Good article about bedding in new pads.

[89911]

Bedding in new pads, nice article.
I've heard lots of different techniques and this one is brief and well explained:


http://www.zeckhausen.com/bedding_in_brakes.htm

[john70t]

I've also heard of using 120 grit sandpaper to roughen up the surface of the pads and bevel the leading edge, and brakeclean to get rid of the anti-rust coating on the new rotors that contaminates the pores of the new pads.

I kind of disagree with the artical(without knowing more info) about the break in process about "standard"(OEM) rotors/pads.

I thought the proper way was to be easy on the brakes for the first couple hundred miles: so the pad surface would conform to the slightly wavy rotor face and wear off the shipping coating without pushing molten pad material into the pits of the machined rotor face.
Mabye with new pad material it's designed to have it on both friction faces. Only BMW knows and they're not telling much

Also, purposely heat treat (BLUE) the surface of the rotors so it's hard and brittle???

[89911]

Although this may be more perfromance oriented then street, you have to get the pads up to temperature relatively quickly to burn off any compounds the lie between the pad and the rotors. Failure to do so and to use your pads for an extended time can actually lead to glazing which is bad. This again is for pads requiring higher heat to function properly. OEM pads don't require as much heat to function and hence, less break in.

[RoninLB]

Originally posted by john70t

Also, purposely heat treat (BLUE) the surface of the rotors so it's hard and brittle???

that's interesting..
what do you do? put it in an electric oven till 400deg for 20min?

[jmohn]

Over time I've read several descriptions (some from pad manufacturers) detailing the proper "break-in" of new pads. The procedure described in the site listed in the first post is (with some minor variations) the same as other procedures I've found.

FWIW, I break-in new pads very similarly to the procedure described. It's necessary to "cook" new pads to bake away the surface resins (prevents "green fade"); when the pads fade you know you've heated them enough. Best to do it in a controlled way rather than have it happen unexpectedly.

BTW, I don't think a slight blue tinge to the rotors would consitute "heat treating" (nor is that the intention) or cause them to become brittle. A deep blue color, however, would indicate extreme heating (to the point the metal would "glow") and would affect the characteristics of the metal. One would not cause this, however, by following the procedure as described.

Jerry M
'78 SC

[Quicksilver]

The best reference for bedding brake pads is Carroll Smith's "Prepare To Win". His books are by far the most accurate, complete, logical, clearly explained, and easy to read of anything available. If you don't have his books go buy them. When you are done reading them you will not only see the answers, you will know how to come up with the answers.

Never sand the pads. You are just imbedding abrasives into the surface of the pad. Besides, why would you want to remove pad material when you just paid money to get more pad material? The pads are so soft compared to the cast iron that the surface texture of the pad is irrelevant.

The pads need to be bedded to "heat treat" the pad material. The pad material is basically glued together and like any glue the curing process involves off-gassing. When the surface temperature of the pad is first raised up to the higher portions of its operating range the binders will boil out of the pads surface with an effect similar to an air hockey table. You have to get these volatiles boiled out of the pad before any serious brake use otherwise you end up using solid objects to stop the car. The pad will gradually off-gas for the rest of its life but it is at a much-reduced rate. This constant off-gassing is one of the reasons for slotted or drilled discs.

To keep from damaging the pad in this initial heat treatment you must get it slowly and thoroughly up to temperature then let it go firmly into green fade. Following this you should let the heat dissipate somewhat slowly. Don't cool them too fast by driving quickly with cooling ducts. You shouldn't park the car with the brakes hot when bedding them either.

If you are serious about brake performance then you should have the discs blanchard ground to provide a true surface that will properly brake in the pads. The discs shouldn't be cut on a lathe but if that is your only option then it is better than nothing. Grinding the discs will also help stop the generation of heat cracks so it gives an extra bonus.

The best break in procedure for the rotors is not the same as for the pads. They really want to be heated a little slower and kept at temperature longer while cycling through their upper temperature range, and then reground afterwards. I don't personally know anyone that goes to all that trouble though. If I was running a 6+ hour race I would do it but I'm not.


Wayne

[Bill Verburg]

Dave Zechausen knows his stuff. He gave a good description of how to do it that is in line w/ any other competent advice in that area.

[BGCarrera32]

what do you do? put it in an electric oven till 400deg for 20min?

LOL...only after I've powder coated the braking surface for increased longevity...

I'm left wondering how many people actually blanchard grind their discs...

[Early_S_Man]

The article is only slightly different from Carrol Smith's procedure ... first published in Sports Car Graphic 30+ years ago, a couple of years before Prepare to Win was published. I have used Smith's procedure on many different cars ... much to the horror of a few owners I took along for the ride, and much to my amusement! Never had any problems after the bedding, and the 'feel' was always improved over 'green' pads!

john70T ... you can't 'take it easy' for a few hundred miles in a race car ... hence the reason for bedding-in new sets of pads before they will be installed at the track during a race! My contention has always been that you never know when you will need maximum performance from a new set of pads and rotors, so the 'take it easy' hogwash seems a bit risky to me! The last thing in the world you need in an emergency situation ... is 'green fade' from a new set of brake pads!!!

[Quicksilver]

Originally posted by Bill Verburg
Dave Zechausen knows his stuff. He gave a good description of how to do it that is in line w/ any other competent advice in that area.

I agree that Zechausen's instructions will give you bedded pads, but they aren't straight to the point. If you don't know exactly why you are doing something than you are apt to make mistakes.

My biggest problem with his instructions is in section 4 where it says, "...the brakes may begin to fade slightly...". You are trying to boil the volatiles out of the pad surface under controlled circumstances so they won't green fade when you really need them. They should fade amazingly if the burn in is thorough enough. You should be warned to have a long straight section of road so you don't test your off road abilities.

Also in section 8 it says, "After the first break in cycle shown above, the brakes may still not be fully broken in... ". This would only happen if the pads weren't completely heat soaked before the green-fade burn in, or the burn in wasn't aggressive enough.

My last problem with the instructions is there is no way for an inexperienced person to judge if the brakes are done.

I just really like people to understand what they are doing. Zechausen's method will work and it is much better then someone heading out into the world with green pads but I think it misses the mark on clarity.


Wayne

[Eric Coffey]

Good info. Just for another spin, here are the procedures that Pagid recommends for their race & street pads:

Street pad bedding

Race pad bedding