[s-cars] More NAC - Rotor mystery

[Peter Schulz]

Mike:

My understanding is that cementite 
http://en.wikipedia.org/wiki/Cementite  has formed
-it is harder than the surrounding iron and that is why the pads are 
not biting through it, causing the uneven wear.

you will see that it likely is separated from the main rotor material 
by a layer of rust, and you may be able to chip it off with a chisel, 
carbide scraper etc  - but this will likely "unbalance the rotor"

Your choices are to either have the rotor turned  or to replace them.

What's the cause of this?
Being "soft" on the use of the brake pedal is a likely culprit.
If the car sits for periods of time this can also contribute.

-Peter




At 10:22 AM 12/4/2007 -0500, you wrote:
>I appreciate your indulgence gents, because this is 180 degrees away from
>turbo/quattro.  The link below points to shots of of the front brakes on my
>'98 Grand Caravan.  I bought it fairly recently (took it in trade actually -
>he got my '84 300TD and I got $4K plus a well kept Caravan).
>
>I have never been able to get ABS to kick in, just not enough brake power.
>Now I know why.  There was only 1 inch of pad contact, and it wasn't close
>to the outside of the rotor.
>http://picasaweb.google.com/ebaytechextras/Rotors
>
>
>These brakes passed NH State Inspection 2 weeks ago.  Obviously they
>observed the pads from the side and determined there was plenty left on
>them.  The basket weave rims makes it tough to see the rotors.
>
>See how much pad material is left?  These brakes were NOT down to the
>rivets.
>
>What can possible cause this consistent groove in the center of each pad?
>
>I have replacement parts ready to go on, but I'm looking for input before I
>proceed.
>
>
>Many thanks
>Mike
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-Peter Schulz
Chelmsford Ma, USA
http://www.naaclub.org/

1995.5 S6 Avant Emerald/Ecru
1995.5 S6 Avant Silver/Platinum
1991 200 20v Q Avant Titan Grey (for sale)
1991 90 20v Q Red
1991 CQ silver  (eS2 recipient)