Bedding brake pads — Procedure
Brake pad bedding is a critical step after installing new brake pads. Simply put, the brake pad bedding procedure deposits a thin transfer layer of brake pad material onto the face of the rotor. Adherent style brake pads need this film deposit to work properly. The film deposit on the rotor contacts the friction material on the brake pad during brake application. The film-on-pad compression converts rotary motion into heat and that’s what stops your vehicle.
Abrasive-style brake pads stop your car by rubbing an abrasive material against the rotor. If just the brake pad were abrasive, it would quickly wear out the rotor. So an abrasive brake pad also deposits a layer of brake pad material onto the rotor. It sticks to the rotor, but it’s not as sticky as an adherent brake pad. It’s really an abrasive film rubbing against an abrasive brake pad. So it’s the abrasive material that wears, not the rotor itself (although all rotors wear and rotors used with abrasive pads wear faster).
How to perform a brake pad bedding procedure
Bedding procedures heat up the brake pad to the point where they can deposit a layer of material onto the rotor. That requires accelerating to a specified speed and then stopping with the recommended force. Some brake pad manufacturers recommend coming to a complete stop while others simply want you to slow to the recommended speed. There is no universal bedding procedure; it varies by brake pad manufacturer and the style of the brake pad.
In fact, the temperature range for proper adherent brake pad bedding varies widely, from as low as 100°F to as high as 600°F for street pads and 600°F-1400°F for race pads. So the bedding procedure you use must be application specific. One could try to generate a one-size-fits-all procedure, but too little heat during bed-in keeps the material from transferring to the rotor face while overheating the system can generate uneven pad deposits due to the material breaking down and splotching (that’s a technical term) on to the rotor face.
Some require a hard brake application from a high speed without coming to a complete stop, while others require a moderate brake application from a moderate speed (30-MPH) with a complete stop and a cooling-off period between each stop. Also, the number of braking attempts varies by each manufacturer. So consult the instructions that comes with your new brake pads.
What happens if you don’t perform the brake pad bedding procedure?
You’ll wind up with brake noise, pedal pulsation, and less stopping power.
Why does brake pad bedding create smoke and smell?
That’s a “maturing” or curing of the resins used during the manufacturing process. A smell and some smoke are normal and will go away after a short while.
What are the signs of improper brake pad bedding?
If you slam on the brakes and overheat the rotor, you’ll see a bluish tinge and possibly a grey tint where the brake pads are touching the rotor. The grey tint is a sign that the brake pad material has built up above the rest of the film layer.
Machining is still evident
Brake rotors are designed with a non-directional finish from the factory. During the brake pad bedding procedure, you wear away that finish.
How can you screw up a brake pad bedding procedure?
Not cleaning the rotors before installing. New rotors must be washing with hot soap and water. Yes, you read that correctly. If you skip the soap and water, you’ll be leaving metal manufacturing debris on the face of the rotor and that metallic debris will embed itself into the pad.
Remove all surface rust from the rotor face and cooling vanes.
Clean and lubricate the abutment areas and caliper slide pins. Apply high-temperature synthetic brake grease to the abutment and slide pins. Install new anti-rattle clips (never reuse the old ones) and noise reduction shims). Apply a light film of brake grease to the anti-rattle clips and to the back of the shims.
©, 2019 Rick Muscoplat
Posted on by Rick Muscoplat