Dear concerned car owner:
This unfortunately happens more frequently than we realize. A certain amount of high-pitched brake noise is considered “normal” these days because of the harder semi-metallic disc brake pads that are used on cars now. In my experience, the smaller cars like Honda and Toyota seem to have the most trouble with this. Squeals tend to be heard during the first few stops in the morning when the brakes are cold and somewhat damp from dew, and squeals that are heard during the last few feet while coming to a stop are usually nothing to worry about.
Semi-metallic brakes are made of bits of metal shavings in place of the asbestos material that has been banned by the U.S. government. These semi-metallic brakes have great stopping power and have a long wear life but can cause a high-pitched squeal that drives car owners crazy and frustrates mechanics who can’t get it to go away to please their customers.
When
are squeals not a problem?
Some brands of semi-metallic pads are inherently noisier than
others because of the ingredients used in the manufacture of
the friction material. Think of it this way--the longer life
pads or pads that claim to have more stopping power usually
contain more metallic material; therefore they tend to be
noisy. Yes, they will last longer and could enhance braking
but the chance of causing a squeal noise is very high. The
squealing noise that might be caused from use of these pads
does not affect braking performance and does not indicate a
brake problem.
Brake squeal is caused by vibration between the brake pads, rotors, and brake calipers. Having the brake rotors refinished or trued (machining a small layer of the metal away from the disc brake rotor to make it smooth and “true” again) and a thin layer of a silicone compound placed on the back of the brake pads are a great way to reduce the squeal if the semi-metallic pads are the culprit of the noise and not due to a worn out disc brake pad.
Why does this squeal happen anyway?
The brake rotor is the round metal object that the brake pads squeeze together like the white part of an Oreo cookie. The rotor is metal and has a smooth slick finish, and the brake pads are made of metal shavings and also have a smooth somewhat slick finish. The more metallic material found in the pad the greater the chance for noise, and vise-versa.
The other type of brake pad is called organic. There is no metallic material used in this kind of brake pad. Organic style brake pads can only be used on vehicles that are specifically designed to use them. Improper use of organic pads on a vehicle designed to use semi-metallic can severely reduce stopping ability. Organic pads are softer than semi metallic and usually do not have a squeal problem. Unfortunately due to shorter life expectancy, inability to stop larger vehicles, and the addition of substances like asbestos in their construction, they are not very widely used.
When
are squeals signaling a problem?
Sometimes brake squeals are an indication that maintenance is
required. Some common conditions that cause brake noise are:
Heat cracked or worn “un-true” rotors
Rough finish on resurfaced rotors
Loose fitting brake pads in the brake calipers
Lack of silicone compound on back of brake pad
Missing springs or anti-rattle clips that should be on the caliper or pad
Improper tightening sequence of lug nuts or caliper hardware
Contamination on the brake pad such as brake fluid
Most GM cars are equipped with a small thin piece of metal attached to the brake pad to act as a warning indicator when the pad material is getting low and the brake pads should be replaced. This inexpensive warning device can be deceiving though, because this warning noise is present when the brakes are not depressed. When the brakes are applied, the warning noise goes away because the indicator has now been forced against the brake rotor and is not able to vibrate which causes this whistling noise.
If you hear brake noises other than a squeal, it could mean your brake pads are worn out and need to be replaced. If your brake pedal feels different than normal or if you’ve noticed any change in the way your vehicle brakes (pulls to one side when braking or requires more pressure on the brake pedal), or loss of brake fluid have the brake system inspected at once.
What should I do?
What can you do as a customer to reduce the chance of
squealing brakes? First of all, noisy brakes should always be
inspected to make sure there isn’t a problem with the braking
system. If the pads have worn down to the point where
metal-to-metal contact is occurring, your vehicle may not be
able to stop safely, and you may damage the brake rotors or
drums to the point where they have to be replaced. Sometimes a
few harder-than-normal stops can “de-glaze” the brake pads and
help reduce the squealing noise for a while.
There are many aftermarket brake pads that claim to be “quiet” or have been “designed.” Personally, I have had the best luck replacing the disc brakes on all vehicles with original equipment pads from the dealership rather than using aftermarket brands. It is usually more expensive to purchase these pads from the dealership but the quality is much better. I am an independent shop owner and my whole business philosophy is to buy as little as possible from dealerships but after trying many squealing aftermarket brake pads I found that it was better to pay the extra money.
