The Dry Boiling Point is the temperature
at which a brake fluid will boil in its virgin non-contaminated
state. The highest temperature Dry Boiling Point available
in a DOT 3 fluid is 572° F.
The Wet Boiling
Point is the temperature a brake fluid will boil after
it has been fully saturated with moisture. The DOT 3
requirement for wet boiling point is a minimum temperature
of 284° F.
There are many ways for moisture
to enter your brake system. Condensation from regular
use, washing the vehicle and humidity are the most common,
with little hope of prevention. Glycol based DOT 3 &
4 fluids are hygroscopic; they absorb brake system moisture,
and over time the boiling point is gradually reduced.
Wilwood does not recommend using DOT 5 fluid
in any racing applications. DOT 5 fluid is not hygroscopic,
so as moisture enters the system, it is not absorbed
by the fluid, and results in beads of moisture moving
through the brake line, collecting in the calipers.
It is not uncommon to have caliper temperatures exceed
200° F, and at 212° F, this collected moisture
will boil causing vapor lock and system failure. Additionally,
DOT 5 fluid is highly compressible due to aeration and
foaming under normal braking conditions, providing a
spongy brake feel. DOT 5 fluid is best suited for show
car applications where its anti-corrosion and paint
friendly characteristics are important.
Whenever
you add fresh fluid to your existing system (never mix
fluids of different DOT classifications), it immediately
becomes contaminated, lowering the boiling point of
the new fluid. For maximum performance, start with the
highest Dry Boiling Point available (try Wilwood’s Hi-Temp°
570 Racing Brake Fluid), flush the system completely,
and flush it regularly, especially after severe temperatures
have been experienced. |
