Date: Thu, 23 Aug 2001 09:55:19 -0700
Reply-To: Coby Smolens <cobys5@HOME.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Coby Smolens <cobys5@HOME.COM>
Subject: Re: Reducing brake fade on '88 Westy?
In-Reply-To: <3B85237D.19993279@mindspring.com>
Content-Type: text/plain; charset="iso-8859-1"
All quite right - I did NOT mean to imply you shouldn't use the best brake
fluid you can find - and it certainly DOES make a difference. I have
documented this by my own experience and that of my customers to some extent
since the time when I was going by the OLD VW & Bentley credo, to whit:
"Only use new DOT 3 or DOT 4 brake fluid according to SAE recommendation J
1703 and conforming to MOTOR VEHICLE SAFETY STANDARD 116." At that point we
were using DOT 3 - a hold-over from the days before Vanagons when most of
our work was with buses and Type 1, 3 and 4's.
In fact it was due to posts on this list that I decided to start paying
closer attention to the conditions around cases of fade that I experienced
or were reported to me. In many cases where fade was experienced at a given
location, changing the fluid to DOT 4 resulted in the cessation of the
"second stage" fade described earlier. In other cases where the grade was
too long and steep (15% - there was a detour on US 1 around Fort Ross, CA
due to a mud slide a couple years ago that routed traffic up - and back
down - such a grade) the change from DOT 3 to 4 didn't seem to make a whole
lot of difference, even in vans with all new brake hydraulics, rotors,
drums, linings, and of course, fluid. My own van was one such, loaded to the
hilt with four grown people and their gear for a month on the road. One was
my mother-in-law, bless her, and traveling light is, for her, a foreign
concept (or let's say it's different from mine). I heard similar stories
from customers about this same spot.
We now use only DOT 4 in our shop nonetheless, and I'm interested in trying
some heavier duty stuff too, in conjunction with hunting up new lining
materials.
BUT - nothing you do with brake fluid is going to have ANY effect on the
"first stage" failure described earlier, wherein the pad surface starts to
melt. That is caused by friction and pressure which is a function of
pad/rotor/shoe/drum materials and the force exerted on them. The fluid is
downstream of this material-event and reacts to it according to its own
characteristics.
ANOTHER NOTE: Please be aware that silicone based brake fluids are NOT to be
used (Bentley: "Do NOT add or mix DOT 5 silicone type brake fluid with brake
fluid in car as severe component corrosion may result. Such corrosion could
lead to brake system failure.") in normal circumstances, where existing
brake parts are not replaced. Does anyone know if DOT 5 silicone can be used
if you are using all new stock brake hydraulics and hoses? Or do the rubber
components have to be a special type (silicone-based, perhaps)? This
shouldn't be an issue, really since, as Todd brings up, there are
glycol-based fluids available that match or out-perform DOT 5, so there
isn't much incentive to make the switch. I think the silicone stuff is
non-hydrophilic which means parts might last longer, but you'd want to
change the fluid every couple years anyway, due to the inevitable
accumulation of micro-particulate due to normal wear of internal parts.
Coby Smolens
Valley Wagonworks
VW Bus and Vanagon Specialists
"Intimately acquainted with VW Vans since 1959"
1535 SF Drake Blvd, San Anselmo, CA 94960
415-457-5628
-----Original Message-----
From: Todd Last [mailto:Rubatoguy@mindspring.com]
Sent: Thursday, August 23, 2001 8:39 AM
To: Coby Smolens
Cc: vanagon@GERRY.VANAGON.COM
Subject: Re: Reducing brake fade on '88 Westy?
Great post - I'd add one thing. Which brake fluid you use *does* make a
difference. The DOT specifications only set a MINIMUM boiling point
standard, so
you can avoid Colby's second situation to some degree by using a
high-quality
fluid.
<<snip>>
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