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Old 10-13-2015, 04:19 PM   #1
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Brake rotor question

Curious as to what the common practice is of worn rotors. While mine aren't too bad, I was wondering if our rotors should be replaced when worn, or resurfaced? I haven't noticed much discussion here of resurfacing. With my ordinary cars I'd certainly resurface them if possible.
As always thanks....
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Old 10-13-2015, 04:53 PM   #2
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Because they are drilled they cannot be turned.

It only takes a few MM before they are shot.
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Old 10-13-2015, 05:01 PM   #3
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Base rotors have a spec where they can be turned, S rotors can't. There is 2 mm of allowed wear per rotor before Porsche says they should be replaced. You can get an idea because there is a lip at the top of the rotor, once it gets to 1mm per side they are done.
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Old 10-13-2015, 05:04 PM   #4
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Thanks guys, my rotors are "S" so they are probably close to being shot! Your answers are much appreciated.
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Old 10-13-2015, 07:54 PM   #5
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Here you go

70 bucks a side

Carquest Wearever Brake Rotor - Front YH145464: Advance Auto Parts

I was told Bosch made these, I have been running a set for 2+years
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Old 10-14-2015, 06:24 AM   #6
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steve0x,
I don't understand the "lip" Please explain. New to the 986...still learning.
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Old 10-14-2015, 06:57 AM   #7
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Lip

Flouese, if you look at your rotors, you will likely see a very thin rusty edge at the very outside face of the rotor. The disk brake pads don't come in contact all the way to the very outside edge of the rotor, their contact ends where the shiny part of the rotor ends. The shiny part of the rotor is worn down and made thinner by the brake pads over time. The outer edge is the original thickness of the rotor and rusts due to not being contacted by the brake pad. So if that lip edge is very pronounced, it means the rotor has been worn too thin and needs to be replaced when a brake job is done.
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Old 10-14-2015, 07:12 AM   #8
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Quote:
Originally Posted by PaulE View Post
Flouese, if you look at your rotors, you will likely see a very thin rusty edge at the very outside face of the rotor. The disk brake pads don't come in contact all the way to the very outside edge of the rotor, their contact ends where the shiny part of the rotor ends. The shiny part of the rotor is worn down and made thinner by the brake pads over time. The outer edge is the original thickness of the rotor and rusts due to not being contacted by the brake pad. So if that lip edge is very pronounced, it means the rotor has been worn too thin and needs to be replaced when a brake job is done.
Exactly!

Here is a picture of a rotor lip:

Got a break wear light

From that post:



The only way to know for sure is to measure, but by feeling the lip or lack of it, if the lip is > 1mm it is time to replace the rotor.
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Old 10-14-2015, 07:26 AM   #9
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You can get an inexpensive digital caliper at Harbor Freight. When on sale (just about all the time) around $12.

I measured my with some big washers that were thicker than the lip on both sides of the rotor and then subtracted the thickness of the washers.

Kind of hard to tell what 1 mm is with my fingers
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Old 10-14-2015, 09:36 AM   #10
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If only KRAM were around to answer this........
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Old 10-14-2015, 09:50 AM   #11
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Quote:
Originally Posted by JayG View Post
You can get an inexpensive digital caliper at Harbor Freight. When on sale (just about all the time) around $12.

I measured my with some big washers that were thicker than the lip on both sides of the rotor and then subtracted the thickness of the washers.

Kind of hard to tell what 1 mm is with my fingers
I have that same tool, they just opened up a harbor freight here in my town, yeah.. used to have to drive 45 minutes . About the only thing you can tell with your fingers is "No lip so still mostly new" or "some lip, better measure" or "holy #$% that thing is huge"
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Old 10-14-2015, 10:11 AM   #12
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O'Reilly sells the Bosch zinc coated rotors for $80 ea. No brainer to replace them.
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Old 10-14-2015, 10:41 AM   #13
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Quote:
Originally Posted by steved0x View Post
Base rotors have a spec where they can be turned, S rotors can't. There is 2 mm of allowed wear per rotor before Porsche says they should be replaced. You can get an idea because there is a lip at the top of the rotor, once it gets to 1mm per side they are done.
My "S" rotors have wear spec on them. Of course you can turn them, it will reduce the chamfer depth.
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