Brakes smoke after replacement: Normal or a problem?

Understanding Why Brakes Smoke After Replacement

Replacing brake pads is a routine maintenance task that ensures your vehicle’s braking system functions properly. However, it’s common to experience smoke and an unpleasant odor from the brakes shortly after new pads are installed. These symptoms can be alarming, but they often have reasonable explanations. This article explores why brakes smoke after replacement. Learn why this is normal and what’s actually happening to cause the smoke and smell.

The Brake Pad Bedding-In Process Generates Heat, Smoke, and Smell

One of the most common reasons for smoke and odor after replacing brake pads is the bedding-in process. When new brake pads are installed, they need to be properly bedded-in with the rotors to ensure optimal performance and longevity. Bedding-in involves gradually heating up the brake pads and rotors to create an even tranfer layer of pad material on the rotor surface.

During this process, it’s normal to experience a burning smell and sometimes even light smoke. This is due to the resins and binding agents in the brake pads reaching high temperatures and burning off as expected. As long as the smoke is light and dissipates quickly over the following two days, it’s not a cause for concern. However, it’s crucial to follow the specific bedding-in procedure recommended by the brake pad manufacturer to avoid glazing the pads or damaging the rotors. There’s no one-size-fits-all bedding procedure. Racing pads, for example, require a hard stop at a high speed, while street brake pads require a far more gentle stop at around 30-MPH.

Grease or Oil Burn-off From the Pads and Rotors

Another common cause of smoke and smell after a brake pad replacement is the burn-off of residual oil from the manufacturing process. The official best practices for cleaning the rotor before installation include removing all the rust-preventative coatings and scrubbing with hot water and dish soap. If you skip this step, some of that manufacturing oil will be left on the rotor and heat up and smoke when you apply the brakes.

Some High-Performance Brake Pads Are More Inclined to Smoke

High-performance or racing brake pads are designed to operate at higher temperatures than standard brake pads. They often contain more metallic components, which can cause increased smoke and smell during the initial bedding-in process or under heavy braking conditions. These pads may also produce more brake dust, which can contribute to the odor.

What is the smell?

Not true. The smell and smoke aren’t caused by oxidation. What you smell is gasses formed during the curing process. It’s a completely normal process, not something you should worry about. The smoke and smell should get significantly better by the second day of driving after pad replacement.

Why do some brake pads need a curing process?

If new brake pads are heated too quickly or beyond a certain heat level, the friction material can lose some strength, and the off-gassing can cause brake fade. So, stomping on your brakes right after a brake job should be avoided unless specifically recommended by the brake pad manufacturer. Some brake pad manufacturers do recommend braking from high speeds, but those pads are usually designed for racing. Street brake friction materials should never be broken in or cured using this process.

What happens during the burnishing or bedding-in process?

Most brake pad manufacturers specify a break-in procedure known in the industry as “bedding or burnishing,” although a few manufacturers don’t recommend any special procedure. The bedding process does several things:

• it cures the friction material,
• it embeds friction material into the pores of the brake rotor to form a transfer layer film coating of friction material,
• it smooths the rotor surface.

Since brake pads differ in their formulation and manufacturing methods, manufacturers may recommend different break-in procedures for each type of brake pad. For example, a manufacturer may use a molding technique that uses less binding resin but bakes them at a higher heat that cures them more fully in the mold. A different manufacturer’s brake pad formula may use a higher-priced or special resin that creates a distinct smell during the curing process.

Common brake pad burnishing procedures

• 10 to 20 gradual stops from 30 mph
• 10 to 20 gradual stops from 30 mph with 30-second rest time between cycles
• moderate driving with no heavy braking for the first 500 miles

Most brake pad compounds will take up to 300-400 miles to fully develop an even transfer film on the rotors.”

AKEBONO burnishing procedure

400 to 500 miles of moderate driving is recommended. Avoid heavy braking.

ATE burnishing procedure

400 to 500 miles of moderate driving is recommended. Avoid heavy braking

BREMBO GRAN TURISMO burnishing procedure

Apply brakes with moderate pressure slowing from 60 mph to 30 mph. Drive one-half mile to allow the brakes to cool, then repeat the procedure 30 more times.

HAWK burnishing procedure

Apply moderate braking pressure 6 to 10 times from 35 mph. Then make 2 to 3 more hard stops from 40 to 45-MPH without allowing the vehicle to come to a complete stop. Park the vehicle and let the brakes cool completely.

Raybestos burnishing Procedure:

If you’re using the brakes for severe duty like police or taxi service, or before track testing, perform a more rigorous burnishing process:

• 8 moderate brake applications from 40 to 10 mph at approximately ¼-mile intervals.
• 8 somewhat harder brake applications from 60 to 10 mph at approximately ½-mile intervals.
• Drive 1.5 miles
• Allow brakes to cool at least 15 minutes either by parking the vehicle or continuing to drive at moderate speeds with minimal brake applications.

©, 2017 Rick Muscoplat