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.
Properly bedding in a new set of brake pads involves several hard brake applications followed by a cool-off period.
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.
Imprint of brake pad on rotor
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.
'Bedding-In Your Brakes' have 3 comments
June 27, 2012 @ 5:41 pm Mick
Are you making this up? as a GM mechanic with brake jobs as a fact of life GM never thought to ever mention anything as convoluted as this procedure, just drive normally and avoid heavy use for the first few days, come to think of it, Porsche says pretty much the same thing? My cars, Jag, MG, Triumph, 911. have never exhibited any of the horrific symptoms you decibel, not following your procedures. Even doing brakes on heavy equipment does not require any extreme bedding in procedures, just drive normally and avoid heavy use, initially.
October 12, 2012 @ 1:41 pm Dean Parks
After step 1, you state “without coming to a stop”
After step 2 you state “without coming to a stop”
Step 3 does not mention stopping, but then step 4 says to cool brakes for 15 min. with step 5 implying that the car is stopped.
When(and how) am I supposed to come to a complete stop?
I have to agree with the above comments by the GM mechanic. I have tried bedding in brakes with instructions simular to these and I find I have much better results doing as the GM mechanic above states.
Also, I have never had “bedding in” instructions come with a set of pads, high performance ones or otherwise.
April 2, 2013 @ 1:15 pm Jo Jesty
I’m not so sure… This comment is about the writer’s #2, pulsation. My Healey doesn’t get this problem, probably because I don’t drive it hard and the discs are solid and heavy. But my Acura’s (vented, thinner) front discs sometimes start pulsating for no apparent reason, and it may indeed be from coming to a stop after hard breaking with the pads gripping a really hot stationary disc. Acura says don’t grind these discs: replace them…hmm. I’ve found that this method mostly cures the problem, though perhaps don’t get so fussy. At speed, look way back in the mirror (!) then brake hard, but not to a stop. Lift the pressure off slowly and continue for another mile or so to let things cool. Then do it again. And once more. You may find it cures the problem, at least until you again get a red light when you’re going much too fast!
Jo