When new pads and brake discs are fitted, the most important thing you can do to prevent problems is to properly bed the brakes. This critical step is the initial transfer of friction material from the pad to the disc forming a smooth, uniform layer. It establishes a foundation that’s essential for proper brake performance. It minimizes the chance of laying down uneven, random patches of friction material which will be felt as vibration when the brakes are applied.
All high-performance discs and pads should come with installation and break-in instructions. The procedures are similar for all major manufacturers. Since you don’t come to a complete stop during pad or disc break-in, you have to plan where and when you do this procedure for safety purposes. If you come to a complete stop before the break-in process is completed, there is a chance that nonuniform pad material transfer or pad imprinting will take place, resulting in an irritating vibration during braking.
Basic Bed-In Procedure:
1. After installing a new auto front disc brake conversion kit, perform eight to 10 slowdowns applying moderate pressure from about 30 to 40 mph (50 to 60 kph) without coming to a stop.
2. Make an additional two or three slowdowns applying heavy pressure from about 40 to 45 mph (60 to 70 kph) without coming to a stop.
3. DO NOT DRAG THE BRAKES.
4. Allow at least 15 minutes for the brake system to cool down.
5. While the car is at rest during cool-down, DO NOT APPLY THE BRAKES. If you do, material will transfer from the pads to the rotor and probably give you braking vibration.
After Brakes Are Bedded-In:
At this point, your new disc rotors and/or pads are ready for normal use with a thin, uniform coating of friction material on the rotors. But the full process of building up the friction layer can take 190 to 300 miles (300 to 500 kms) depending on your driving style. There are two situations you should try to avoid during that time, as they can ruin that fragile friction coating, requiring another round of bedding-in.
First, if you drive gently over a period of time with little heavy braking, you can actually strip off the necessary thin layer of friction material on the surface of the disc. This makes your brakes vulnerable to problems again.
You can restore it by repeating the bedding-in procedure.
Second, if you have an incident where you are driving at high speed and have to brake hard coming to a complete stop with your foot on the brake pedal, the pads will imprint on the disc surface, transferring what seems like a hunk of friction material. This uneven material will cause vibration.
You can generally get rid of the excess material with abrasive friction by repeating the bedding-in process. If it’s a bad imprint and you can’t get rid of it this way, take your car to a shop with an on-car brake lathe. This process returns the discs to dead flat and then you can re-bed.
So bedding-in may not be a one-time deal, but it will work with patience. If you continue to have trouble, contact Moss Technical Services.