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-   -   Burnishing or bedding in new brakes (http://www.diychatroom.com/f46/burnishing-bedding-new-brakes-161061/)

polarzak 10-24-2012 06:27 PM

Burnishing or bedding in new brakes
 
I learned a lot on another thread on rotor warping and the real problem. While having always bedded in new replaced brakes, after reading that thread, a couple of questions come to mind.

1. Do auto manufactures bed in the brakes on new cars. My last new car had almost half a mile on it...hardly enough to bed in brakes.

2. Why does every owners manual of every car I have owned (lots) say:
a: Avoid making hard stops for the first 200 miles.
b: During this time your new brake linings are not yet worn in.
c: Hard stops with new lining can mean premature wear.
e. Follow this break-in guideline every time you get new brakes.

Doesn't the owners manual go against the practice of making several hard stops to bed in new brakes?

Just askin' :)

ukrkoz 10-24-2012 09:05 PM

it's not really simply making several hard stops. what you are accomplishing is raising rotors' temperature to above 300 degrees, at whuch point, pad material plastifies an embeds itself into the very outer metal layer on rotor. you are not reshaping anything. you creating two smooth high friction layers.
same could have been accomplished on a lathe. that's what they do with ceramic bedding, when they spin rotors very fast on a lathe type machine, then press ceramic material into them. rotors virtually turn red hot, and that embeds ceramic material into metal.
but, you may rightfully say - well, manual says this or that. sure does. thing is, manuals are practically written by lawyers. entire sections are nothing but manufacturer protection. they sure don't want you to jockey car and iff something in it, suing them, or fixing it for you.
same time, I was told that car jockeys, folks that move cars at the factories, drive the hell out of them. it not only beds rotors but, also, supposed to set piston rings into cylinders better. wise men still recommend replacing factory oil right away, as it's known to have metal shards in it due to initial engine break in.
oh, and anywhere you look online - everyone has same - and from various sources - break in procedure for new rotors and pads.

47_47 10-25-2012 07:03 AM

This is what Bendix recommends.
http://www.brakeandfrontend.com/issu...ontentid=40440
I was taught to make a moderate stops from 40 mph to about 10 mph. Drive the car for a 1/4 to 1/2 mile, and repeat 3-4 times. I guess the aim is to get the brakes to temp, without overheating.

polarzak 10-25-2012 06:13 PM

Thanks ukrkoz. Makes sense to me. Thanks 47 47. More good reading.

ukrkoz 10-25-2012 09:33 PM

Quote:

Originally Posted by 47_47 (Post 1037585)
This is what Bendix recommends.
http://www.brakeandfrontend.com/issu...ontentid=40440
I was taught to make a moderate stops from 40 mph to about 10 mph. Drive the car for a 1/4 to 1/2 mile, and repeat 3-4 times. I guess the aim is to get the brakes to temp, without overheating.

Exactly. 50 down to 15, or 45 down to 10. rapid accelerations, hard stops, with consecutive acceleration and stop again.
Also, for next few minutes after done, complete stop and halt should be avoided, as rotors are still hot, and that creates local pad material bonds to rotor.
look at your rotors. see those "crack" looking lines on them? that's actually pad material stuck on rotors, after you rushed to the red light, then hit the brakes and held them.
some, also, find a nice long steep hill, speed up at the top, and drag brakes all the way down to the hill foot. has to be a mile or so.


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