From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: brake linings
Date: Thu, 14 Sep 1995 18:01:41 GMT
We went down this path about a year ago, if the thread
continues I'll see if I can find my earlier post which had
more detail on the issue.
In article <JMC.95Sep13190213@Steam.stanford.edu>
jmc@Steam.stanford.edu (John McCarthy) writes:
>Today we were told by the Ford dealer that the brake linings on a 1993
>Taurus with 16,000 miles were worn down to the metal and would have to
>be replaced. The car is driven by a very cautious driver (not me) and
>used for errands and chaufeuring children. I was astonished.
There is a high probability that cautious drivers may ride the brakes
more, different driving styles have profound effects on durability of
"consumables" ( brakes, clutch, tires etc.) on cars, and manufacturers
also sacrifice durability for desired properties.
>Eventually the service manager explained that asbestos could no longer
>be used for brake linings and the replacement material wore much more
>quickly. The new material had better be a lot less harmful than
>asbestos, because there will be a lot more of it (4 times as much)
>deposited on the road.
This is not the full story. I suggest you obtain some of the following
"Ultra-short fibers and brake lining materials"
Automotive Engineering v.94 p.51-57 (1986)
This provides comparative performance of several alternatives,
showing that they can match asbestos, and aramid fiber can even
provide better wear resistance.
"Feasibility Analysis of Asbestos Replacement in Automobile and
Truck Braking Systems"
various authors from Ford,GM, NHTSA etc.
Mechanical Engineering March 1990 p.50-56.
This reports mainly on the problems for aftermarket applications,
where systems were designed for asbestos, and duly notes that
newer non-asbestos systems were ready for 1991.
>The ban on asbestos was established largely on the basis of statistics
>on cancer World War II shipyard workers and big efforts were made to
>get asbestos out of schools. Somewhat after the ban, it was
>established that there were two forms of asbestos, one harmful and the
>other not. However, the ban was not modified.
This is not so, there has been ongoing discussions about how the
various fibers should be classified. Try
"The Regulatory and Minerological Definitions of Asbestos and their
Impact on Amphibole Dust Analysis"
J.W.Kelse and C.S.Thompson
Am.Ind.Hyg.Assn.J. v.50 p.613-622 (1989)
The generally accepted view is that width and length of fiber are important,
for more details try
" The importance of width in asbestos fiber carcingenicity and its
implications for public policy"
A.G.Wylie et al
Am.Ind.Hyg.Assn.J. v.54 p.239-252 (1993)
This discusses the current regulations, the fact that asbestiform
particles longer than 5um with widths <1um are responsible, and
recommends changes to the regulations. They note that similar-sized
mineral fibers from other sources may well also cause problems.
>I suppose an attempt to modify it would come under the heading of
>"gutting the environmental laws".
The heading " ill-informed stupidity" might be more appropriate
You might also like to review
"Exposure to asbestos during Brake Maintenance of Automotive
Vehicles by Different Methods"
T.Kauppinen and K.Korhonen.
It's a Finnish study that demonstrates how procedures can be
changed to reduce exposure, unfortunately most home mechanics
don't have access, and continue to air-blow, grind, and abrade
friction materials using procedures that result in high exposures.
>1. Maybe the ban is correct, and we shall have to replace brake
>linings a lot more often. The reduction in death rate has to be
>regarded as an increase in the standard of living even if the ban
>lowers the effective take home pay.
Also be aware ( as with tires ) that certain properties are now
desired to such an extent that increased wear is considered
a minor penalty well worth the gain. Of course the car companies
can get it wrong. Toyota got Chris Amon ( former F1 driver ) to tune
the suspension on their Corona. He produced a suberb handling car,
but the specific tires were 50% more expensive than similar ones,
and only lasted 25,000kms. Brilliant road-holding, but the vast majority
of owners were highly annoyed at the excessive tire wear and switched
to more durable tires - with the appropriate loss of adhesion and
balance that he had provided.
>2. Experiences like mine induce people to support politicians who
>campaign against "excessive regulation" and demand that regulations be
>"cost effective". Those who favor more regulation rather than less
>had better be prepared to work hard to convince the public.
Frankly, any brake repair person that gets asbestosis ( not nice -
appears many years after exposure, shortens life expectancy
dramatically, and quality of life for the last few years is very poor ),
should be able to sue the owners of vehicles with asbestos-lined
brakes if they could have used less toxic alternatives. Note that
I haven't checked on the toxicity status of some the alternatives,
but given the general perception on hazards of small particulates,
some wear modes now may be intended to minimise their production.
>Question re moderation: Would this post be acceptable under your
>(anyone's) idea of what the moderation policy should be?
Fine by me. The references are above, read them, provide
additional ones/information, and tally ho :-)