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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