Suzuki RG500 GAMMA

From: Moskito1@aol.com
To: rg500@xs4all.nl
Subject: Brake Fluid Info!!! (long article)
Status: OR

Alright...here's the low down on Brake fluids...It's another tech article.
 This one comes out of "Motocross Action" (Oct 1996) and should cover the
basic question/answer session that's been going on the past couple of
days....Mind you, it's biased towards MOTOCROSS bikes...but it all transferes
directly to any system.

It was no easy chore for the braking industry to find a fluid that had the
appropriate properties to handle the stressed conditions of a hydraulic
braking system.  The fluid needed to be light enough so that the inner
workings of the brake hydraulics would respond instantly to modulation, but
still compatible with plastic, metal and rubber components.  Most
importantly, the fluid had to remain consistent in temperatures that ranged
from 500F (much hotter than the transmission) all the way down to freezing -
and still be able to transfer through the brake lines into the caliper
pistons.

It's due to high heat that one cannot simply fill the master cylinder with
30W motor oil.  Regular oil would expand to the point of exceeding the relief
space inside the master cylinder reservoir until the brakes locked up.  In
cold climates, standard oils will also thicken and cut the fluidity of the
movement.

The fluid answer came in the form of polyglycol, a fluid that stayed
consistent from hot to cold and had the ability to lubricate the moving
pistons and seals.

However, brake fluid is much more complicated than all of that.

WHAT IS A HUMECTANT?
Try this experiment at home.  Fill a cup to the brim with DOT 3 brake fluid
and sit it outside on an unpainted surface.  Within a short time, the brake
fluid will overflow.

"So what?" you ask.  What you have just witnessed is a brake failure in the
making .  Why?  Read on.

Brake fluid is not the same as other fluids (like motor oil).  Hydraulic
brake fluid must remain stable under high temperatures, provide lubrication
for moving parts, seal the system and have a light enough viscosity to react
quickly.  Polyglycol fits the brake fluid profile to a tee.

Unfortunately, glycol, an alcohol derivative, has one nasty habit.  It
absorbs water.  In scientific terms it is a humectant; a substance that
promotes the retention of moisture.

This brings us back to our experiment.  Why did our cup of brake fluid
overflow while just sitting there?  The brake fluid absorbed moisture out of
the atmosphere, dispersing it throughout the fluid and increasing its volume.
 Brake fluid's ability to absorb moisture from the atmosphere is the cause of
95% of hydraulic brake failures.

WHAT IS BRAKE FADE?
Using two small brake pucks to stop a 400-rpm, ten-inch disc that is powered
by a 50-horsepower motor generates heat. (This is taken from Motocross
Action...thus the low HP number) How much heat?  Up to 500 degrees F.  This
heat is transferred through the brake pads directly to the brake fluid.  Even
in a perfect state (with no water contamination), brake fluid can become so
hot that it will boil.  When it boils, it vaporizes int a compressible gas.
 Under braking, the vaporized gas will compress before the hydraulic fluid,
and if there is any lever play left, the pucks compress
later - maybe too much later!  Your brakes get mushy, the lever goes slack
and corners start coming at you fast.  Bad news!

Keep in mind that we have yet to consider that the fluid has been
contaminated with water.  If you kept notes in high-school physics, you will
remember that water boils at 212 degrees F, much lower than brake fluid.
 When water gets in your brake fluid, it lowers the boiling point and cases
the brakes to fade even earlier.  This dilemma is known as vapor lock.  A
more proper term would be vapor fade, since the gas produced by the boiling
brake fluid rarely expands to the point of locking a motorcycles brakes on.

HOW DOES WATER GET IN?
Hydraulic brake systems are sealed, so how does water get in?  There is a
good chance that the brake fluid was contaminated with H2O before you put it
in your brakes.  Or the moisture entered when the reservoir cover was off.
 It's even possible for hydroscopic fluids to pull moisture past them master
cylinder diaphragm.  As a matter of fact, cheap brake fluids are so
hygroscopic (water attractive) that manufacturers have started to use Teflon
brake hoses to keep moisture from being drawn through the rubber.

WHAT IS DOT?
DOT is the acronym for the federal Department of Transportation.  The DOT
administers fluid regulations and monitors the quality of brake fluids being
sold.  The DOT criteria is so high that there are only three companies in the
U.S. that produce brake fluid.  No matter whose name is on the can (as long
as ti's American made), you can guess that the brake fluid came from Dupont,
Dow or Union Carbide.  Europe also has only three fluid manufacturers, and
companies like Motul use these blends (which do offer a different profile
than what is available in America).

WHAT IS THE WET BOILING POINT?
Brake fluid manufacturers that are proud of their product will list both the
dry and wet boiling points of the fluid.  The dry boiling point (which is the
higher number) is taken when the fluid is in perfect condition.  The wet
boiling point is taken with the fluid fully hydrated and at equilibrium.  The
higher the wet boiling point, the less susceptible the fluid is to absorbing
water.

WHAT ARE CINITASTOKES?
The viscous performance of the fluid is also tested at hot and cold
temperatures, and is measured in cinitastokes (cst).  A lower cst. count
indicates a thinner viscosity.  The thinner the brake fluid, the more
responsive it is to the hydraulic pressure emanating from the master
cylinder.  This is good because thicker fluids are slower to transfer energy
from the lever to the pucks.

WHAT IS DOT 3?
In almost all cases, DOT 3 is the least expensive and lowest-performing brake
fluid produced.  The exception to this rule is Maxima DOT3 550 with a 568 dry
boiling point (highest of any American-produced motorcycle brake fluid).
Base:  Synthetic polyglycol.
Dry Boiling Point: Minimum required dry boiling point - 401F.
Wet Boiling Point: Minimum required wet boiling point - 284F.
Viscosity: Viscosity @-40F - 1500-cst.
Compatibility: DOT 4 & 5.1
Color: Clear to Amber.
WHAT IS DOT 4?
Most DOT 3 fluids meet DOT 4 regulations and vice versa (save for Motul's
Racing Brake Fluid 600, which has incredibly high dry and wet boiling points
of 585F & 421F).  Motul 600 exceeds DOT 3's 1500cst. rating by 2% (@-40F) to
be labeled as such.
Dry Boiling Point: Minimum required dry boiling point - 446F.
Wet Boiling Point: Minimum required wet boiling point - 311F.
Viscosity: Viscosity @-40F - 1800-cst.
Compatibility: DOT 3 & 5.1
Color: Clear to Amber.

WHAT IS DOT 5?
The high boiling points of DOT 5 made it the hottest fluid going in the late
 80's (now only Harley-Davidson specs it).  However, the fluid's syrupy
nature wreaked havoc on the system if water or air entered.  Since thick
brake fluid won't allow micro bubbles to float to the top of the reservoir,
unwanted air is dispersed throughout the system (making lever action mushy).
 Unlike a polyglycol fluid, silicone-based brake fluids do not absorb water.
 Instead, the heavier water settles toward the bottom of the hydraulics,
where the caliper resides.  That means a liquid with a low boiling point is
residing in the area that generates the most heat.  If not bled, the caliper
can
also corrode.
Base: Silicone.
Dry Boiling Point: Minimum required dry boiling point - 500F.
Wet Boiling Point: Minimum required wet boiling point - 500F.
Viscosity: Viscosity @-40F - 900-cst.
Compatibility: DOT 5 Silicone base
Color: Purple (the purple color is a DOT mandate indicating a silicone base
that cannot be mixed with the yellowish DOT 3, DOT 4, and DOT 5.1, DOT 5 WILL
NOT DAMAGE PAINTED SURFACES) <-----there's an answer to one of the questions
floating around!!!!!

WHAT IS DOT 5.1?
This European-produced fluid came into existence due to the fast-moving,
anti-lock braking systems (ABS) used on today's automobiles.  DOT 5.1 is the
thinnest fluid and offers the least hot-to-cold change in viscosity.  This
fluid has the highest wet boiling point of any of the synthetic polyglycols.
Base:  Sythetic polyglycol.
Dry Boiling Point: Minimum required dry boiling point - 500F.
Wet Boiling Point: Minimum required wet boiling point - 356F.
Viscosity: Viscosity @-40F - 900-cst.
Compatibility: DOT 3 & DOT 4
Color: Amber.

WHAT DO THE FACTORIES USE?
Although Team Honda, Kawasaki, Suzuki, Yamaha and KTM will use the
best-performing fluids produced, you can expect your motorcycle to e floored
with low-cost DOT 3 fluid.  It is best to replace it after break-in with a
racing DOT 3, 4 or 5.1 fluid (preferably with one that carries the highest
dry boiling point you can find).

The MXA wrecking crew has had good luck with Motul 300.  There are several
important tips to follow when dealing with brake fluids:

*Fluids with high dry boiling points but low wet boiling points need to be
changed often
*Correctly changing brake fluid means completely flushing the system.
*Mixing new fluid with the old immediately lowers the boiling point of the
new fluid.
*Although fluids with higher wet ratings can run longer before water
contamination becomes too great, it's never smart to run fluid longer than 6
months.
*Remove fluid spilled on disc rotors and pads with contact cleaner
immediately.
*Although brake fluid is packaged in a hermetically sealed environment, it's
still not a good idea to purchase a dusty container of fluid that looks like
it's been on the shelf for years.
*Seal the container immediately after use to keep moisture at bay.

Well, that covers it!

No more typing Mommy!!!

Richard

Rob Koopman ( Rob.Koopman@inter.NL.net ) ^{RG500 Index}