Bedding-In Brakes

Replacing your brakes is just part and parcel with owning a car. But most people don’t realise that the bedding-in procedure is one of the most important aspects to replacing brakes. Not only does it help to mate the entirety of the pads to the rotors, but it goes a little deeper than that. Most rotors these days come with a layer of oil to help combat surface rust (though it’s worth noting that most of the Zimmermann rotors we have available are not oiled, but have their own special Z-Coat anti-corrosion coating). Brake pads also come with their own sealant painted on to help prevent damage during transit. The surfaces on both the pad and rotor must be cleaned off before the brakes can be used in normal driving conditions. As well as cleaning the unwanted material from the brakes, there are also resins in the brake pad compound that must be cooked out. These resins are added during the manufacturing process and can interfere in the braking performance needed in an emergency situation. But possibly the most important reason for correctly bedding-in brakes is to transfer an even layer of pad material onto the face of the rotor. Ensuring there is an even ‘transfer layer’ across the face of the rotor helps to prevent the brakes from developing uneven pad material deposits in the future, which is the main culprit behind unwanted brake shudder (despite being commonly blamed on warping). Without correct bedding-in, brakes are less effective and can become noisy. Although the purpose is to prepare your brakes, it has the added benefit of allowing you to practice your emergency braking, and helps you to better understand the braking capabilities of your vehicle.

The Preparation

Firstly, it’s of utmost importance that you perform this bedding-in procedure in a safe location. You will need a long and straight piece of clean asphalt with no trees, pedestrians, animals, or other traffic. This typically means going out into a country area. It’s recommended to use a wider piece of road, just in case the vehicle pulls to one side during heavy braking. Only perform the procedure during the day and in dry conditions. If you’ve just installed a new set of pads and rotors, changing your brake fluid before performing the procedure is a good idea to help avoid the fluid from boiling (brake fluid should always be changed every two years). Check your tyres are in roadworthy condition before you leave, and that the wheel bolts have been torqued correctly. It’s worth noting that the following procedure is only designed for standard street brakes, and that any brake fade can be dangerous. Do not attempt to perform the procedure unless it is safe, with lots of room to slow the vehicle with diminished braking performance.

The Procedure

Driving to around 90kph, you will brake heavily (just before the point of the ABS engaging), bringing the vehicle down to around 10kph before releasing the brakes and accelerating again. It’s extremely important that you do not bring the vehicle to a complete stop. Repeat this procedure another six to nine times without allowing the brakes to cool, and depending on the braking capabilities of your vehicle. More stops may be required for slower or lighter vehicles, but it’s important to discontinue if your brakes can no longer stop the vehicle. Also, please be aware that even if your brake fluid is brand new, you will still get some brake fade. This is known as ‘green fade’, and is a result of the resins inside of the pads being turned to gas. A strong smell and even some smoke is normal during this procedure. After completing your first set, take the vehicle for a drive at freeway speeds, allowing the system to cool for a while. Then return to your nominated piece of road and repeat another identical set of aggressive slowdowns before taking the car for another run at freeway speeds to help cool everything. A third set can help, but is usually unnecessary.

The Result

The first lot of slowdowns will ensure full-width contact between the disc and the pad, and clean them of their unwanted coatings. It also prepares the disc by distributing an even layer of pad material across the face. This helps to reduce brake noise and significantly reduces the chance of developing hot-spots across the rotor. The second lot of ten is designed to cook the resins inside of the brake pad. In normal day-to-day driving, and before they have had a chance to be brought up-to temperature, the pads are quite abrasive. Over time they can wear-down the transfer layer on the rotor, creating brake noise and diminished performance. If this becomes the case, then another round of bedding-in will be required.