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Old 12-13-2003, 04:06 PM
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Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
300E - Brake Noise

I replaced the front brakes pads on my '86 300E maybe 5 or 8K miles ago with (I believe) Pagid semi-metallics. They worked, and still do work fine, but they've lately started making a very disconcerting "graunching" noise during the last 10-15 ft or so of stopping, especially when they're cold. It sounds like a sort of muted metal-on-metal sound, as if the pads were worn down to the backing plates. I pulled the pads a couple of weeks ago to check them, and there's plenty of material left on them. The pad compound appears to have quite a bit of metal in it, though. This noise didn't appear until the last 2K miles or so.

I've also noticed that the rotors seem to have considerably more wear on them than I would have expected. The surface is fairly smooth, without any noticeable galling, but there's a deep wear ridge now.

Is this typical for these pads? I've run semi-metallics before in other cars and haven't had this problem. In the near futue I plan to replace them with Porterfield R4-S pad and new rotors, but in the meantime I'd like to find out what's going on with these.


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Old 12-13-2003, 11:13 PM
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Join Date: Mar 2003
Location: Southern California
Posts: 2,007
The noise is just a vibration, which is probably caused by stick-slip friction at low rotor velocity. Most brake pads actually have a lubricant in the material to prevent this. Unless you race the car you don't need such aggressive pads. I run Repco Deluxe (NOT Metalmasters) on my 190E. They're non metallic except for what looks like some copper filiments to transfer heat. They require more pedal effort than the OE pads, but they don't, dust, squeal, "grauch" or chew up the rotors.

I even ran it with these pads in hot lap sessions at Willow Springs (big track) and Firebird in Phoenix. Even on the track the Repco Deluxe were okay. Lots of pedal travel, but they modulated well. With all the pedal travel and effort, I was almost afraid that I was generating so much line pressure that a flex hose would burst, but everything turned out okay.

For normal street use and occassional canyon carving the Repco Deluxe are great, and my projected life based on measuring pad thickness every 15K miles is 75K miles!!!

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