brake squeal aaaargh
Discussion
hi guys. short while back i replaced the discs all round with turbo grooved vented discs and green stuff pads.now while my s4 stops on a penny its developed a very annoying squeal and makes it sound like a banger.one of you guys warned me it may do this. just wondered if you have any tips on how to remedy this little prob. cheers
Barry
Barry
You try any anti squeal coating on the brakes?
They have them in the auto store in paste packs that you put on or I have seen them in a spray.
I have clipped and pasted some hints for you.
Eliminating Squeal
In order to dampen brake system vibration, you have several options to consider: Chemical insulating compound on pad backs, shim insulators between pad backs and the caliper, and high-temperature grease on caliper pins.
Application of anti-squeal compound on the backside of the pad backing plate can serve to prevent pad vibration, although some owners consider this "damper in a tube" a temporary measure at best. If this compound is used, it's critical to allow sufficient curing time before the brake system is used. All too often, installers apply this compound, install the pads, and immediately send the vehicle out of the shop. If the compound is not thoroughly dry and cured, it will simply squeeze out from behind the backing plate on the first brake application, rendering it useless. Apply a heavy bead on the backing plate, and allow it to completely dry before pad installation. This forms an elastic cushion that absorbs pad vibration.
Insulating shims (vastly preferable solutions to anti-squeal compound) install on the backside of the pads, between pad and caliper. Shims provide a permanent vibration damper. Shims are available for a variety of models. If their use is recommended, install them! One aspect that's often overlooked and one that can easily contribute to brake noise, involves the caliper pins or sliding surfaces. If these metal-to metal friction surfaces are dry, they can temporarily bind and chatter during operation, resulting in a squealing noise. Clean and lubricate the sides and pins with a high-temperature silicon grease. Naturally, exercise care when applying the grease to prevent contamination of the rotor and pads.
Sanding the Rotors
That's right, sanding. A common source of brake squeal is due to the vibrations that are generated when the pads make contact with a rotor surface that is not smooth. I know what you're thinking--if the rotor has just been resurfaced, it must be smooth. However, most brake lathes machine-finish the rotor surfaces with a cutting bit that leaves a series of peaks and valleys. A nicely machined swirl finish may look great, but this surface finish can contribute to minuscule pad chatter. Once the chatter starts, a continuing resonance is created (a tiny series of vibrations that build to a harmonic pitch). Once the rotor has been resurfaced on the lathe, sand the surface with 120 to 150-grit sandpaper (you can use a flat sanding block or a DA sander). Perform the sanding while the rotor turns on the lathe to assure a uniform sanding, in the effort to avoid isolated pressure spots. Don't try to achieve a "swirl" pattern, or any distinct pattern, for that matter. As the rotor turns on the lathe, with cutting bit disengaged, apply the sandpaper from the outer circumference of the disc towards the center. Continue this until the distinct machined finish that was created by the cutting bit is no longer identifiable (about 60 seconds per disc side).
This sanding action serves to smooth the rotor surface, eliminating the severe differences between the machined peaks and valleys. "Noise" typically is generated by a series of vibrations. That applies to the human voice, records, and brake rotors. In other words, if you want the brakes to hush, you have to eliminate the vibrations that are created during the pad-to-rotor contact.
Cleaning the Rotor
Most of us love to use spray cans of bake cleaning solvent. It cleans quickly and cuts through nasty grime with ease. And while it certainly has its place as part of any brake job, it probably isn't the best way to perfectly clean the rotor surface after machining and sanding, a thin film of microscopic dust and grit may remain in the tiny valleys on the rotor surface. To assure a clean rotor after sanding, try washing the rotor in a mixture of detergent and hot water. This will do a great job of cleaning the rotor surface. A thin film of fine grit can cause a chatter of squealing problem, so cleaning should be taken very seriously. The detergent and hot water will cut through the fine embedded layer of grit that might remain otherwise. In addition to serving as one of the steps toward reducing of eliminating brake noise, detergent washing can also improve the performance of the brake system. In fact, brake manufacturer tests have shown a gain of as much as 8% in braking torque with sanded and detergent-washed rotors.
>> Edited by cnh1990 on Saturday 28th May 22:26
They have them in the auto store in paste packs that you put on or I have seen them in a spray.
I have clipped and pasted some hints for you.
Eliminating Squeal
In order to dampen brake system vibration, you have several options to consider: Chemical insulating compound on pad backs, shim insulators between pad backs and the caliper, and high-temperature grease on caliper pins.
Application of anti-squeal compound on the backside of the pad backing plate can serve to prevent pad vibration, although some owners consider this "damper in a tube" a temporary measure at best. If this compound is used, it's critical to allow sufficient curing time before the brake system is used. All too often, installers apply this compound, install the pads, and immediately send the vehicle out of the shop. If the compound is not thoroughly dry and cured, it will simply squeeze out from behind the backing plate on the first brake application, rendering it useless. Apply a heavy bead on the backing plate, and allow it to completely dry before pad installation. This forms an elastic cushion that absorbs pad vibration.
Insulating shims (vastly preferable solutions to anti-squeal compound) install on the backside of the pads, between pad and caliper. Shims provide a permanent vibration damper. Shims are available for a variety of models. If their use is recommended, install them! One aspect that's often overlooked and one that can easily contribute to brake noise, involves the caliper pins or sliding surfaces. If these metal-to metal friction surfaces are dry, they can temporarily bind and chatter during operation, resulting in a squealing noise. Clean and lubricate the sides and pins with a high-temperature silicon grease. Naturally, exercise care when applying the grease to prevent contamination of the rotor and pads.
Sanding the Rotors
That's right, sanding. A common source of brake squeal is due to the vibrations that are generated when the pads make contact with a rotor surface that is not smooth. I know what you're thinking--if the rotor has just been resurfaced, it must be smooth. However, most brake lathes machine-finish the rotor surfaces with a cutting bit that leaves a series of peaks and valleys. A nicely machined swirl finish may look great, but this surface finish can contribute to minuscule pad chatter. Once the chatter starts, a continuing resonance is created (a tiny series of vibrations that build to a harmonic pitch). Once the rotor has been resurfaced on the lathe, sand the surface with 120 to 150-grit sandpaper (you can use a flat sanding block or a DA sander). Perform the sanding while the rotor turns on the lathe to assure a uniform sanding, in the effort to avoid isolated pressure spots. Don't try to achieve a "swirl" pattern, or any distinct pattern, for that matter. As the rotor turns on the lathe, with cutting bit disengaged, apply the sandpaper from the outer circumference of the disc towards the center. Continue this until the distinct machined finish that was created by the cutting bit is no longer identifiable (about 60 seconds per disc side).
This sanding action serves to smooth the rotor surface, eliminating the severe differences between the machined peaks and valleys. "Noise" typically is generated by a series of vibrations. That applies to the human voice, records, and brake rotors. In other words, if you want the brakes to hush, you have to eliminate the vibrations that are created during the pad-to-rotor contact.
Cleaning the Rotor
Most of us love to use spray cans of bake cleaning solvent. It cleans quickly and cuts through nasty grime with ease. And while it certainly has its place as part of any brake job, it probably isn't the best way to perfectly clean the rotor surface after machining and sanding, a thin film of microscopic dust and grit may remain in the tiny valleys on the rotor surface. To assure a clean rotor after sanding, try washing the rotor in a mixture of detergent and hot water. This will do a great job of cleaning the rotor surface. A thin film of fine grit can cause a chatter of squealing problem, so cleaning should be taken very seriously. The detergent and hot water will cut through the fine embedded layer of grit that might remain otherwise. In addition to serving as one of the steps toward reducing of eliminating brake noise, detergent washing can also improve the performance of the brake system. In fact, brake manufacturer tests have shown a gain of as much as 8% in braking torque with sanded and detergent-washed rotors.
>> Edited by cnh1990 on Saturday 28th May 22:26
cnh1990 said:
Sanding the Rotors
That's right, sanding. A common source of brake squeal is due to the vibrations that are generated when the pads make contact with a rotor surface that is not smooth. I know what you're thinking--if the rotor has just been resurfaced, it must be smooth. However, most brake lathes machine-finish the rotor surfaces with a cutting bit that leaves a series of peaks and valleys. A nicely machined swirl finish may look great, but this surface finish can contribute to minuscule pad chatter.
What Calvin said about the machining of rotors is correct, "turning" on a lathe is not the correct thing to do because it leaves the peaks and valleys. Brake rotors and flywheels should be Blanchard ground, never turned on a lathe. Turning will reduce the surface hardness, grinding will increase the hardness and give a good surface finnish (allow the rotor to stand up to wear and heat better).
If they are ground, then sanding isn't necessary. Sanding should only be done with carborundum, not normal aluminum oxide based sand paper.
Travis
Vulcan Grey 89SE
www.lotuscolorado.com/vulcangrey/
How new are the green stuff pads? The current manufacture ones are supposed to have anti-squeel camphers on them. I had an old set on mine and they squeeled like crazy! I just had new rotors and the new make green stuff pads installed. I don't know if they are better now as I am out of the country. Jeff at JAE told me about the new ones. Just FYI.
John
www.skynetworks.gotdns.com
John
www.skynetworks.gotdns.com
bazer said:
cheers travis for more info. do you agree with calvin about shims and am i going down the correct road with this method.
Barry
If you have a vibration in the brakes, have them Blanchard ground. If you have a squeal, shim them. The anti-squeal lube works most of the time too.
Or you can try different pad compounds, different manufacturers squeal more than others.
Travis
Vulcan Grey 89SE
www.lotuscolorado.com/vulcangrey/
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