squeaky brake pads when NOT braking

[bxd20]

I've had this happen to me twice now over the past decade, on two different cars. Thought I'd share and see if anyone has a fix or can at least explain what is happening.

There is a squeaking sound coming from one wheel, from the disc brake when I am not applying the brake. Touching the brake pedal to eliminate the 'slack' immediately quiets it.

I have tried resurfacing rotors - no help.

I tried sanding the pads down a bit - helped for a few days.

I have tried using grease or Disk Brake Quiet on the backside of the pads, no help at all, it's definitely coming from the friction surface.

I took the pads on the driver's side and swapped them with the ones on the passenger side and the noise followed -- thus it's the pads not the rotors.

All hardware is clean, working well, lubed, there is no sign of overheating, binding, etc.

As I started off by saying, I've had this happen twice now, with the same symptoms. And I'm trying to learn what is happening.

Neither time did this start when the pads were new. It started after perhaps 10,000 to 20,000 miles. In both cases the pads still had at least 50% of material left. In both cases I would say I drive "slightly spirited" but not very aggressive.

Something about the pad material I am guessing changes with time? I would not think it would be a small 'defect' within the pad, otherwise it would have sanded and worn away. Rather once the squeak starts, it only gets louder, albeit very gradually.

It almost seems like the pad 'cooks itself' over time and the composition change becomes more prone to squeak.

Why this happens on one wheel and not the adjacent wheel that has been maintained in the same manner, and why this happens on one car I drive and not another one that has been driven in similar manner, is what puzzles me.

I can probably fix this easily with new pads

but it bugs me.

 

[Ken2]

Look at the edges of the steel backing plate where it contacts the caliper. Those spots are probably shiny from the rub, and that might be the source of your squeal--high frequency rubbing on those spots. Try a tiny dab of caliper grease on the spots.

 

[SwampSurvivor]

Did you install the clips that either came out with the old pads or came with the new pads? A lot of times if you don't install them, that might cause some noise.

 

[LeakySeals]

Yep the clips keep the pads from shifting...and the other big thing is the grease. Not on the pads, the parts (clips, shims, etc). The parts account for 90% of the squeal, actually a high pitched vibration that sounds like squeal. The grease serves as insulation against that.

 

[mechtech2]

I try the anti squeal sauce on the back of the pads again.
It's hard to believe it would not help with this situation.

 

[JosephHarmon]

Wheel bearing play may cause the scraper to contact & squeal then when pads applied/clamped straightens the rotor up lifting the scraper off the rotor surface.

 

[dla]

My 2009 Cobalt SS that I used to have did the exact same thing. Within the first 17,000 miles it completely chewed up the rear rotors. No I wasn't abusing the car it was mainly highway miles.

The slides for the rear caliper was designed without any covering over it. It would work great at first, but as the miles went by the grease was removed by wear and weather (rain and snow). With the grease removed the inside pad would hang up and rest against the rotor creating the same sound you described.

Walking around the car and looking at the rotors everything appeared fine. It wasn't until you actually got under the rear of the car and looked side to side that you saw the rotor problem.

The rotors and pads were replaced under warranty which is unusual given they are seen as wear items. .

 

[Bluestream]

Make sure the pads are installed with the correct inner and outer pad. They often look the same, but will squeal if installed the wrong way

 

[bxd20]

1/ I always clean, then grease (synthetic) the pad "ears", the edges of the backing plates where it meets the caliper. I also always clean (if needed) and re-grease the sliders.

2/ Rotor wear is not excessive or unusual, no pulsation or discoloration. Pad wear is not excessive, these pads have 36k on them and still have half their life, they are the rear pads on my GTO. (The last time this happened to me was my Ford Contour SVT and it was a front set of pads that time.)

3/ Inner and outer pad installed in proper position.

4/ After grease on the backing plate didn't help, I did a thick layer of the Disc break quiet red goop that dries rubbery, it made zero difference.

5/ The noise followed the pads when I swapped them from one side of the car to the other, hence I doubt it's the wheel bearing.

Out of ideas.... planning to put some new ceramic pads on soon.... seems like a waste of "good" pads.

 

[LeakySeals]

Don't rule out a spun wheel bearing. should test it.

 

[mechtech2]

"the noise followed the pads". Therefore not a wheel bearing.

Pads are not a real high dollar item, so go get a premium set.
With pads, get the best you can afford.
At this point, there is not much left to play with. this should fix her up.

 

[bxd20]

Hi everyone.

Thought I'd bring conclusion to this thread. I went and bought NAPA Ceramic SafetyStop pads, around $55, and the noise is gone.

So indeed it was the pads.

It's not so much about the money or 30 minutes to change the pads, I try to understand "what" and "why" whenever I can. It just bugs me that pads that are fine for 30k miles develop this behavior and it seems to be all the way through the pad material which is very weird. The only theory I'm left with is that over time and use, the heat cycles cook the pad and its physical makeup actually gets altered all the way through the friction material. Remember I did sand away a few mm of material and the noise remained, so it's not a simple problem of glaze.

Well it's gone for now and the new pads have a lifetime warranty so I won't lose any sleep.

Thanks for everyone's input!

 

[ChrisW]

Replace brake caliper hardware and if the chamfered edges on the pad have worn flat, re-chamfer them. Sometimes the carrier which holds the pad can wear too and I usually see this when brake hardware is reused too long it'll start to wear the carrier; I think of the brake hardware as a consumable as well, but up to a certain point. If the carrier is worn, then that would have to be replaced to ensure proper alignment throughout pad wear life.