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wtf brake pad cutting into rotor??

 
Old 10-01-2007, 04:10 PM
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Yummybud924
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Default wtf brake pad cutting into rotor??

Replaced all 4 rotors and pads on my 944 about a month ago. Using the organic red box pads from Zims (mintex).

anyways this was the first time changing brakes on any car and it wasn't too hard but....

I noticed a lot of brake squeeking especially when slowing down from low speeds. I used anti-squeek on the back of the pads also.

anyays today I'm working on the car and by accident I noticed that teh driver side front rotor has a grove worn into it. It's a groove going all around the centre of the rotor in a perfect circle. The grove is very clear and I can feel it with my finger. looks like the brake pad has somehow cut a groove all around the rotor.

I can't figure out what would cause this.... but it's making me a bit nervous. The brake pad sensor is not connected to any of the brakes so it could not have come out or something.

I kind of noticed that the car also pulls to one side whe braking hard at 100+ km/h on the freeway.

I drive down the mountain coming home from university and I basicly put the car in neutral and use the brakes to slow down now I'm kind of worried..... I roll down at speeds of 120-140km/h in neutral and use the brakes to slow down.

have an appointment for timing belt retension on october 12 so I'll get the porsche shop to take a look at the driver side front brake to see what is causing this.

anyone her have any ideas..... is the rotor ruined now?
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Old 10-01-2007, 04:23 PM
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xsboost90
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time to pull the pads out and check it out.
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Old 10-01-2007, 04:57 PM
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genikz
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Maybe something got between the pad and rotor during installation. That would explain the groove and the squeal.

This used to fix that sort of problem on my old beetle:
put the car in the air
pull the wheel off the corner you're working on
put a bucket under the rotor
spin the rotor while shooting massive amounts of brake clean onto the rotor surface
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Old 10-01-2007, 05:42 PM
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The rotor isn't ruined if it's still well within specs. You can always turn it.


Your other alternative is to live with it and the groove will eventually disappear as the pad and rotor wear once you clean *whateverisinthere* out.

HTH
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Old 10-01-2007, 08:34 PM
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Originally Posted by 944kid View Post
The rotor isn't ruined if it's still well within specs. You can always turn it.


Your other alternative is to live with it and the groove will eventually disappear as the pad and rotor wear once you clean *whateverisinthere* out.

HTH
There is really not enough material on these rotors to turn them and remain within min thickness spec.

The groove may not disappear. When the pad material wears into the groove, the groove will begin to wear at the same rate as the other surface.
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Old 10-01-2007, 08:34 PM
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Have you bedded in the pads yet (multiple hard braking sessions)? It might take a while for them to get fully bedded in. When I replaced the front rotors, it took forever, lots of hard hi-speed braking sessions. I hear some people will only replace 2 rotors (front or rear) at a time because of this.

Which way does the car pull? Check the opposite-side rotor and pad for any 'glaze', and compare it with the other rotor/pad.
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Old 10-01-2007, 09:12 PM
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Originally Posted by chris luckett View Post
There is really not enough material on these rotors to turn them and remain within min thickness spec.

The groove may not disappear. When the pad material wears into the groove, the groove will begin to wear at the same rate as the other surface.
First:
Originally Posted by Yummybud924
Replaced all 4 rotors and pads on my 944 about a month ago.
How would there not be enough material?


Second:
Originally Posted by 944kid
Your other alternative is to live with it and the groove will eventually disappear as the pad and rotor wear once you clean *whateverisinthere* out.

As the rotor gets thinner, material wears away and the pad will eventually even out with the surface of the rotor. Bedded or not. I'm seeing it on my own car...

As long as the groove isn't more than a few thousandths deep it should disappear fine. If it's deeper, either live with the groove or replace the rotor. It's as simple as that.
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Old 10-01-2007, 10:22 PM
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well I'm not really worried about the grove as it is right now but I'm worried about what is causing the groove.

I highly doubt anything got between the pad and the rotor but I'll check it when I have the time or get the shop to check it when my timing belt gets retensioned next week.

also a bit worried about the really loud squeeking when I brake. the brakes seem to work fine but they squeek like crazy it's a bit embarassing. Sounds like I'm driving the city bus when I come to a stop. I just turn up the music for now... The brake pads were mintex reds. The old ones were mintex reds also and did not squeek and they didn't even have anti-squeel or anything on them.

I have done a lot of hard braking on the freeway as I drive the car everyday to school.and also work.

at freeway speeds I don't hear any squeeling from the brakes. At low speeds the squeeling is very annoying and loud.
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Old 10-01-2007, 10:36 PM
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Originally Posted by 944kid View Post
How would there not be enough material?
I suppose you can tell me what the new thickness, min machining thickness and min thickeness at wear limit are. Let me know when you find out.
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Old 10-02-2007, 12:33 AM
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I guess I don't understand why you're (apparently?) more worried about the rotor groove and the squealing than the car's pulling to one side while braking. The latter is a serious safety issue. I'd fix the pulling first and worry about the other stuff second. I'm not sure the groove is a serious problem as long as it's not getting bigger (think slotted rotors).
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Old 10-02-2007, 12:49 AM
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Sounds like something is stuck in between the rotor and pad. Pull the pad back off and see if there is anything in there.

My friend once had a rock jam between his pad and rotor on his durango. Made intense squealing and even got to the point of locking the one wheel up (on a dirt road) while he wasn't even using the brakes. No squealing while driving at speed, but definite noise when at lower speeds.
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Old 10-02-2007, 12:52 AM
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Originally Posted by chris luckett View Post
I suppose you can tell me what the new thickness, min machining thickness and min thickeness at wear limit are. Let me know when you find out.
Can't be more than a few thousandths, which I doubt gets used in one month.


Way to be a wiseass to the non-owner trying to contribute for once.
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Old 10-02-2007, 01:01 AM
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Did you slip the pads in right, and get the springs in there right? Did your pads have an anti-sqeal backing (spring)? Ive never used those pads before. If it drags to one side check your brake line on that side as this could be the cause as well. Finally verify that the caliper is actually sliding!! Is the rotor blued at all? Sounds like the brake might not be releasing well.
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Old 10-02-2007, 01:45 AM
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Originally Posted by austin944 View Post
I guess I don't understand why you're (apparently?) more worried about the rotor groove and the squealing than the car's pulling to one side while braking. The latter is a serious safety issue. I'd fix the pulling first and worry about the other stuff second. I'm not sure the groove is a serious problem as long as it's not getting bigger (think slotted rotors).
it only slightly pulls to the left only under hard braking at high speed so it's not a big safety issue. under normal braking it seems fine. could be a caliper causing the pulling to one side. I'm getting the brake fluid flushed and refilled soon.

yeah I don't know if the grove is getting bigger or not, that's what I'm worried about.
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Old 10-02-2007, 01:50 AM
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guess I'll remove the caliper and pads and see if anything looks odd.

don't think anything is stuck between it. I remember I could spin the rotor by hand when I took the wheel off. if something was stuck between the rotor / pad I doubt I could smootly spin the rotor.
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