yhteensopivuus, jarrunesteet DOT 4 ja 5

minun lukemieni tekstien mukaan on niin että jos
vaatimus on DOT4, niin DOT5 on vielä parempaa.
Sitä ei vaan oltu "keksitty" silloin kun se DOT4
vaatimus on otettu käyttöön!
Dot4 or better...

...jarrunesteissä on muutenkin eroja
ominaisuuksissa! En nyt muista minkälaisia mutta
esim DOT 5 ei välttämättä ole DOT 4 parempi..
Tärkein nyt on ettet mene sekoittamaan...!!!

Automotive brake fluid has many
responsibilities. Corrosion protection and
lubrication of brake system components are
only a portion of the role brake fluid must play.

All automobiles that have a hydraulic braking
system must use brake fluid in order for the
brake system to operate. The type of fluid
used can depend on the type of vehicle and
the demands of the vehicles brake system.

The two most common brake fluids used in
the automotive industry are fluids that contain
Polyalkylene Glycol Ether and fluid that
contains Silicone or Silicium-based Polymer.
Both Fluids are common but very different in
regards to the manner in which they perform.
Fluids containing Polyalklene Glycol Ether are
more widely used and are the only fluids that
should be used in racing brake systems.

Because brake systems may reach extreme
temperatures brake fluid must have the ability
to withstand these temperatures and not
degrade rapidly.

SILICONE BASED FLUID
Fluids containing Silicone are generally used
in military type vehicles and because Silicone
based fluids will not damage painted surfaces
they are also somewhat common in show
cars.

Silicone-based fluids are regarded as DOT 5
fluids. They are highly compressible and can
give the driver a feeling of a spongy pedal. The
higher the brake system temperature the
more the compressibility of the fluid and this
increases the feeling of a spongy pedal.

Silicone based fluids are non-hydroscopic
meaning that they will not absorb or mix with
water. When water is present in the brake
system it will create a water/fluid/water/fluid
situation. Because water boils at
approximately 212º F, the ability of the brake
system to operate correctly decreases, and
the steam created from boiling water adds air
to the system. It is important to remember that
water may be present in any brake system.
Therefore silicone brake fluid lacks the ability
to deal with moisture and will dramatically
decrease a brake systems performance.

POLY GLYCOL ETHER BASED FLUIDS
Fluids containing Poly glycol ethers are
regarded as DOT 3, 4, and DOT 5.1. These
type fluids are hydroscopic meaning they have
an ability to mix with water and still perform
adequately. However, water will drastically
reduce the boiling point of fluid. In a
passenger car this is not an issue. In a
racecar it is a major issue because as the
boiling point decreases the performance
ability of the fluid also decreases.

Poly glycol type fluids are 2 times less
compressible than silicone type fluids, even
when heated. Less compressibility of brake
fluid will increase pedal feel. Changing fluid
on a regular basis will greatly increase the
performance of the brake system.

FLUID SPECIFICATIONS All brake fluids must
meet federal standard #116. Under this
standard is three Department of
Transportation (DOT) minimal specifications
for brake fluid. They are DOT 3, DOT 4, and
DOT 5.1 (for fluids based with Polyalkylene
Glycol Ether) and DOT 5 (for Silicone based
fluids).

MINIMAL boiling points for these
specifications are as follows:

 
  Dry Boiling Point Wet Boiling Point
DOT 3 401ºF 284º F

DOT 4 446º F 311º F
DOT 5 500º F 356º F
DOT 5.1 518º F 375º F

Racing brake fluids always exceeds the DOT
specifications for dry boiling points. Wet
boiling points generally remain the same.

DOT 3 VS. DOT 4 and 5.1
AFCO's 570º brake fluid is a DOT 3 type fluid.
However, it has a dry boiling point that is 52º
higher than DOT 5.1 specifications, 124º
higher than DOT 4 specifications and 169º
higher than DOT 3 specifications. AFCO's
570º fluid meets or exceeds all DOT 3, 4, and
5.1 lubrication, corrosion protection and
viscosity specifications.

AFCO's 570º racing fluid meets but does not
exceed federal standards for wet boiling point
specification; therefore, its classification is
DOT 3. Because AFCO's 570º fluid is intended
for use in racing type brake systems that
undergo frequent fluid changes, exceeding
federal standards for wet boiling points is of
little concern. Racing brake fluids always
exceeds the DOT specifications for dry boiling
points. Wet boiling points generally remain the
same.

WET VS. DRY BOILING POINT
The term boiling point when used regarding
brake fluid means the temperatures that brake
fluid will begin to boil.

WET BOILING POINT
The minimum temperatures that brake fluids
will begin to boil when the brake system
contains 3% water by volume of the system.

DRY BOILING POINT
The temperatures that brake fluid will boil with
no water present in the system.

MOISTURE IN THE BRAKE SYSTEM
Water/moisture can be found in nearly all
brake systems. Moisture enters the brake
system in several ways. One of the more
common ways is from using old or
pre-opened fluid. Keep in mind, that brake
fluid draws in moisture from the surrounding
air. Tightly sealing brake fluid bottles and not
storing them for long periods of time will help
keep moisture out. When changing or
bleeding brake fluid always replace master
cylinder caps as soon as possible to prevent
moisture from entering into the master
cylinder. Condensation, (small moisture
droplets) can form in lines and calipers. As
caliper and line temperatures heat up and
then cool repeatedly, condensation occurs,
leaving behind an increase in moisture/water.
Over time the moisture becomes trapped in
the internal sections of calipers, lines, master
cylinders, etc. When this water reaches 212º F
the water turns to steam. Many times air in the
brake system is a result of water that has
turned to steam. The build up of steam will
create air pressure in the system, sometimes
to the point that enough pressure is created to
push caliper pistons into the brake pad. This
will create brake drag as the rotor and pads
make contact and can also create more heat
in the system. Diffusion is another way in that
water/moisture may enter the system.

Diffusion occurs when over time moisture
enters through rubber brake hoses. The use
of hoses made from EPDM materials
(Ethlene-Propylene-Diene-Materials) will
reduce the amount of diffusion OR use steel
braided brake hose with a non-rubber sleeve
(usually Teflon) to greatly reduce the diffusion
process.

THINGS TO REMEMBER
Brake fluids dry boiling point is more
important then wet boiling point when used in
a racing brake system.
Passenger cars very rarely will undergo a
brake fluid change making the wet boiling
point more important.
Racing brake system fluid is changed often
and a system with fresh fluid will most likely
not contain water.
Because of this, racers should be concerned
with the dry boiling point.
Racing fluid exceeds DOT 3, 4, and 5.1 dry
boiling point specifications.
Never use silicone based fluids in racing
brake systems.
Using racing brake fluid will increase
performance of the braking system.
Never reuse fluid. º Never mix types or brands
of brake fluid.
Use smaller fluid containers that can be used
quicker.
If fluid remains in container be sure to tightly
seal and do not store for long periods of time.
Purge system (complete drain) and replace
fluid often.
Immediately replace master cylinder reservoir
cap following any maintenance.

Eri tyyppisiä nesteitä ei saa sekoittaa keskenään.

Glykolieetteripohjaisen DOT 3 ja 4 nesteen
haittana on hydroskooppisuus, eli ne imevät
ilmasta kosteutta itseensä, joka tiivistyy
vedeksi ja siten alentaa nesteen kiehumispistettä.

Silikoniöljypohjaisen DOT 5:n etuna on se, ettei
se ole hydroskooppinen. Haittana on kuitenkin
että sen kokoonpuristuvuus on suurempi ja
voitelevuus huonompi. Veden sekoittuminen tähän
tyyppiin (esim. seassa DOT 4, joka imee kosteutta
ilmasta) on erittäin kriittistä, koska
varsinaisen DOT 5 -nesteen lämmetessä yli veden
(tai veden ja DOT 4:n seoksen) kiehumispisteen,
veden kiehuminen aiheuttaa höyrynmuodostusta ja
jäätyminen vastaavasti jääkiteitä. Höyrykuplat
käyttäytyvät ilmakuplien tavoin puristuen kokoon
ja aiheuttaen jopa jarrujen häipymisen. Jääkiteet
luonnollisesti voivat tukkia jarruputket. Lisäksi
glykolieetteripohjaiselle nesteelle suunnitellun
järjestelmän kumiosat eivät välttämättä kestä
silikoniöljypohjaista nestettä (huono
voitelevuus).

DOT 5 ei sovellu sekoitettavaksi DOT3 ja DOT4 nesteen kanssa!!

Mutta DOT 5.1 soveltuu. Onko noiden hinnassa suurtakaan eroa, joten jos vaihtaa nesteen, eikö kannata laittaa DOT 5.1 ?
Ei tule ainakaan sekoituksen kanssa ongelmia.
En oikein tiedä, missä sitä DOT5 nestettä käytetään?