Brake squeal and now steering wheel shimmy

Tiny
MP03RSXR
  • MEMBER
  • 2003 ACURA RSX
  • 2WD
  • MANUAL
  • 83,100 MILES
Acura RSX Type-S 2003. 3 years ago the brakes on my passenger right side were squealing loud. I replaced both front pads and noticed the old pads on that side were cracked (causing the squealing when braking). Within a week of replacing the pads, the squeal came back again and has been persistent for the last 2 years. It only starts to squeal after I've been driving around for a while and the car is "warm." It's a rotational squeal that is only heard when braking. So, recently, I replaced all brake pads and rotors on the car with aftermarket (brand new). Already, the same squeal is starting again (it's more subdued than it was before, but it occurs in the same way- it's a rotational "squeak. Squeak. Squeak" that happens after I've been driving around for a little while). I now also have a strong steering wheel vibration when I hit 35-40 MPH. I won't go on the highway because the shimmy "speeds up" - it's not more violent, just more frequent because I'm moving faster. I had all 4 tires replaced and balanced to no avail- it didn't help at all (I needed new tires anyway). There is no shimmy at low speeds or when braking, only at and after 35-40 MPH is it present. Called a Honda dealership today (no Acura dealership in town) and he's not sure what it could be; he said they'd recheck the balance, but ruled out warped rotors as it doesn't shimmy when braking. I have these two problems; rotational squealing when braking and now steering wheel shimmy at and above 40 MPH. Any ideas before I go have these guys look at it and diagnose it? My best guess is something in the suspension/wheel hub/wheel bearing. Please remember that the squeal has always existed since I bought the car and through 2 changes of brake pads and 1 change of rotors. The shimmy only began after replacing all rotors and pads.
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Monday, June 6th, 2011 AT 6:36 PM

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Tiny
CARADIODOC
  • EXPERT
I can suggest a few things. First, it sounds like the right caliper is sticking and not releasing properly. That will cause the pads to grab harder in one spot on the rotor once per wheel revolution. That may or may not be felt in the pedal and / or the steering wheel depending if there is thickness variation warpage or if the braking surface is simply tilted relative to the center hub. If you HAD to use a c-clamp to retract the piston in that caliper to fit the new pads in, that piston is sticking. They should move freely enough to be pried in with a screwdriver before the caliper is unbolted.

When a caliper sticks, the brake will stay applied and overheat and melt the glue holding the lining material together. That will lead to glazing of the rotor and braking material. Glazing leads to squealing. To verify that is the cause, remove the wheel and use course sandpaper to scuff up both sides of the rotor to remove the shiny surface. That roughness will grind the layer of glazing from the brake pads too, then the squeal will be gone for a little while.

Next, check for rust or scale between the rotor and mounting hub. You can see the effects of that by jacking the front end up, running it in gear, and watching the wheel to see if it's moving back and forth sideways as it rotates. This is more common when reinstalling used rotors and the normal round rust spots aren't scraped off, but scale can break loose and get stuck in there too.

It's also common for new brake rotors to warp, especially those made in China. A simple machining will take care of that. Cast iron parts made here are "aged" for 90 days before their final machining. Parts made in China are perfectly fine but they cast, machine, pack, and ship them right away, then they age on your car and sometimes warp. One machining is all that's needed to solve the shimmy or vibration.
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Monday, June 6th, 2011 AT 7:03 PM
Tiny
MP03RSXR
  • MEMBER
I can actually hear the pad rubbing on the rotor from time to time (it's a soft whisping sound- nothing that I can feel while driving); the only weird thing is that I was able to push the caliper piston in with my hands just fine when replacing the pads, so I'm not sure if that's considered "sticking." I didn't realize it'd glaze and cause the squealing. As for the rust between the hub and rotor, there was some and it was tough to get the old rotor off- I had to kick it a few times to break it loose (thanks to acura forums who suggested that; afterward, I realized I could pry it off using the bolts slots)- my fear is that I knocked the hub or something in the suspension loose by hitting the old rotor when it was on; hopefully a simple adjustment/alignment fixes it. As far as the rotor being warped, I hope not because I bought them from autopartswarehouse online- they're Centric Power Slot rotors (slotted) and shouldn't need any sort of resurfacing/machining.
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Monday, June 6th, 2011 AT 7:56 PM
Tiny
MP03RSXR
  • MEMBER
I went out there and jacked my car up and turned the wheel. I can hear the pads rubbing, but more-so in one particular spot each time. I watched the tire while turning it and could see it rising and falling- my guess is about 1/4 an inch. When it dipped low is when the sound and friction from the brake pad was most. Also to add- when I replaced the rotors, someone had already done some work to them- the 2 holding screws on the rotors were longer than the other stock screws and I couldn't get them out- I had to drill them out. Unfortunately, I messed up and had to redrill and tap new holes into the hub to do this; I'm starting to think my redrill wasn't precise and is causing the up-and-down motion as the wheel spins. I'm assuming I'm going to have to pay for a new hub assembly + install. What do you think?
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Monday, June 6th, 2011 AT 8:22 PM
Tiny
CARADIODOC
  • EXPERT
It's normal to hear the pads making a light noise when you're right by the wheel. Also, since you could press the pistons into the calipers by hand, they are not sticking and very likely glazing is not the issue. Check the caliper mounting bolts to be sure they aren't rusty or bent. The caliper has to be able to slide back and forth sideways freely.

As for the rust I'm referring to, if you look at the hub when the rotor is removed, you will see the wheel studs installed through holes in the hub and there will usually be one or three additional holes between the studs. Water splashes up there, through the holes, and onto the backside of the rotor. That's where the round spots of rust build up. Those have to be scrapped off to insure it will sit perfectly straight on the brake lathe and on the hub. If the rotor is reinstalled in a different orientation with that rust spot still trapped in there, it will prevent the rotor from sitting perfectly parallel to that hub. That will cause the caliper to shake sideways back and forth with each wheel revolution, AND it will make the wheel and tire wobble too.

That said, that isn't the concern here because you installed new rotors so there aren't going to be any rust spots.

The screws you drilled out sound like they are the ones that hold the rotor to the hub. Those are used to hold them on while the car is being flipped around on the assembly line. You don't have to put them back because the wheel will hold the rotor tight.

Getting back to the noise concern, there are many things professionals do to prevent noises and there are some things do-it-yourselfers can do to cause noises. Here's a copy / paste version of a reply I post quite often:

To prevent a crunching sound when cornering, put a light coating of high-temperature brake grease between the hub to rotor contact points. This is especially important on older GM fwd cars. Do not get any grease on the pad or rotor friction surfaces. That includes fingerprint grease. Some very picky shops and mechanics will discard pads that get soiled with any kind of grease, but it is usually sufficient to wash all friction surfaces with brake parts cleaner. If this is done before final assembly, there should be no problem. If that grease is there when the parts get hot from normal braking, the grease will soak into the linings and the porous cast iron rotors. It will cause a squeal and never come out.

Another way to prevent squealing brakes is to remove the sharp edge from the leading surfaces of the linings. I used to use a bench grinder, then switched to a flat file. Now I've found it is sufficient to rub the sharp edges on the concrete floor. That removes the "fingernails on the blackboard" screeching. It seems if you can prevent that squeal during the break-in period, they won't squeal later either.

Run a flat file over the pistons and caliper fingers that contact the outer pads. You don't have to shine those surfaces up. The goal is just to be sure there's no dirt or rust that will prevent flat, even contact between the pads' backing plates and the pistons and calipers. Uneven contact will allow the pads to vibrate more than normal. That can set up an audible squeal. Those same contact points should also be coated with brake grease. That can let the pads vibrate without transferring the noise to the calipers where it will be amplified.

Anyplace the pad backing plates or calipers rest on a metal mounting bracket should also have a light coating of grease. That includes chrome-plated mounting bolts that hold the calipers to the mounts. If those bolts have rust pits or are bent, they should be replaced.
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Monday, June 6th, 2011 AT 9:29 PM
Tiny
MP03RSXR
  • MEMBER
Well, the rubbing noise I can by my wheel is distinct and I can actually feel the friction at the low point in the tire's rotation that I talked about. I went back and had a re-balance and it's still about the same shimmy. That noise on that particular wheel can be heard from inside the car with windows down (and I have a fairly throaty exhaust)- I can hear a "whooshing/wisping" sound while I drive- the pads are definitely contacting the rotors at all times. I can see uneven wear lines after just driving around a few times after bedding the pads- it's as if the middle of the pad isn't contacting at all (I find it very odd)- the inner and outer surface of the rotor is blackened, but the center is pretty much perfectly clean. Since it's easy to remove the calipers and rotor, I'm going to check, reinstall, and grease everything again this evening- I'm going to make sure I can compress the piston all the way (I was able to get the new pads on by compressing the piston with my hands, but it was a very tight fit over the rotor). I have an aerosol brake cleaner, so I'll use that in/around the piston; I've never removed the seal before, but it's worth cleaning, just in case it is sticking.

I just find it odd that this problem has persisted through 3 different pads as well as a rotor change. I feel like something I did while changing the rotor had to cause this steering wheel shimmy- it was not there prior to changing the rotors and pads. I can feel a slight pull when coasting- like I said, I know I can hear the pad touching the rotor when the brake is not engaged. Hopefully disassembly, cleaning, reassembly will help and fix the problems. Thank you for the inputs! I feel like at least now I'm not going to spend hundreds on parts and labor at a dealership/garage!
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Monday, June 6th, 2011 AT 9:56 PM
Tiny
MP03RSXR
  • MEMBER
Just a thought- could the brake pad making contact with the rotor at all times cause the shimmy that I'm feeling? As in both problems (squealing and shimmy) caused by the pad friction?
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Monday, June 6th, 2011 AT 10:40 PM
Tiny
CARADIODOC
  • EXPERT
Yes, it can easily cause a shimmy, but that is due to a sticking piston which it appears you don't have. That type of shimmy gets worse as the brake heats up.

It's normal for the pads to stay in contact with the rotor, but just lightly. That creates the squeegee action that clears off water to prevent brake fade after driving through deep water. When you apply the brake pedal, the seal around the piston sticks to it and deforms, (bends) a little. When you release the brake pedal, that seal straightens out and pulls the piston back just a couple thousandths of an inch. That's what releases the pressure between the pads and the rotor.
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Tuesday, June 7th, 2011 AT 1:42 AM
Tiny
KHLOW2008
  • EXPERT
Remove the rotor and check behind it and the hub for foreign materials lodged in between. If any hard rust had gotten in between the hub flange and rotor, the hub would not seat laterally.
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Tuesday, June 7th, 2011 AT 2:23 PM

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