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Brake pads: What to look for What to do when having servicing done

Originally published on www.consumerreports.org

While the federal government sets performance standards for brake systems in new vehicles, there are no government regulations covering replacement brake pads. Given that a large percentage of consumer complaints to the National Highway Traffic Safety Administration (NHTSA) involves brakes—and the brake system is one of the most critical elements of vehicle safety—it’s important to understand the choices consumers face when taking their vehicles to a brake shop. The cheapest brake job may compromise safety, and the most expensive parts may not make your vehicle any safer than the standard part.

Servicing brakes 25 years ago required few decisions other than choosing a mechanic. Disc and drum brakes used only two types of friction materials—semimetallic and asbestos. The mechanic simply replaced the old pad or shoe with the same type. Aftermarket suppliers rarely offered different performance grades or price points for either type of pad.

Today, however, asbestos has been all but eliminated, because it can’t meet contemporary cars’ higher performance standards as well as concern over health hazards from asbestos dust. Automaker suppliers have developed additional friction compounds, and the aftermarket now offers a dizzying array of replacement brake products under dozens of brand names.

The different friction materials in use today often have design compromises. While one may offer superior heat transfer—and therefore better braking performance—it may also be noisier and more prone to depositing unsightly brake dust on the wheel rims. Another friction compound may have a soft feel, and work quietly, but wear out much more quickly.

Do you need new brake pads?

Usually, the first sign of excessive brake-pad wear is a high-pitched squealing.This sound comes from a soft-metal wear indicator that rubs against the brake rotor to alert the driver that a change is needed. Other symptoms can include the vehicle pulling to one side under braking, the brakes grabbing or vibrating, and the brake pedal feeling softer to depress. A grinding sound means that replacement is overdue and the worn brake pads may be damaging the brake rotors. Always check the owner’s manual for any brake-related recommendations, including pad replacement intervals.

Types of brake pads

There are four general types of brake pads for cars and trucks:

Semimetallic: This formula, containing about 30 to 65 percent metal, typically includes chopped steel wool or wire, iron powder, copper or graphite mixed with inorganic fillers, and friction modifiers that bond all the ingredients together. These pads are more durable and have excellent heat transfer, but also wear down rotors faster, can be noisy, and may not perform optimally at low temperatures.

Nonasbestos organic: Sometimes listed as organic or NAO, this type of pad is made from fibers, such as glass, rubber, carbon, and Kevlar, with filler materials and high-temperature resins. These pads are softer and create less noise, but they wear faster and create more dust.

Low-metallic NAO: These are made from an organic formula mixed with small amounts (10 to 30 percent) of copper or steel to help with heat transfer and provide better braking. With the added metal, there is more brake dust and they may be slightly noisier.

Ceramic: These are composed of ceramic fibers, nonferrous filler materials, bonding agents, and possibly small amounts of metal. Lighter in color and more expensive than other brake pads, ceramic pads are cleaner and quieter, and offer excellent braking characteristics without wearing down the rotors.

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