[sasilverbullet]

I'm putting on a new set of PBR's on the front with my stock rotors. I'm NOT turning the rotors.



How best to bed them in?



Normal driving?



Or should I do the bed in procedure that's basically the stop gradually from 60 to 10 8 to 10 times in a row...and then let them cool before stopping...



Which one? <img src="/forum/images/smilies/968/huh.gif" class="smilie" alt="" />

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[flash]

well, two things, on the presumption that they are the metal masters:



1 - start saving for new rotors - you will very likely glaze the pads over time, and start having what feels like warping - the slightest bit of non smooth surface results in deposits which results in uneven braking - this almost always happens with less than smooth rotors



2 - do a gradual break in - in all of these, do not come to a full stop - 5 mph will do - take it up to 20 - brake gradually - repeat - take it up to 30 - brake gradually - repeat - take it up to 40 - brake more firmly - repeat - take it up to 50 - brake fairly firmly but do not slam on the brakes - repeat - take it up to 60 - brake same way repeat - take it up to 80 - brake same way repeat - then - down to 60 - brake gradually - repeat - down to 40 - brake gradually repeat - down to 20 - brake gradually - repeat - stop - let car cool down for at least 15 minutes



for clarification, braking gradually does not mean light pressure for a long time - you do not want to drag the brakes - it means a nice smooth braking that would not spill your coffee - braking firmly means you would have to put your coffee down, but your passenger would not be yelling at you that you just snapped their neck



this is the only way i have been able to get pads to break in without glazing on any type of hard pad - getting the deposit layer even is the goal here - you would need to do less on an organic pad

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[bob blackwell]

Michael, I have always bedded them in using the procedure on the box "accelerate to 40 mph then apply brakes using light to moderate effort to reduce speed to approximately 10 mph. repeat steps one and two at least 10 times allowing 1/4 mile between cycles". This has worked well for me with no glazing or warping problems and has given very long life of pads and rotors. Good luck, Bob Blackwell.

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[Tom in Austin]

On this subject, what are people's experiences combining: (1) new rotors + existing pads, (2) exisitng rotors + new pads?



I've seen some commentary that "you must always use new pads with new rotors and vice versa"



Now obviously, if you had sigificant wear on either one, then sure, you'd go all-new. But what if you just want to try different pads? Can they be effectively bedded to match existing, not-overly worn rotors?

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[flash]

as long as the rotor is flat, and still within minimum spec, you can successfully swap out pads with no issue - if there are grooves in the rotor at all, this doesn't work well - surfacing is very inexpensive - most machine shops will do it for less than $20 each, even on drilled rotors



the only other thing to consider is that used rotors are thinner, therefore less able to handle high heat transfers - this could come into play if you are driving the car hard



as for bedding them on existing grooves, i had this argument a number of years ago



the very common misconception is in thinking that since a grooved rotor actually has more surface area, that it should be able to stop better - what isn't intuitively understood is that brakes work best when an even layer of deposit is on the rotor, and that this is impossible to maintain with a grooved rotor, because as the pads heat up, the increased surface area of the grooves, act like a heat sink, and change the way the pad heats and lays down the bed, which only happens when the pads are up to temp - the uneven pattern makes for cool spots that work against this - every time you heat up the rotor in this scenario, you tear away some of that bed, and lay down some more in differnt spots - this makes for a very uneven bedding - this is why you get the "juddering" sensation that is often misdiagnosed as warping - the rotor isn't actually warped - the deposits are just uneven, making it pulsate as it goes around



brakes are really very complicated science - race car tuners will tell you that second only to tires, races are won and lost most on brakes - yes, you can get a car to stop, and mixing and matching used and new parts can be done - it's really about how much compromise you are willing to accept in feel, stopping distance, and safety

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[bob blackwell]

Tom, yes. If the rotors are not worn too bad (judgement call?) you can use new pads without any problems. New Rotors and new pads will, of course, work better together since all surfaces are flat and the thickness of both pads and rotors are new. Good luck, Bob Blackwell.

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[sasilverbullet]

First, read this:

http://www.stoptech.com/tech_info/wp_war...disk.shtml



Whenever I change pads on a good set of rotors, I use 220 grit garnet paper and sand off the coating that the other set of pads left behind. Then I do the 'bed' in procedure. This assures that I'm getting a fresh coating on the rotors.



Fyi...when i first bought my car the brakes were squealing bad. I sanded them with 220 grit garnet paper and then did the 'bed' in procedure. All the squealing went away.



Food for thought...

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[Bob Kovacs]

I would never put used pads on new rotors. If I'm replacing the rotors, I replace the pads. Can't say if there is a body of science or engineering supporting this but if you're doing the work to replace the rotors, spend the few extra bucks and replace the pads, too.



--Bob

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