LRO: RE: Asbestos

From: RON WARD (ronward@synovustrust.com)
Date: Mon Jun 04 2001 - 08:45:16 EDT

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    It worked like a dream on my 1995 RR (Rangie, not Rolls) Classic. I used Berol / Turquoise No. 12 Drawing Leads that I keep a supply of for a drafting pencil that I used in college. The leads are 5 inches long, pointed at one end and roughly 1/8" in size. I drilled four 1/8" holes about 3 inches into the surface of the leading edge of every pad on the truck. No squeaking this morning and I suppose as the pads continue to wear, exposing the graphite, no squeaking will ever happen.

    Thanks

    >>> Marin.Faure@PSS.Boeing.com 06/01/01 08:29PM >>>
    Date: Fri, 1 Jun 2001 08:43:38 +0100
    From: "Steve Mace" <steve@solwise.co.uk>
    Subject: Re: LRO: RE: Asbestos (was tuning by eye)

    On 31 May 2001, at 10:36, Faure, Marin wrote:

    >> Actually, the graphite does not do anything to lubricate the lining. The
    > purpose of the lead "inserts" in the edge of the lining (not the face) is to
    > dampen the high-frequency vibrations that are the actual source of the squeal.
    > It works for both pads and shoes.

    >Presumably under the assumption that a couple of inches of pencil lead is
    going to alter the mass of the pad/shoe enough to actually alter it's vibration
    characteristics?

    I'm not going to dispute your numbers, but the vibration dampening effect is
    what ROLLS ROYCE said about the technique in a description of it that I
    read many years ago. I first read about the lead thing in the early 1970s,
    so the technique has been around at least that long. (The same RR pamphlet I
    read also described a technique for limo drivers to come to a stop without
    causing the vehicle to rock back slightly, thus avoiding "disturbing" the occupants in
    back.) There was an sketch of the lead thing, and the holes were drilled
    in the edge of the lining on the shoe, NOT in the face of the shoe.)
    As I recall, the Rolls Royce pamphlet did not describe the technique as a way of
    overcoming the problems of asbestos-free brake lining, but simply as a way to
    eliminate brake squeal if you had it. Makes sense, as they were still using
    asbestos in brakes in the early '70s.

    Over the years, I've had the technique described to me by a few mechanics, and
    they all said the same thing- drill the holes in the edge of the lining material
    parallel and as close to the backing plate as practical. Then insert the lead
    cores, which effectively break up the vibration patters. The length of the
    cores should be as long as you can get away with. I use pieces about 3 inches
    inches long on our Range Rover, and I put in four of them in each pad. The
    vehicle had a bad squealing problem at low speeds from day one, but I kept putting
    off doing the lead thing until recently. When I reinstalled the pads, the squeal was
    gone, and so far it's not come back.

    As for dampening vibration, if you give a tuning fork a whack, you can almost
    completely stop the sound by touching it with a just a feather. So I'm not sure
    mass is the only factor affecting the interruption of high frequencies, which is
    what brake squeal is.

    But what I know about physics wouldn't fill a thimble, so I can't make any sort of
    scientific argument supporting the technique as described by Rolls Royce and the
    mechanics I've talked to. All I know is that following their process, brake squeal
    goes away. I would assume that if you drilled holes in the face of the pad or shoe,
    you'd accomplish the same thing for the same reason.
    ___________________________
    C. Marin Faure
      (original owner)
      1973 Land Rover Series III-88
      1991 Range Rover Vogue SE
      Seattle



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