Cooling your brakes
Being from the east coast I've yet to encounter my brakes heating up enough to require pulling over to let them cool down, at least not that I know of. This summer/fall we're doing our first trip out ...
Forum Discussion
Automotive brakes using a sacrificial material (friction material, both
disc and shoe) convert kinetic energy into heat.
That type of braking system has thermal dynamic attributes (laws of
physics) for each component and the sub-systems to the whole system
Thermal inertia (mass) and thermal rejection are the main elements of
managing the ultimate specification of that braking system. As are
the material specifications for each/all components (thermal conduction
rates, or impedance), efficiency of rejection, thermal performance
ranges, etc
Friction material is the main sacrificial component/material. The cast iron
is also, but to a lesser degree and dependent on the composition of
the friction material(s)
Heat generated at the point between the friction material and cast
iron will have that heat conducted to both the friction material and
cast iron. 'Some' of the heat is rejected by the outgases from,
mainly, the friction material
The out gas has a rate of conversion from solid to gas and the
rate of braking the key determination. FPM, PSI and a few
other attributes dictate that rate vs the friction material
composition/spec
That out gas rate can so high, that it will 'lift' the friction material
off of the cast iron and is the biggest portion of 'fade'. Why some
friction material will have slot(s) cut through them as escape
routs for those gases. Ditto cast iron slots and holes...out gas
escape routes
The more kinetic energy being dissipated, the more heat generated
Mainly rates of deceleration factored by stuff like speed, mass,
incline, etc. Meaning the harder you brake, the greater the amounts
of heat generated...ultimate temperature too. BTU and temp are two
different things in the same arena
Rejection (the removal or transferring of heat) has many components
and attributes to them
For our automotive brakes, ambient air is what we have as the recipient
for rejected heat. How it gets there and how much is the basics of this
topic
Very few disc brakes are solid rotored these days. Most are centrifugal
vaned rotors. RPM and tip swept dia are the main components of these fans.
The configuration of the vanes and the intake also throttle the rejection
rates
Some have more vanes, some have thicker vanes, some vanes are
straight, others curved.
Meaning that the faster the rotor spins, the more the centrifugal vanes
fling off air that has gone through the rotor innards to capture heat
Drilled rotors are mainly for track. Every day and especially when driven
HARD, has a rich history of cracking. Cast in holes do NOT have the
stress raisers that drilled holes do.
Slotted does not have as great a tendency to crack, as they do not
have the types of stress raiser that drilled holes do
Drilled holes and cast holes can have +40% reduction in material and
surface area, both detrimental to braking. Again, drilled holes are
mainly for track usage
Both holes and slots main function is to allow outgasses to NOT float
the friction material off of the mating cast iron surface
The other types of braking mentioned are good topics, but ancillary to
the OP's truck and application.
Now back to the OP's question and some of the very dangerous
advice...
First, this is a freebie forum and worth the price paid... I've taken an
extended break from this forum(s) and come back occasionally. Found
that too often was referencing Proverbs 26, verse 4...which applies to
several posts on this thread
The braking hard and coast to cool the brakes is the best, IMHO
By constantly holding or riding the brakes will NOT allow them to cool
down enough to become more efficient in rejecting the heat.
Temperature differential is the biggest component in the rates of heat
rejection. Why allowing the brakes to cool so important.
There is much, much more, but think this is the gist of it for this point
in this thread
Am also assuming within the OEMs ratings for your TV, the truck is
in good order and that you are not speeding...
disc and shoe) convert kinetic energy into heat.
That type of braking system has thermal dynamic attributes (laws of
physics) for each component and the sub-systems to the whole system
Thermal inertia (mass) and thermal rejection are the main elements of
managing the ultimate specification of that braking system. As are
the material specifications for each/all components (thermal conduction
rates, or impedance), efficiency of rejection, thermal performance
ranges, etc
Friction material is the main sacrificial component/material. The cast iron
is also, but to a lesser degree and dependent on the composition of
the friction material(s)
Heat generated at the point between the friction material and cast
iron will have that heat conducted to both the friction material and
cast iron. 'Some' of the heat is rejected by the outgases from,
mainly, the friction material
The out gas has a rate of conversion from solid to gas and the
rate of braking the key determination. FPM, PSI and a few
other attributes dictate that rate vs the friction material
composition/spec
That out gas rate can so high, that it will 'lift' the friction material
off of the cast iron and is the biggest portion of 'fade'. Why some
friction material will have slot(s) cut through them as escape
routs for those gases. Ditto cast iron slots and holes...out gas
escape routes
The more kinetic energy being dissipated, the more heat generated
Mainly rates of deceleration factored by stuff like speed, mass,
incline, etc. Meaning the harder you brake, the greater the amounts
of heat generated...ultimate temperature too. BTU and temp are two
different things in the same arena
Rejection (the removal or transferring of heat) has many components
and attributes to them
For our automotive brakes, ambient air is what we have as the recipient
for rejected heat. How it gets there and how much is the basics of this
topic
Very few disc brakes are solid rotored these days. Most are centrifugal
vaned rotors. RPM and tip swept dia are the main components of these fans.
The configuration of the vanes and the intake also throttle the rejection
rates
Some have more vanes, some have thicker vanes, some vanes are
straight, others curved.
Meaning that the faster the rotor spins, the more the centrifugal vanes
fling off air that has gone through the rotor innards to capture heat
Drilled rotors are mainly for track. Every day and especially when driven
HARD, has a rich history of cracking. Cast in holes do NOT have the
stress raisers that drilled holes do.
Slotted does not have as great a tendency to crack, as they do not
have the types of stress raiser that drilled holes do
Drilled holes and cast holes can have +40% reduction in material and
surface area, both detrimental to braking. Again, drilled holes are
mainly for track usage
Both holes and slots main function is to allow outgasses to NOT float
the friction material off of the mating cast iron surface
The other types of braking mentioned are good topics, but ancillary to
the OP's truck and application.
Now back to the OP's question and some of the very dangerous
advice...
First, this is a freebie forum and worth the price paid... I've taken an
extended break from this forum(s) and come back occasionally. Found
that too often was referencing Proverbs 26, verse 4...which applies to
several posts on this thread
The braking hard and coast to cool the brakes is the best, IMHO
By constantly holding or riding the brakes will NOT allow them to cool
down enough to become more efficient in rejecting the heat.
Temperature differential is the biggest component in the rates of heat
rejection. Why allowing the brakes to cool so important.
There is much, much more, but think this is the gist of it for this point
in this thread
Am also assuming within the OEMs ratings for your TV, the truck is
in good order and that you are not speeding...
