Rick's Free Auto Repair Advice

Brake pad friction material types — adherent versus abrasive

Brake pad friction material types

There are two types of brake pad friction materials; abrasive and adherent

Abrasive brake pad friction material explained

In simple terms, abrasive brake pads create friction stopping power by grinding away at the rotor. The brake pad acts like sandpaper and the rotor is the wood in this analogy.

It’s this mechanical rubbing of an abrasive material against the metal rotor that converts kinetic energy into heat that stops the vehicle. Abrasive pads wear away the rotor surface much faster than it wears out the brake pads.

The most common “abrasive” brake pads are semi-metallic. Due to their construction, hardness and abrasiveness, they provide the best stopping power of all brake pad types. That’s why they’re used on heavy SUV, light trucks and larger trucks.

Adherent brake pad friction material uses a transfer layer

Adherent brake pads operate differently. During the break-in or ‘bedding” operation,  the technician drives the vehicle and makes multiple smooth brake applications to wipe a thin layer of brake pad friction material into the pores of the rotor face. The thin film of brake pad material that adheres to the rotor face is called the transfer layer.

During all future braking the brake pad presses against the transfer layer, creating friction. In adherent braking, kinetic energy is converted into heat by pressing the brake pad against the transfer layer. The heat breaks the transfer layer bond to the rotor, changes the transfer layer on a molecular basis and replaces the damaged transfer layer with a new layer of material from the brake pad. The process of damaging and replacing the transfer layer happens multiple times during braking.

Because the brake pads are always depositing a new transfer layer onto the rotor, the pads wear faster in this system than the brake rotor.

The most common adherent brake pads are non-asbestos organic (NAO) and ceramic.

©, 2022 Rick Muscoplat

Posted on by Rick Muscoplat

Categories




Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN