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Brake System
Looking at it from a scientific point of view, automobile brakes
convert kinetic energy or the forward momentum of your car into thermal
energy.
If you’ve ever watched a nighttime road race you’ve seen
the brakes of the racecars glowing a very noticeable red as they
slow for a corner. That will give you some idea of the heat that
brakes generate… although normal driving does not produce temperatures
that extreme.
Now that we know the scientific principle involved, let’s consider
how brakes impact (pun intended) your driving. Worse case scenario…your
brakes fail – you hit something. Or worse yet - somebody. That
simple fact makes brake maintenance most important.
Typically, when you apply your brakes you initiate a stopping force
ten times as powerful as the force that puts your vehicle in motion.
Your brakes can exert as much as 1,000 pounds of hydraulic pressure
on each of the four brakes…with that kind of pressure involved
it’s no wonder that hydraulic lines carrying brake fluid can
sometimes spring a leak.
In today’s cars the master cylinder usually has a power-assist
feature that activates both front and rear brakes. And, they act
independently of each other so if one fails; the other can provide
adequate braking power. Safety systems are designed into contemporary
braking systems in an attempt to increase their reliability.
Getting back to our racecar example, many of today’s vehicles
sport disc brakes, which were originally developed for racing. It
is common however for a car to have disc brakes on the front wheels
and conventional drum brakes in the rear. Incidentally, the parking
brake is a cable-operated system, which traditionally operates the
rear brakes.
In almost all braking systems, the brake pedal is connected to a “master
cylinder” by a push rod. The master cylinder connects to each
wheel’s brake cylinders via steel brake lines and flexible
rubber hoses. The entire hydraulic system is filled with a special
brake fluid, which is forced through the system by the movement of
the master cylinder pistons. As noted, this fluid is under exceptional
pressure so if you begin to notice a leak of some sort under your
car, it’s wise to check it out quickly. Brake fluid leaks,
along with engine oil, power steering and transmission leaks can
prove to be expensive if not dealt with promptly.
The front disc brakes use friction “pads” which are housed
in “calipers”. The pads are forced against machined surfaces
of a rotating disc called the “rotor”. The rear brakes
are frequently of the “drum” type. In this brake technology,
there are internal expanding brake “shoes” which are
forced against the inside machined surface of a rotating drum. Whether
it’s disc or drum, the heat producing friction is what brings
the vehicle to stop.
Contemporary disc brakes, due to their lighter weight and better
performance, are the solid choice over drum brakes. The greatest
advantage of disc brakes is that in routine driving they are essentially “fade” free.
That is, repeated application does not result in excessively high
temperatures developing in the linings and drums, which tends to
lower the brake’s stopping power.
For some time now “anti-lock” brake systems, (also known
as ABS brakes) have been available. This brake enhancement device
prevents wheels from locking up, thereby throwing the car into a
skid. When the system senses that one or more of the vehicle’s
wheels are rotating considerably slower than the others (a condition
that will cause a wheel to lock) it moves the valves to decrease
the pressure on the braking circuit, effectively reducing the braking
force on that wheel and causing a characteristic pulsing feel through
the brake pedal. This reduces stopping distance and importantly,
allows the driver to maintain steering control. Incidentally, the
pulsing sensation is not noticed until the ABS system kicks in – something
that typically doesn’t happen in normal driving. Thus, when
it does happen, it can catch most drivers off guard.
As you might imagine, regardless of brake type, parts designed to
intentionally rub against other parts without a lubricant must wear
over time. So, the trick is to perform regular brake system checks
to insure brake pads and shoes are not wearing beyond their design
limits as to do so, will damage adjacent parts of the braking system
resulting in expensive repairs.
In summary, keep an eye on your brake fluid…owner’s manuals
provide information on where the brake fluid reservoir is located
under the hood. Note too that there are different types of brake
fluid. Again, consult your owner’s manual for specifications.
And have your brakes checked on a regular basis. At Dallas Auto Sports
we, along with most manufacturers, recommend a system check every
10,000 miles or six months. To schedule an appointment, stop and
give us a call at 214.320.2228.
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