the wheel off at some point?

Not sure if you do this, but when you have a wheel off, it's a good idea to shove a little shim in between the pads to prevemt someone from squeezing the brake lever and pushing the pads together. Not intended to keep pads from falling out, but if Shimano's are known for that, then this might prevent that too. 

I'm sure the shop tech checked this, but was there damage to the rotor from the piston scraping on the disk? Worth a quick look...


jim-ratliff

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Re: Disk brake squeal
« Reply #24 on: September 08, 2012, 10:05:27 am »
Will check the rotor.
I know about the problems of hitting the brake lever with no wheel on. But i don't feel that is the root. There is a retaining pin that goes through the caliper body and the brake pad clip, and the pin has a spring retaining clip. I assume something caught the retaining spring and pulled it off, allowing the retaining pin to work it's way out. Oh well, we learn what to beware of from past experiences.
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jim-ratliff

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Re: Disk brake squeal
« Reply #25 on: September 18, 2012, 07:22:39 pm »
Final post. Brakes pads were replaced, no further damage to pistons or seals.

Looking forward to getting my biking buddy back on the bike in a couple of more weeks, but probably very gradually. Sitting on the bike seat was the most painful thing she encountered. She may be my "Bronx Belle of Puckish Wit and Charm" but she's also been a pretty tough chick thru this broken pelvis ordeal.
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Svend

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Re: Disk brake squeal
« Reply #26 on: September 18, 2012, 07:39:23 pm »
Wish Lynn all the best.  She'll be back riding soon.  There are still plenty of biking days left until the snow flies.

Keep those brakes in good shape!


jim-ratliff

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Road bike disk brakes
« Reply #27 on: October 25, 2012, 05:34:20 pm »



a very interesting article about the challenges facing road bike disk brakes. i still think they are coming.

http://velonews.competitor.com/2012/08/bikes-and-tech/technical-faq/technical-faq-throwing-ice-water-on-road-disc-brakes_235280
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epic

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Re: Disk brake squeal
« Reply #28 on: October 25, 2012, 06:10:37 pm »
15 years ago they were saying all of those things about disc brakes for mountain bikes.

One of the funny things is that people keep talking about weight. Weight when we live in a world where racers have to ballast their bikes to meet minimum weights anyway. Wouldn't it make more sense to have heavier more effective brakes than a couple of lead weights bolted under you bottle cage?

jim-ratliff

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Re: Disk brake squeal
« Reply #29 on: October 25, 2012, 06:33:29 pm »
Agreed. I would gladly carry the extra weight and wind resistance to have hydraulic disk brakes.
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