new pads/discs need 'bedding in'?
03-27-2007, 05:51 AM
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new pads/discs need 'bedding in'?
Hi All,
just had new front brake pads and discs installed. I've found a link whilst browsing t'internet which suggests bedding in new pads (by 10 repeats of 60-to-10mph braking) is useful to optimise braking and lengthen disc and pad life. Specifically:
"Bedding in advantages:
1. Gradually heat treats the rotor and eliminates any thermal shock in the rotor.
2. Burn off volatiles and moisture from the resin that is near pad surface. This will eliminate “green fade.”
3. Establish a layer of transfer film about a few microns thick on the rotor surface. Shearing of the film during friction is an effective source of friction force. Otherwise, when using a freshly ground rotor without the transfer film, the main friction force would come from cutting, plowing, or scoring the asperities on the rotor surface. This leads to inconsistent braking effectiveness.
4. Mate the two surfaces to a near perfect geometrical match, so that the contact area is high, and therefore the friction force is increased.
5. The performance of a fresh rotor/fresh pad system would be inconsistent. This is due to ever-changing structures and properties of the two mating materials. Bed-in of pads and rotor will form a stable transfer film.
6. If bedding in procedure is not applied, a stable transfer film may not be established for a long time. In other words, the rotor surface would have to be constantly regenerating a film that is not quite stable for a long time. This effect would reduce the performance and increase the wear."
My mechanic didn't mention this to me and I've never done it on any other car - any opinions out there as to whether it's necessary/useful? Is it a racing thing, or relevant to just road use also?
Cheers, Andrew.
just had new front brake pads and discs installed. I've found a link whilst browsing t'internet which suggests bedding in new pads (by 10 repeats of 60-to-10mph braking) is useful to optimise braking and lengthen disc and pad life. Specifically:
"Bedding in advantages:
1. Gradually heat treats the rotor and eliminates any thermal shock in the rotor.
2. Burn off volatiles and moisture from the resin that is near pad surface. This will eliminate “green fade.”
3. Establish a layer of transfer film about a few microns thick on the rotor surface. Shearing of the film during friction is an effective source of friction force. Otherwise, when using a freshly ground rotor without the transfer film, the main friction force would come from cutting, plowing, or scoring the asperities on the rotor surface. This leads to inconsistent braking effectiveness.
4. Mate the two surfaces to a near perfect geometrical match, so that the contact area is high, and therefore the friction force is increased.
5. The performance of a fresh rotor/fresh pad system would be inconsistent. This is due to ever-changing structures and properties of the two mating materials. Bed-in of pads and rotor will form a stable transfer film.
6. If bedding in procedure is not applied, a stable transfer film may not be established for a long time. In other words, the rotor surface would have to be constantly regenerating a film that is not quite stable for a long time. This effect would reduce the performance and increase the wear."
My mechanic didn't mention this to me and I've never done it on any other car - any opinions out there as to whether it's necessary/useful? Is it a racing thing, or relevant to just road use also?
Cheers, Andrew.
03-27-2007, 06:51 AM
#2
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I have read the theory about bedding in brakes. I don't know where it comes from, but ten hard stops in rapid succession will get the rotors up to red hot. The owners manual and the factory service manuals are the authoritative references for these cars. Neither say anything about harsh break-in procedures for new pads.
I have always been very gentle for the first couple hundred miles on new pads on the theory that the high-spots on the pads will overheat and need to wear down during mild stop until even contact is established. My brakes work great and last a long time. Track cars get the brakes much hotter. Pads are changed quite often, and you expect more problems with heat-related damage to the rotors. If you plan to race, there may be benefit to burning in the pads while you still have room to stop. For a street car, I can't see much benefit, to taking the brakes that much hotter than you will see in service.
I have always been very gentle for the first couple hundred miles on new pads on the theory that the high-spots on the pads will overheat and need to wear down during mild stop until even contact is established. My brakes work great and last a long time. Track cars get the brakes much hotter. Pads are changed quite often, and you expect more problems with heat-related damage to the rotors. If you plan to race, there may be benefit to burning in the pads while you still have room to stop. For a street car, I can't see much benefit, to taking the brakes that much hotter than you will see in service.
03-27-2007, 08:14 AM
#3
Rennlist Member
Bedding in pads is the way to do it and most probably your mechanic has already done this for you. I always follow this procedure although I do not run down from 60 mph as it is hard to find a spot to accomplish this in the city and other reading I have done says that 35 to 45 mph is fine. Even on my race car I go out in an early practice session to perform this and for scrubbing in new tires.
