The sound of screeching tires may be one of the most annoying things you get to hear on the streets. However, for some people, the violent screech of tires and the nauseous whiff of brake fluid can mean something totally different: that their brakes are doing their job of keeping passengers safe from a collision.



Brakes are devices that are used to slow rotating wheels until they stop. Friction brakes are the most common examples of such brakes. Brakes like the ones used on everyday vehicles such automobiles, bicycles, trucks and trains use friction between brake pad and a wheel to slow the motion of a vehicle.

However, the friction created by the brakes generates a great deal of heat. The brake system should be able to dissipate this heat or else the brake could lose its efficacy.

There are many kinds of brakes ? the most common of which are the ones used in automobiles: the disc and drum brakes. Both, however, rely on hydraulics, or the use of brake fluid pressure to activate the brakes.

The drum brakes work by the constriction of brake shoes installed on the inside of the wheel. The friction generated by this action slows the motion of the vehicle.

The disc brake works by clamping the rotors of the wheel itself. Disc brakes are superior to drum brakes due to the fact that disc brakes are not prone to malfunction even when wet or immersed in water. This malfunction is called brake fade. Disc brakes can also handle higher braking temperatures and dissipate heat more quickly. Also, disc brakes do not trap water as drum brakes can.

In 1985, the first antilock brake system (ABS) was introduced for motor vehicles in the United States. ABS works as a safety feature to give drivers more control when braking. ABS has a microprocessor and individual wheel-speed sensors that monitors the brakes of a vehicle. The hydraulic control valves for each brake circuit prevent skidding during panic stops or when braking hard on wet or slippery surfaces. By 1990, ABS was available on about 25 percent of all new cars and trucks. Today, ABS is available on over 90 percent of all new vehicles.

Other Braking Systems

In 1869, George Westinghouse invented a different system of applying brakes. Instead of using liquid pressure to apply the brakes, he used a system wherein it is the air pressure that prevents the brakes from applying.

This is helpful since the Achilles heel of hydraulic brakes is that when there is a loss of pressure, the brakes become ineffective. In Westinghouse's system, when there is loss of air pressure, the brakes automatically apply.

This is a safer alternative that is useful in high-load transportation such as trains.

Large, heavy-duty trucks, as well as buses and trains, use compressed air pressure rather than hydraulic fluid to operate their brakes.

Tomorrow's Brakes

While we still mostly rely on friction for braking, many technological advances call for new braking methods.

For example aircraft also use spoilers, and flaps to slow its velocity through the air.

Electric cars and other electric vehicles use drum and disc brakes to stop, but some vehicles also make use of magnetic brakes, which create opposing magnetic fields to resist motion. This type of braking is called regenerative braking. This technique recaptures some of the vehicle's momentum as electrical energy. Regenerative braking uses the magnets within the electric motor itself to slow the vehicle. When the driver releases the accelerator pedal, the electric motor changes into a generator, thus recapturing the energy from the moving car and transforming it back into electricity

As transportation becomes faster, safety becomes a primary concern. More powerful means of controlling speed are needed, and the evolution of braking systems is not far off.