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Old 12-03-2008, 04:00 PM   #1
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Replacing pads w/o machining the rotors

...just want to see what people's experiences here are when replacing the brake pads without machining the rotors, with rotors still above minimum thickness?

I am basically replacing the rear pads with OEM at 60k, but every now and then i hear from my friends that machining the rotor at this point is useful. They claim this is because the old pads usually leave a coat of material on the rotor, which may not be compatible with the new pad materials.

Any pointers appreciated~
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Old 12-03-2008, 06:34 PM   #2
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I don't think I'll ever machine a rotor again. If its that bad it will just get replaced. I just put new pads on all 4 corners without changing the rotors. Pads bedded in well and breaking is much more assertive than before. I of course also did a full flush and bleed with good fluid.

Unless there is a large amount of grooving you should be good. Just make sure the rotors are in good shape and smooth with no cracks.
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Old 12-03-2008, 06:54 PM   #3
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Porsche says not to turn rotors on our cars. Just replace them every 2nd or 3rd pad replacement.

The original rotors on my car lasted 100k believe it or not.
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Old 12-03-2008, 07:50 PM   #4
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Some suggest to sandpaper the rotors when switching to a different pad compound.
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Old 12-03-2008, 10:10 PM   #5
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Quote:
Originally Posted by timothy
Some suggest to sandpaper the rotors when switching to a different pad compound.
ABSOLUTELY!!!

If you 'mic' your rotors, and they're within spec (assuming there is no perceivable warparge), you do want to remove any traces of the old compound before adding new pads.

Brakes work 'best' when the pad lays down a layer of material on the rotor so you get material-to-material contact.

Sanding the rotors with 80-40 grit sandpaper removes the old compound, leaving a fresh surface to build-up a layer of the new pad material during the bed-in.
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Old 12-04-2008, 09:28 AM   #6
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thanks guys~

...awesome feedbacks, thanks guys. The idea of sandpaper sounds great, i'll definitely give it a try this weekend~
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Old 12-04-2008, 10:45 AM   #7
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I would not bother scrubbing with sandpaper. If you properly bed the pads with a proper break-in procedure, they'll be fine.

Stoptech has some great articles online about brake theory, for instance, here's their take on proper bed-in procedure:

http://www.stoptech.com/tech_info/wp_bedinstock.shtml
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Last edited by eslai; 12-04-2008 at 10:48 AM.
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Old 12-26-2008, 01:57 PM   #8
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New Pads /Old Rotors

Quote:
Originally Posted by 944boy
I don't think I'll ever machine a rotor again. If its that bad it will just get replaced. I just put new pads on all 4 corners without changing the rotors. Pads bedded in well and breaking is much more assertive than before. I of course also did a full flush and bleed with good fluid.

Unless there is a large amount of grooving you should be good. Just make sure the rotors are in good shape and smooth with no cracks.
This all sounds like good logical advice; and best of all IT WORKS! I'm about to be doing this same operation. My question is; which brand / type of pads did you use? And are brake wear sensors really necessary? as some pads don't have the provision for them. Any help or strong opinions will be appreciated.
Thanks,
Andy
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