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.

Auto service and repair for: Audi, BMW, Mercedes, Land Rover, Lexus, Jaguar, Porsche, VW, Volvo, Saab, and more. Servicing cars from the Dallas, Plano, Richardson and the DFW Metroplex area.