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Tech Talk with Master Power Brakes

The Basics of Brake Noise: The Quiet Braking Checklist

Posted by toby on Sep 7, 2014 1:17:01 PM

Brake noise is one of those aggravating problems that can take some time to diagnose properly.  It is tempting to reach for some lubricant, but this is just a short term fix that doesn’t address the true causes of the problem.   So what causes brake noise, and how do we fix it?

It is important to remember that all brakes make noise.  Noise doesn’t necessarily mean that there is something wrong with your brakes.  When you press the brake pedal, the brake pad comes into contact with the rotor, and this coupling causes the pad and rotor to oscillate and vibrate.  The fancy engineering term for this condition is “force coupled excitation.” The wheel-based brake system components (e.g., the caliper assembly, rotors, the attachment bracket, etc.) create a system that vibrates at certain frequencies, which we discern as brake noise.  It is also worth noting that each vehicle’s brake system has unique wear patterns—different parts of the brake system wear at different rates.

When the noise associated with friction coupling combines with these different wear patterns for the various components of your brake system, diagnosing and solving brake noise can challenge the skills of even the most well-seasoned repair professionals.  Before you reach for a jar of dampening paste, you need to look at each component of your brake system and inspect for loose parts and signs of wear.  What follows isn’t a comprehensive guide to quieting your brakes, but it is a start.  Follow each of these steps, and if you are still having problems, give us a call and we’ll be glad to help out.

Start by inspecting the brake system looking for loose or missing parts.  If you can wiggle the brake pads, caliper assemblies, or other brake components with your hands, imagine what happens when you press the pedal to stop the car on the road.  During this part of the inspection, you should also look for shims or clips that are loose, damaged, or missing.  Loose parts vibrate, which in turn, leads to noise.

After this step is complete, inspect the brake pads for signs of excessive wear. You may be hearing a wear-indicator, which is designed to make noise when the pad has exceeded its normal service life.  As discussed in a previous post, some brake pad materials are quieter than others but remember, if you drive your car aggressively, there may be a trade-off between those quiet organic pads and performance.

Finally, inspect the rotors and drums for signs of scoring and grooving.  Assuming visible wear is present but not too deep, a technician can refinish the rotors and drums. Excessive wear patterns (e.g., warped rotors) may require replacement of the rotors and drums. If replacement of these components is your only option, remember that manufacturers “tune” brake systems to minimize noise.  Have your tech recommend the best rotor and drum combination to match the other components in your system and avoid excessive noise.

Solving brake noise is typically more involved than breaking out dampening paste.  A lubricant or dampening paste may work in the short term, but in most cases, this quick fix doesn’t address the root causes of your problem.  Remember to think of your brakes as a complete system composed of worn or loose component parts that collectively vibrate to create those sounds you hear in the passenger compartment.  And as always, if you still can't solve your problem, send us an email or call and we will be glad to help.

Topics: classic cars, How To Series, Noisy Brakes, Quiet Brakes

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