ABS

The ABS, as it is commonly called is the abbreviation for Anti-Lock Braking System. This is a feature that many of the newer cars come fitted with. But it was not always the case, and still is not the case with several makes.

What is the ABS? Before that question is answered, it is perhaps necessary to look at the "brakes". But simply, a brake is a system device that reduces speed or stops a moving object (in this case your car) by creating a force in the opposite direction.

Insufficient pressure (brake torque) in the brake system causes "wheel lock" while the vehicle is moving above 80 km/h on a dry paved road surface. Premature "wheel lock" occurs from turbulent shock waves being generated by the uneven braking surfaces (rotors or drums contacting the pads/shoes), vibrating or slapping against the hydraulic pistons in either the clippers or the wheel cylinders.

The force of these shock waves can be easily 100 times that of brake torque or the maximum pressure exerted on the rotating brake components. These shock waves have more than enough force to lock the wheels.

Wheel lock occurs when brake torque forces exceed tyre grip forces. The impact would be much greater if the road surface is slippery due to rain, oil spills or other causes, or if the vehicle is driven at great speed.

At speed, control of the car is difficult, especially at corners where there is a tendency to skid. Statistics show that approximately 40% of automobile accidents are due to skidding. These problems commonly occur on vehicles with the conventional brake system, without the added device called the ABS.

The ABS absorbs the unwanted turbulent shock waves, and modulates the pulses thus permitting the wheel to continue turning under maximum braking pressure. The device "limits the degree of wheel slip of one or more of the wheels of the vehicle".

This control permits the driver to steer away from any type of collision as long as there is friction between the tyres and the road surface.

Installing the ABS will permit a vehicle to stop more quickly, keep it under control, with wheel slip being limited such that steering is possible during emergency stops. The ABS will limit that degree of slip until the coefficient of friction on the road surface approaches ZERO. Yet, the device will modulate pressure and keep the vehicle straight, if the brake pressure is applied reasonably.

ABS was originally invented to help aircraft with their landing procedures. Later, the system was adapted for use in automobiles. But only a few of the manufacturers employed this device, mainly because of the high cost. Only luxury class cars like the Mercedes Benz, BMW and Audi (all German) fitted ABS.

By the mid 80s an American automobile manufacturer developed a mechanical ABS. Later came the gaseous ABS. Prices too dropped to affordable levels. Now they are increasingly being fitted as standard equipment in cars.

However, a recent study by the American Insurance Institute for Highway Safety has shown that cars with ABS are more likely than those with conventional devices to become involved in crashes that are fatal to their occupants.

Researchers at the Institute conducted their studies on various types of crashes - single-vehicle, multiple-vehicle, rollovers and those in which cars ran off the road.

It found that the greatest increase in the incidence of crashes fatal to occupants of anti-lock braking system cars occurred in single-vehicle impacts.

An Institute spokesman concluded that the findings added to evidence that anti-locks were not producing overall safety benefits. But it remained unclear why anti-locks are not producing the benefits most people expected.

One explanation has been that drivers, feeling over-confident, could have been driving faster, or could be pumping the brakes or failing to hit the brake pedal with sufficient force.

Another possible cause could be an easing off on the brakes, which deactivates the anti-lock mechanism. Anti-lock brakes rely on sensors to determine when a wheel is about to lock up, which can cause loss of traction or skidding.

Researchers remind owners of vehicles with the ABS that the anti-lock brakes should not be pumped, as drivers have been traditionally taught to do in emergencies. Drivers would have to unlearn past braking habits and keep hard, continous brake pressure instead.*

http://www.autostation.com/ccc/abs.html

The Dos And Don'ts of Anti-Lock Brake Systems

Four-wheel ABS is a safe, effective braking system when used properly. It offers an important safety advantage by preventing the wheels from locking during emergency braking situations, allowing drivers to maintain control over steering and operate vehicles more effectively. To take full advantage of the maximum safety benefits, drivers must learn how to operate their anti-lock braking systems correctly.Do keep your foot on the brake. Maintain firm and continuous pressure on the brake to enable four-wheel ABS to work properly. Avoid pumping the brake, even if the brake pedal is pulsating. In light trucks that are equipped with rear-wheel anti-lock brakes, however, the driver should apply the brake pedal with just enough force to stop the vehicle without locking the front wheels. The driver can then maintain steering control while the rear-wheel anti-lock prevents the vehicle from skidding sideways.Do allow enough distance to stop. Follow three seconds or more behind vehicles when driving in good conditions. Allow more time if conditions are hazardous.Do practice driving with ABS. Become accustomed to pulsations that occur in the brake pedal when ABS is activated. Empty parking lots or other open areas are excellent places to practice emergency stops.Do consult the vehicle's owner's manual for all additional driving instructions on the anti-lock brake system.Don't drive an ABS-equipped vehicle more aggressively than vehicles without ABS. Driving around curves faster, changing lanes abruptly or performing other aggressive maneuvers is neither appropriate nor safe with any vehicle.Don't pump the brakes. In four-wheel ABS-equipped vehicles, pumping the brake turns the system on and off. This decreases braking efficiency and increases stopping distance. ABS pumps the brakes for you automatically at a much faster rate and allows better steering control.Don't forget to steer. Four-wheeled ABS enables drivers to steer in emergency braking situations, but t!

he system itself does not steer.Don't be alarmed by mechanical noises and/or slight pedal pulsations while applying the brake in an ABS-equipped vehicle. These conditions are normal and let the driver know ABS is working.

http://www.abs-education.org/abcs/abcindex.htm

What Your Anti-Lock Brakes Do ABS can improve vehicle stability, steerability and stopping capability. Four-wheel ABS prevents wheel lock-up, allowing drivers to maintain stability as well as steering control during an emergency braking situation.

How the Anti-Lock Mechanism Works When a driver operating a four-wheel ABS equipped vehicle steps firmly on the brake pedal, the system automatically modulates the brake pressure at all four wheels, adjusting pressure to each wheel independently to prevent wheel lock-up. With four-wheel ABS, the driver has improved steering control of the vehicle.

The Difference Between Four-Wheel and Rear-Wheel Anti-Lock Brakes Four-wheel ABS is designed to maintain vehicle stability and improved steerability in emergency stopping situations. Because the braking system in a four-wheel anti-lock equipped vehicle modulates the braking pressure, preventing wheel lock on all four wheels, the driver has improved control over steering.

Rear-wheel anti-lock brakes, found exclusively on light trucks, vans and sports utility vehicles, prevent wheel lock of the rear wheels only. This allows the driver to maintain directional stability and prevents the rear end of the vehicle from skidding sideways. The front wheels can still lock up on rear-wheel ABS systems just like conventional brakes. If that happens, the driver should ease up on the brake pedal with just enough pressure to allow the front wheels to start rolling again, so the driver can steer.

How to Know when Your ABS Is Working Most anti-lock brakes let you know when you have activated your ABS. The driver can notice a mechanical sound and feel some pulsation or increased resistance in the brake pedal. It is important to keep your foot on the brake pedal when you hear noise or feel vibrations. Continue to apply firm pressure.

By the end of the year 2000, about one in three passenger vehicles in the United States and Canada were equipped with anti-lock braking systems(ABS).

ABS was first developed and patented in 1936 and is derived from the German term antiblockierysystem.

Anti-lock braking systems have sensors near each wheel which monitor rotational speed to determine when the wheels are about to lose traction and lock. The electronic control unit monitors these signals and sends commands to the hydraulic control unit to modulate brake pressure in order to prevent wheel lock.

ABS pumps the brakes at a rate of up to 18 times per second, allowing drivers to maintain some steering ability.