rotor break in?

Boduke0220 · May 24, 2018

My stock rotors were toast from slowing down at a few half mile events. Picked up some new powerstop rotors, not drilled or slotted or anything fancy. I noticed they came with no break in instructions. a few years ago I had drilled and slotted rotors on my Terminator and I had to heat cycle them. any ideas on what break in might be?

Nagare · May 24, 2018

http://www.stoptech.com/technical-s...s/stoptech-sport-brake-pad-bed-in-suggestions

https://www.powerstop.com/brake-pad-break-in-procedure/

Break in the pads as follows:

5 moderate to aggressive stops from 40 mph down to 10 mph in rapid succession without letting the brakes cool and do not come to a complete stop. If you're forced to stop, either shift into neutral or give room in front so you can allow the vehicle to roll slightly while waiting for the light. The rotors will be very hot and holding down the brake pedal will allow the pad to create an imprint on the rotor. This is where the judder can originate from.

Then do 5 mod*erate stops from 35 mph to 5 mph in rapid succession without letting the brakes cool. You should expect to smell some resin as the brakes get hot.

After this is complete, drive around for as long as possible without excessively heating the brakes and without coming to a complete stop (Try for about 5 minutes at moderate speed). This is the cooling stage. It allows the heated resin in the brake pads to cool and cure.

After the brakes have cooled to standard operating temperature, you may use the brakes normally.

Boduke0220 · May 25, 2018

gotcha, thanks!

sed6 · May 27, 2018

Neither of those links are sufficient IMHO. They both describe how to bed pads, but fall short of creating enough heat to season rotors. Rotors needs to be brought up to higher temperatures in stages to ensure they won't warp later on. Properly seasoning a rotor means bringing them up to a temperature higher than they will ever see on the road or track. If you fail to do it properly the first time you exceed the seasoning temps you'll warp the rotors. Cook them now under controlled conditions or cook them on the track and watch them warp. You cannot 'over' season a rotor so why not do it right the first time. If you cannot smell them cooking and see them smoking you're not doing it right. Here a link that shows the difference between seasoning rotors and bedding pads and describes how to do it. Properly seasoning rotors will take you at least 1 1/2 hours and possibly overnight.

http://mustangpartstech.com/SuspensionandBrakes/BrakePadRotorSeasoning.html

qtrracer · May 27, 2018

Rotors crack, pit, and do other things but don't warp. The uneven pedal feel undulation of the pedal or "jutter" is from poor pad break-in - high spots on the face. The pads must transfer material evenly on the rotor faces. If that doesn't happen, you get the high spots and that undulating pedal feel typically misunderstood as rotor warp. Bed the pad correctly and there will be no jutter. If that starts to happen (and usually does on street cars taken to the track on occasion), clean off the old material, check run-out and re-bed the pads. Good to go.

Marvinmadman · May 27, 2018

I've machined/turned many warped rotors. :shrug:

qtrracer · May 28, 2018

Marvinmadman said:
I've machined/turned many warped rotors. :shrug:

And that machining cleaned off the high spots caused by unequal pad deposits. Common misunderstanding.

Marvinmadman · May 28, 2018

Have you ever spun a rotor on a brake lathe?

sed6 · May 28, 2018

qtrracer said:
And that machining cleaned off the high spots caused by unequal pad deposits. Common misunderstanding.

Please explain then why when rotors are turned at the parts store they have a minimum thickness beyond which they cannot be turned. If your theory was correct rotors would last forever as you'd only be removing surface deposits and not the base rotor material...

hiccup · May 28, 2018

Never heard of rotor break-in. ..maybe going a little easy on new pads their first few miles.

Norm Peterson · May 29, 2018

sed6 said:
Please explain then why when rotors are turned at the parts store they have a minimum thickness beyond which they cannot be turned. If your theory was correct rotors would last forever as you'd only be removing surface deposits and not the base rotor material...

You're assuming way too much here . . . when turning a rotor you're going to set the depth of cut such that a minimal but finite amount of metal is going to be removed. Otherwise you'd have no guarantee that you've removed the thickness variation (which would all but guarantee that you'd be getting a customer come-back).

Plus, rotors can still unevenly accumulate pad deposits even when worn. And then there's the matter of 'hard spots', which won't machine precisely the same as the non-hardened regions of the rotor (which generally results in the judder coming back).

I've used metal lathes before. Not brake lathes specifically, but the concepts are the same (I've watched rotor turning a few times).

Norm

rotor break in?

Boduke0220

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Nagare

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Boduke0220

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sed6

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qtrracer

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Marvinmadman

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qtrracer

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Marvinmadman

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sed6

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hiccup

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Norm Peterson

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