ABS - Anti Lock Braking System - Queries


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Re: ABS - Anti Lock Braking System - Some Queries

It has a 4 channel ABS with EBD. (EBD requires a 4 channel ABS, will not work with 3 channel ABS, since it requires monitoring of all the 4 wheels).

Having discs or drums does not determine whether ABS is 3 channel or 4 channel.

For example, electronic aids like TCS (Traction Control System) and EBD (Electronic Brake Force Distribution) are advanced forms of ABS. All cars will TCS and EBD compulsorily requires a 4 channel ABS as TCS and EBD requires monitoring of all 4 wheels, which only a 4 channel ABS can do.

They are outsourced - most probably Bosch or Delphi.
Also went back to the brochure of my car once again, saw it has EBD irrespective of "Ventilated Disc" and "Drum" in the front or rear - so it will have a 4 channel ABS.

Answers are below each of your questions. Hope that clarifies.
Yeah, now i am much better off with the understanding.

Thank god, i was running another thread, asking whether tyre uprgade is necessary. Would put that on hold then.

Thanks so much to all, who has clarified things for me.
 
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Re: ABS - Anti Lock Braking System - Some Queries

Also went back to the brochure of my car once again, saw it has EBD irrespective of "Ventilated Disc" and "Drum" in the front or rear - so it will have a 4 channel ABS.
Correct. If the Dzire has EBD, it will have a 4 channel ABS.
 
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Re: ABS - Anti Lock Braking System - Some Queries

ABS - Anti Lock Braking System.

The ABS has two main components - wheel speed sensors which are attached on each wheel and an ECU.

Wheel speed sensors do the job of monitoring the wheels. If it detects any lock in the wheel, it sends a signal to the ECU that the particular wheel is locking and the ECU will immediately lessen the brake pressure on that wheel for it to stop skidding. When the wheel starts rolling again, it again increases the brake pressure on the wheel. Again the wheels will tend to lock and the ECU will lessen the brake pressure. This happens very very fast, so you wont feel the pumping happening. You will only feel a judder on your brake pedal.



Not necessary buddy. Punto has discs in the front and drums in the rear.

It has a 4 channel ABS with EBD. (EBD requires a 4 channel ABS, will not work with 3 channel ABS, since it requires monitoring of all the 4 wheels).



As explained by Mukesh, 3 channel ABS has 2 sensors on both the front wheels and 1 sensor on the rear axle. The disadvantage is that it cannot individually control one of the rear wheels. Whereas 4 channel ABS has a sensors on all the 4 wheels thereby individually controlling all the wheels independently.

Having discs or drums does not determine whether ABS is 3 channel or 4 channel.

For example, electronic aids like TCS (Traction Control System) and EBD (Electronic Brake Force Distribution) are advanced forms of ABS. All cars will TCS and EBD compulsorily requires a 4 channel ABS as TCS and EBD requires monitoring of all 4 wheels, which only a 4 channel ABS can do.

Fortuner comes with rear drum brakes, yet it has TCS and so it has a 4 channel ABS.

Safari comes with rear drum brakes and it has EBD and hence it will have a 4 channel ABS.

I hope I did not confuse you!



They are outsourced - most probably Bosch or Delphi.
Thanks for the correction Raj,during the fixation of ABS in my hawk, it was a cotech who passed me this info.
Now acknowledged the correct info.
 
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Although there is nothing more technical left to be explained here.Kudos to our forum mates for great explanation.So now let me try explaining all and everything in a simple or say 'DESI' language(all will be my personal observations)..:biggrin:
Before i come to the questions, let me state my understanding in brief.

Understanding
I understand that in nutshell ABS is a mechanism which prevents the wheels of your car to get locked in case of sudden and panic braking and therefore it allows you to steer the vehicle at the last moment, thereby avoiding a possible collision and also prevents your vehicle in skidding because the wheels are not locked.
100% correct.

Contrary to the popular myth that ABS results in reducing the braking distance, it actually elongates the effective braking distance of the vehicle, because the wheels are not getting locked.
This is partially correct.Actually it depends on the surface and load conditions.
Example:On an uneven surface or with some gravel on road.The ABS increases the braking distance and similarly if the vehicle is loaded with passengers and is going downhill then also ABS increases braking distance.But no issue as the vehicle is steerable.
I noticed this when I was descending a hilly road with seven passengers in my Innova and when I braked hard I noticed that the distance was longer than usual,in fact even that the ones without ABS too(my personal observation,can be wrong too).

Questions
1. I have heard and read, that ABS stops working at greater speeds (more than 80 -100 KM/hr). Is it true? If Yes, then why that is so?
ABS stops working only when the speed is below even 10 kph.Why?Because at those speeds the vehicle doesn't skid.
But on slippery surfaces where one wheel tends to lock and another not then ABS works at even 1 kph.

2. Also at the same time, I have read or heard that even at lower speeds (less than 20 - 25 Km/hr) ABS doesn't respond well and the driver need to really brake hard to put the vehicle to stop. If this is true, why is it so?
Weather the speed is 5* kph or 500 kph..the ABS will work.(*-Conditions apply)

3. When a driver, Panic brakes, it means that the driver wants the vehicle to stop immediately, but if ABS still allows the rolls in the wheels, then how it is effective?
Buddy when your wheels are locked that means you are in a nearly 'zero' grip situation,now however way you turn the wheel,the vehicle will skid freely in whatever direction it wants to skid.But with ABS,you will get that extra bit of grip which keeps your tyres rolling and hence you can use the steering wheel to change the direction of movement.It is very very useful while driving on steep hilly roads during rain or snowfall especially at the time of descending the steep slopes.

How ABS works?
Simple it is,you take four wheels and add sensors on them.
All these sensors are programmed in such a way that they send information 300(it can be 10,60,100 or even 1000 depending on the sensors) times per second to a central computer.
Now this computer is programmed in a way that this matches the tyre speeds and speed reduction etc etc.
Now in case you brake,the computer is working at 1/300th of a second and hence in that 1/300th parts it will keep on changing the brake force on each tyre and keep them rolling.

It something like when we apply brakes on our non-ABS equipped cars then we slowly apply the brake and as soon as the wheel locks we release the brake and apply it again.
In case of ABS,the computer does the same on all wheels 300 times per second.I hope you got the point now.
And yes,to feel the ABS working in any car what you need to do is:-
Accelerate the car till 140-150 kph and apply hard brakes.What you will notice is that the car will try to change its direction,in fact will try to move like a snake but won't do and secondly there will be very slight vibration in the whole car if you apply hard brake in an ABS equipped car at high speeds(My personal observation).

How ABS reduces braking distance?
Simple it is,best braking is obtained when the tyres are on the verge of locking.Or say its the condition in which even very very minute addition in brake force locks the wheels.
And since ABS keeps the braking very near to this level hence ABS cuts braking distance.

Many drivers are able to stop even in shorter distance with non-ABS cars of same specs,weight and tyre width as compared to ABS equipped ones.
What technique they use is:-
They never pump the brakes again and again,instead they develop a habit of pressing the pedal quite slowly in one go and as soon as the braking force increases their pressure on the pedal keeps decreasing and at last comes a position where the brakes are applied at just the verge of locking.If the wheels lock,then they do it again,but its not pumping.This technique needs a lot of practice but once learnt is very usable.My chauffy taught this to me,although I am still not perfect and end up locking the wheels or non-ABS cars.

4. As a Driver, what all things, I should know before i drive a ABS fitted Car, OR is there a change in my Driving style needed before I drive a ABS fitted car.
No need to change driving style,instead now you will have to be more careful while driving non-ABS equipped cars.

I hope I am clear..
 
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So some one told me the other day that you need to practice to drive a vehicle equipped with ABS. (Earlier we had DZire VDi and now Fluidic Verna CRDi)
So was bit confused after that. I knew earlier that how abs works and all but was still in a doubt. But after searching I ended up in this thread. Well I have cleared my doubt and the Video in the first page in very informative![clap]
 
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To make the thread more interesting, I have something for you guys. Kindly watch and comment. I also agree to the idea to some extent. Isn't it similar to the manual and auto transmission case? AT has given us ease to drive in heavy traffic and various other situations, but dont you think they have taken the control from us. Now, we cant change gear at our wish, but depend on "computer ji" to lock to a suitable gear [:)]
Coming back to topic lets watch the video
ABS vs. No ABS - YouTube
 
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^^This video is also somewhat true.It also has the same thing as I have mentioned above.Some drivers know this technique of stopping their cars without ABS too in a distance shorter than ABS equipped cars.
BUT BUT BUT..in case of panic braking,all the techniques are left as it is and only ABS comes handy.
 
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Most important thing to keep in mind:
If you must brake taking full advantage of ABS, slam your ABS brakes and keep it floored. Never pump ABS brakes.
 
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I m not sure to agree or disagree with ABS. Its at the end is a tech and can fail anytime. Rather than believing on this and hope we avoid any dangers. there are few rules i follow may be can be used as a good practice.
1. Always know your vehicle behavior. Until u know your machine never do experiments.
2. Always drive at a controllable speed. Never lose your temper while on wheel.
3. Remember there is some one waiting at home and wanting you to get back.
4. never get intimidated by the next driver. 10 mints late will not get you 100 cores or a gold medal.
This might sound free gyan but try it out and you will see there is no use of ABS. It works for me every day.
 
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Hi Krish,
Very nice post of yours because I see lot of people and friends driving like they will loose 100 crores money or they have to sign a cheque.
I only disagree with the no use of ABS.Its life saver(ABS&Airbags) if we know how to make use of it. I too used to have the same type of feeling about ABS until I had training how to use it.

Simple technique in ABS braking to slam the brakes hard and holding the steering for minimal movement.The engine braking power can also be used.The car stopping distance does not increase because of ABS.
For cars without ABS we should learn to pump the brake pedal 2 to 3 times and make maximum use of the engine braking(only in panic situations,not good for engine).
Not sure for the petrol engines as I drive only diesel powered cars.
 
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Hi Krish,
Very nice post of yours because I see lot of people and friends driving like they will loose 100 crores money or they have to sign a cheque.
I only disagree with the no use of ABS.Its life saver(ABS&Airbags) if we know how to make use of it. I too used to have the same type of feeling about ABS until I had training how to use it.

Simple technique in ABS braking to slam the brakes hard and holding the steering for minimal movement.The engine braking power can also be used.The car stopping distance does not increase because of ABS.
For cars without ABS we should learn to pump the brake pedal 2 to 3 times and make maximum use of the engine braking(only in panic situations,not good for engine).
Not sure for the petrol engines as I drive only diesel powered cars.
 
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Remember, the average Joe on the road does not remember to pump breakes just when needed. We need consistency on the road. You cannot rely on everybody pumping brakes on a non-ABS car. I would rather have all cars with ABS (like many countries) as opposed to having some cars with ABS. The overall road safety is compromised. This is just the other side of the coin that we need to keep in mind.
 
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Yes in panic situations its very difficult to remember tips or anything else.It better to be safe than sorry.I think government should take the initiative of making the manufactures provide ABS & Airbags as mandatory for every car produced.
I suggest all my friends to go for the top end model as it has airbags and ABS.
 
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I personally believe, ABS should be made mandate for all taxi/ Long journey (All India/intern state permit) vehicles. This is very useful in Long drives a
I have never heard/seen an ABS saved an accident or life while driving in City (off course this exclude ring roads and express roads)
Panic situation is very common in city thanx to our road sense but will ABS help?

I am not saying its bad techn. But my point is a proper rd sense will be the right approach rather than belief in ABS.
 

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