ABS brakes: what they are, how they work and how to detect faults

El ABS braking system It is one of the greatest safety inventions in automotive history. In fact, together with the airbag and the seat belt, it is known as one of the items that have saved the most lives since its introduction in cars, but what are ABS brakes? How do they work? What are the faults of the ABS brakes? We are going to discover everything about this element that we will probably never realize its existence.

The acronym ABS responds to the name, in German, of Anti-lock braking system, although we commonly know it by the English Anti-Lock Brake System. In Spanish this is the anti-lock braking system and, although its appearance or its first patents date from the beginning of the last century, the reality is that its application to the car would not usually arrive until the second part of it. Today it is a mandatory system in many places, including the European Union, where it is mandatory for new cars marketed within it since July 1, 2004.

What is ABS?

ABS is a system that simply prevents the brakes from locking the wheel. When we brake, pressure is exerted on the brakes that can exceed the tire's adherence limit and, therefore, we will block the wheel, losing braking power, lengthening it and losing ability to steer the car. ABS eliminates this man-machine interaction fault automatically.

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Through different sensors that detect the angle of rotation of the wheels, the speed or the power of the braking, the system plays with the pressure of the braking circuit to dose the power we exert on the pedal and thus avoid blockage. In other words, by making small automatic corrections in brake pressure prevents the locking point of the wheels.

What factors intervene in braking with ABS?

As in everything, there are many factors that intervene when the ABS system works or not. One of them and perhaps the most important is the tire condition. If the tires have incorrect pressure to tires are worn or crystallized, its grip limit is reduced and, therefore, the anti-lock system works more than necessary and inefficiently. The condition of the brakes themselves is also a decisive factor, as is the condition of the pads or of the disks.

However, another of the most determining factors in its operation is the state of the road. The ABS system is not always effective, for example when the road is very slippery: snow, mud, ice, dirt. The anti-lock in these cases tends to go a little crazy because the wheel constantly locks up. Braking slows down, but the distance can be multiplied.

ABS brakes on wet roads can do wonders. The limit of adhesion is reduced and through continuous adjustment of the braking power the braking distance can be reduced. And what is more important, by not locking the wheels, we do not lose control of the car, so we can continue braking without so much fear that the car will whiplash or spin because we have locked the wheels. In curve this the crucial.

How do I know when it works?

Not all ABS systems work the same way, but they do have a common component. In any case, they have been refined to improve their performance and so that the driver barely notices their intervention. It is not advisable to try just to try for a simple reason, the ABS usually works in emergency braking and, therefore, the fact that this element is activated always carries a danger.

The driver, when the ABS activates, will notice how the pedal starts to vibrate strongly at the same time it will lose sensitivity. Two things can happen to the ear, that a warning beep sounds, and that we hear a kind of saw sound (clack-clack-clack). On the dashboard, on the control panel, in some cars the warning light can come on, but it is not usual.

In any case, as it is usually something punctual, probably in the situation in which it is activated we will not have time to listen to brake sounds or witnesses. Sometimes cornering or braking on a bump can activate the system momentarily. no need to panic if we notice it, on the contrary, we have to let the electronics work.

Does my car have ABS?

A new car purchased in the European Union as of July 1, 2004 It has ABS anti-lock system. But sometimes we buy before that date or on the second-hand market. The ABS has been something relatively common before the aforementioned date, but not all manufacturers had the obligation to mount it. Sometimes having or not having ABS could be a matter of the version or finish chosen.

To find out if my car has ABS, the simplest thing, if there is no anomaly, is to turn on the ignition and see how the associated warning light comes on usually for a few seconds. It is a kind of check to see if the system is active and working properly. If it doesn't turn on it may be because our car doesn't equip it. In any case, the most sensible thing is to go to a dealer/workshop of our brand to ask or look at the user manual.

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What happens when it fails?

Each car or each manufacturer has a type of warning, in addition to the warning light, which warn of a malfunction of the element. For example, some cars place a text message with the bug.

What must be completely clear is that the fact of having an ABS malfunction does not mean that our car has run out of brakes. That is, we will circulate without the anti-lock but the brake system will continue to work correctly. In fact, we will not notice anything beyond a warning or a more than probable blockage in an emergency situation.

In many cars, the brake distributor has been replaced by an electronic system that works together with the ABS. That is why in strong braking if the system fails we can block the rear wheels, especially in cars prepared to carry cargo such as pick-ups, vans or family.

On the other hand, ABS is the mother system of many other electronic systems, so a failure of this alters the operation of the ESP, the traction control and even the hill start assist system. Everything that ultimately controls the turning of the wheels.

It must be taken into account that not all the warning lights that may come on related to the brakes have to do with the anti-lock. In plain words, if what comes on is the brake fault light, the fault will be there, and not in the ABS. It is very recurrent that the warning light comes on low level in for brake fluid or worn pads and the user confuses it with ABS. Moreover, if the ABS fails in the warning light that lights up, the acronyms will appear.

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What can go wrong with ABS brakes?

As we said before, the system is based on multiple sensors, and as you can already guess, they are the most likely to fail. Although an ABS fault is not very common, it can fail this sensor system and fail. On the other hand, and more complicated economically, it may be that the car's control unit is failing.

To find out with greater certainty, you have to connect the car to a diagnosis to determine the origin of the fault. Wiring can be yet another factor in a malfunction.

To add to the list of possible brake faults, it may be a simple fuse that fails. Without going any further, in current vehicles most of the time the ABS disconnection can only be carried out by means of the fuse removal. But be careful, not only do you have to trust the witness, because the light bulb that illuminates the painting may be burned out. That is why it is worth checking if it works in the check that we carry out when giving the contact. Attention, because even though both systems coexist and work together, a failure of the ESP stability system will be noted on the dashboard with its own symbol.

What is not an ABS fault?

Earlier we mentioned that there was no need to confuse an ABS failure with a brake system failure. That is why we must trust the witnesses. If we do not do it, we must take into account this series of issues that do not mean a malfunction of it. For example, when we brake and notice that the pedal goes down the safest thing is that we have air in the circuit or the brake master cylinder is connected. It has nothing to do with anti-blocking and this does entail a more serious danger to our security.

On the other hand, the opposite may happen, that we step on the brake pedal, it is very hard and we have to apply a lot of pressure to stop it. In this case it is most likely that the brake servo is failing. To check it, it will suffice to press the brake repeatedly with the engine stopped until it becomes hard and, without letting go of it, start the engine. If the fault is not smoothed out it is almost clear. In turbo engines, the vacuum pump or the vacuum lines to the brake booster may fail.

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It can also happen, and perhaps it can be confused with ABS, that the car brakes on one front wheel and another opposite rear. This is because many cars mount an X safety circuit to ensure minimal braking on both axles. Again, it has nothing to do with the ABS, and more with air in the circuit or a direct leak in one of them.

Additionally, if when braking more or less hard we notice that the car vibrates but does not make a strange noise or that we are not used to hearing, it will not have anything to do with the ABS either. And I notice in capital letters what “the car vibrates”. When the ABS acts it is the pedal that we notice vibrate. If not, surely we have the unbalanced wheels, warped discs or bearings in poor condition. If when braking the car tends to go to one side, it could be a bad tire pressure, the imbalance of braking due to worn brakes or a direction not aligned.

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Is it worth disconnecting the ABS?

No, absolutely not. It's more, few are the cars in which the ABS is deactivatable. We can disconnect the traction or stability systems, but the ABS is always there. It is such a highly developed system and one in which we drivers must trust so much that it's not worth doing without. Some ATVs with their mud, snow, or gravel modes may adjust their operation to allow lockup.

It is true that sometimes it is more of a nuisance than an advantage, but those situations are rare. On highly slippery surfaces it goes crazy trying to slow down the car and, in turn, it might be better to block the wheels so that the tire digs into the surface in search of greater grip. Many times is the ESP system the one that behaves more negatively on very slippery surfaces, making the anti-lock work constantly.

In any case, it is not recommended to disable it in these circumstances either. In the following video you can see how a car behaves without ABS on slippery terrain.: asymmetric braking. The slight difference in grip between the wheels on one side and the other causes the car to go out of its path if it does not have ABS (which ESP can also help).

Why is ABS not used in competition?

The ABS itself has been used even in high competition. We refer, for example, to formula 1. But as you know the regulations have prohibited, rather they prohibited many years ago, a good number of electronic systems such as traction control or active suspension. The ABS is another of those elements that are not available by regulation.

But one of the most powerful reasons why it is not used regularly in competition is because the rider loses sensitivity under heavy braking. Stop feeling when a wheel reaches its grip limit. In fact, as the races take place in safe environments, the drivers themselves can do the anti-lock functions manually with their foot, and that is why we can see large blocks in a rush of braking in high competition.

Images 2, 4 and 6 – Christine und Hagen Graf, William Clifford, David Howard

More information about this model

H

• Plazas 5
• Power 150 - 201 hp
• Consumption 5,3 - 8,6l/100km
• Assessment 4