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Re: [ST] Brake Fluid Explained (Long)



I'm having hassles with the brakes on the Daytona.

They went soft after 4000kms, so I bled them & topped up with 5.1 on the
advice of the dealer. (Back bled first then beld the usual way)

They were perfect for 1000kms, now they are going soft again.

I've written an email to the dealer, who has forwarded it to the technical
guys. I'm apparently not the only customer with the problem, some of the '05
speed triples have the same problem.

I'll let you know what the cure is.

cheers

Marc
Cape Town, RSA


On 4/6/06, John Ulizzi <jaulizzi@xxxxxxxxxxxxx> wrote:
>
> Thanks for sharing , Brett. That clears up a couple
> questions for me....
>
> John
>
> --- brettwilson21@xxxxxxx wrote:
>
> > I grabbed this off www.bikersoracle.com interesting
> > reading if you're wondering whats really going on
> > with brake fluid.
> >
> > Enjoy,
> > Brett.
> >
> > Brake Fluid Facts
> > by Steve Wall
> >
> > As a former materials engineering supervisor at a
> > major automotive brake system supplier, I feel both
> > qualified and obligated to inject some material
> > science facts into the murky debate about DOT 5
> > verses DOT 3-4 brake fluids. The important technical
> > issues governing the use of a particular
> > specification brake fluid are as follows:
> >
> > Fluid compatibility with the brake system rubber,
> > plastic and metal components.
> > Water absorption and corrosion.
> > Fluid boiling point and other physical
> > characteristics.
> > Brake system contamination and sludging.
> > Additionally, some technical comments will be made
> > about the new brake fluid formulations appearing on
> > the scene.
> >
> > First of all, it's important to understand the
> > chemical nature of brake fluid. DOT 3 brake fluids
> > are mixtures of glycols and glycol ethers. DOT 4
> > contains borate esters in addition to what is
> > contained in DOT 3. These brake fluids are somewhat
> > similar to automotive anti-freeze (ethylene glycol)
> > and are not, as Dr. Curve implies, a petroleum
> > fluid. DOT 5 is silicone chemistry.
> >
> > Fluid Compatibility
> >
> > Brake system materials must be compatible with the
> > system fluid. Compatibility is determined by
> > chemistry, and no amount of advertising, wishful
> > thinking or rationalizing can change the science of
> > chemical compatibility. Both DOT 3-4 and DOT 5
> > fluids are compatible with most brake system
> > materials except in the case some silicone rubber
> > external components such as caliper piston boots,
> > which are attacked by silicon fluids and greases.
> >
> > Water absorption and corrosion
> >
> > The big bugaboo with DOT 3-4 fluids always cited by
> > silicone fluid advocates is water absorption. DOT
> > 3-4 glycol based fluids, just like ethylene glycol
> > antifreezes, are readily miscible with water. Long
> > term brake system water content tends to reach a
> > maximum of about 3%, which is readily handled by the
> > corrosion inhibitors in the brake fluid formulation.
> > Since the inhibitors are gradually depleted as they
> > do their job, glycol brake fluid, just like
> > anti-freeze, needs to be changed periodically.
> > Follow BMW's recommendations. DOT 5 fluids, not
> > being water miscible, must rely on the silicone
> > (with some corrosion inhibitors) as a barrier film
> > to control corrosion. Water is not absorbed by
> > silicone as in the case of DOT 3-4 fluids, and will
> > remain as a separate globule sinking to the lowest
> > point in the brake system, since it is more dense.
> >
> > Fluid boiling point
> >
> > DOT 4 glycol based fluid has a higher boiling point
> > (446F) than DOT 3 (401F), and both fluids will
> > exhibit a reduced boiling point as water content
> > increases. DOT 5 in its pure state offers a higher
> > boiling point (500F) however if water got into the
> > system, and a big globule found its way into a
> > caliper, the water would start to boil at 212F
> > causing a vapor lock condition [possible brake
> > failure -ed.]. By contrast, DOT 3 fluid with 3%
> > water content would still exhibit a boiling point of
> > 300F. Silicone fluids also exhibit a 3 times greater
> > propensity to dissolve air and other gasses which
> > can lead to a "spongy pedal" and reduced braking at
> > high altitudes.
> >
> > DOT 3 and DOT 4 fluids are mutually compatible, the
> > major disadvantage of such a mix being a lowered
> > boiling point. In an emergency, it'll do. Silicone
> > fluid will not mix, but will float on top. From a
> > lubricity standpoint, neither fluids are
> > outstanding, though silicones will exhibit a more
> > stable viscosity index in extreme temperatures,
> > which is why the US Army likes silicone fluids.
> > Since few of us ride at temperatures very much below
> > freezing, let alone at 40 below zero, silicone's low
> > temperature advantage won't be apparent. Neither
> > fluids will reduce stopping distances.
> >
> > With the advent of ABS systems, the limitations of
> > existing brake fluids have been recognized and the
> > brake fluid manufacturers have been working on
> > formulations with enhanced properties. However, the
> > chosen direction has not been silicone. The only
> > major user of silicone is the US Army. It has
> > recently asked the SAE about a procedure for
> > converting from silicon back to DOT 3-4. If they
> > ever decide to switch, silicone brake fluid will go
> > the way of leaded gas.
> >
> > Brake system contamination
> >
> > The single most common brake system failure caused
> > by a contaminant is swelling of the rubber
> > components (piston seals etc.) due to the
> > introduction of petroleum based products (motor oil,
> > power steering fluid, mineral oil etc.) A small
> > amount is enough to do major damage. Flushing with
> > mineral spirits is enough to cause a complete system
> > failure in a short time. I suspect this is what has
> > happened when some BMW owners changed to DOT 5 (and
> > then assumed that silicone caused the problem).
> > Flushing with alcohol also causes problems. BMW
> > brake systems should be flushed only with DOT 3 or
> > 4.
> >
> > If silicone is introduced into an older brake
> > system, the silicone will latch unto the sludge
> > generated by gradual component deterioration and
> > create a gelatin like goop which will attract more
> > crud and eventually plug up metering orifices or
> > cause pistons to stick. If you have already changed
> > to DOT 5, don't compound your initial mistake and
> > change back. Silicone is very tenacious stuff and
> > you will never get it all out of your system. Just
> > change the fluid regularly. For those who race using
> > silicone fluid, I recommend that you crack the bleed
> > screws before each racing session to insure that
> > there is no water in the calipers.
> >
> > New developments
> >
> > Since DOT 4 fluids were developed, it was recognized
> > that borate ester based fluids offered the potential
> > for boiling points beyond the 446F requirement, thus
> > came the Super DOT 4 fluids - some covered by the
> > DOT 5.1 designation - which exhibit a minimum dry
> > boiling point of 500F (same as silicone, but
> > different chemistry).
> >
> > Additionally, a new fluid type based on silicon
> > ester chemistry (not the same as silicon) has been
> > developed that exhibits a minimum dry boiling point
> > of 590F. It is miscible with DOT 3-4 fluids but has
> > yet to see commercial usage.
> >
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