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Gordo-
I am posting this reply as a D-I-Y part-time mechanic. I work on 5 of mine own cars, and all have over a 100K miles and one has 350K miles so I guess I'm fairly competent. I would say that you have an intriguing problem, but in reality, I think it is fairly simple. First, a couple of basics. Your brake pads are always in contact with the large pie shaped steel plates called rotors. Always! The pressure is light while not braking and wield incredible force while braking. But there is always some pressure which comes from the brake booster through the master cylinder, through the fluid in the brake lines to the pistons in the calipers, to the pads, and onto the rotors. So understanding that, you're first question is likely; “how come I didn't hear this noise with the last set of pads before the pads were replaced”? Good question! Your brakes don't squeal while braking because there is so much pressure on the pad against the rotor. But when there is light pressure? It's caused from something else. There are a couple of possible reasons. Did the shop "re-surface, "turn", or "cut" the rotors before installing a new set of pads? These terms describe the process of putting a rotor on a machine and taking a very sharp cutting device to "cut" material off the rotor, but in the process make the rotor a very even surfaced again. This is the primary reason to "cut or turn" a rotor. You want a nice smooth surface for the pad to wear against free of the wear patterns of the last sets of pads. While some mechanics go by the belief that unless the brakes are "pulsating" as a symptom of warped rotors, they shouldn't "cut or turned" them. But the second benefit of "cutting or turning" a rotor is that there is steel material that is left ON the rotor that wasn't worn off from the last set of brake pads. This is often overlooked, or thought to be secondary with keeping as much metal thickness as possible on the rotor at all costs. Each state dictates what the thickness of a rotor must be, after being “machined, cut, or turned”, before being re-installed on the car again. Also, as a personal preference, I recommend replacing rotors either with manufactures OEM rotor bought through the dealer network or specify an American supplier such as Bendix, who uses only US grade metal. I have found in my experience that Bendix rotors are made of good grade metal and are subject to warping. Yes, more than other rotor made in China, but less than OEM rotors. Ok, back on subject… Now when you put a new set of brake pads on the car, sometimes there are edges that cause a slight rubbing interference with the new pads! That's the first set of issues you might be dealing with.
The second issue you might be experiencing is a pad type that is either A) different in composition than your last set or B), slightly a different size (a mm difference can make lots of noise!) There are several different pad materials, composites, etc that are made for different applications (e.g. normal road, performance, track, and racing applications) There are also many sub types and manufactures of even one type of pad. I'll submit my theory is that your mechanic replaced your original pads with a good set of pads for your normal road application, but of a different manufacture and possibly type. Here is a great link to do some light reading. http://www.tirerack.com/brakes/tech/techpage.jsp?techid=86
I think if you politely ask what brand and type of pad your shop installed, that might give you some direction as to how to fix this annoying issue.
Types of pads for you car might be the following: organic material, semi-metallic, ceramic, and others. Since you’re so far away from a dealer and it seems that's an inconvenient alternative, Tire Rack or a good national parts store such as Advanced Auto, Car Quest, NAPA, etc., sell many brands and types of pads. Go to a knowledgeable counter person ands ask for their assistance. And again, Tire Rack in an excellent source of technical support and quality products at reasonable prices. I advise against selecting the cheapest, or a house brand, but rather step up to brands that will replace the pad if you're not completely satisfied with the results. Expect on replacing you rotors every other or ever third set of pads. Braking is far more important than going; it is a very good place to spend a little extra! BTW, once you find a brand and type of pad that you’re satisfied with, stick with it unless it becomes obsolete. Again, short answer is I think there are two possibilies you should look into. Were the rotors "turned or cut"? What pad brand and type did your mechanic replace the OEM pads with? Gosh, this seems long winded, but I hope it helps you understand the principles of the braking system and the nuances of the issues I have learned. Good luck! Jim
posted by 68.109.122...
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