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Old 13th January 2010, 14:32   #16
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Originally Posted by RajaTaurus View Post
It brings down the speed to some extent before the ABS kicks in, reducing the risk of overshooting your stopping distance. ABS acts only if you stomp on the pedal suddenly.
Experts can correct me if I am wrong. My understanding of ABS is that stomping the brake and holding it down should give the most effecient stopping. The ABS basically compares the RPM of all wheels and releases and re-engages the brake (in fractions of a second) on the other wheel/s in case one or some of the wheels are skidding (skidding of a particular wheel results in a lower RPM on that wheel). Therefore if the ABS is working well , by pumping and releasing the brakes manually , you would actually end up applying the brakes for a shorter period of time and thereby increasing the stopping distance.
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Old 13th January 2010, 14:38   #17
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Originally Posted by vj_carLover View Post
Ph03n!x - Can you elobarate please further on that. More on the bit of DRIVE part. Would be helpfule for newbies like me.

Cheers
Umm.. what will you do if you find a hen or a dog or whatever crossing the road on your highway travel? Mostly apply the brakes (but not really slamming / trying to stop) while you cut left/ right and then straighten - you are able to do that because the wheels do not get locked (assuming non-ABS car here) - not much of a braking effort to lock the wheels.

In an ABS car, when you are having to slam the brakes, instead of holding on tight to the steering in a straight line or holding it in a constant turning (not really advisable in non-ABS when slamming the brakes unless you know what you are doing) position like we probably do in case of a non-ABS car) to avoid hitting the obstacle, try to drive past it - turn (not a sharp cut, gradual enough turn) a bit right or left even when you brake with all might - and straighten out when you have the space - something you wont even attempt to do in a non-ABS car (where you will come to a full halt before swearing at whatever it is that made you slam the brake, and then go on you way!)

This of course if not possible at all times - there has to be an opportunity to do that. Not sure if am explaining right, it just comes when you are in that tight spot...

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Originally Posted by RajaTaurus View Post
It brings down the speed to some extent before the ABS kicks in, reducing the risk of overshooting your stopping distance. this is normally used in cars without ABS. However, we can reduce the speed by slight slow pumping and then step on the pedal for the ABS to take over.
You may end up prolonging the stopping distance if you pump the brakes in an ABS car instead of just standing on it with all might. The tolerance of the ABS system to wheel locking, and its action of releasing the brakes several is much more effective and sensitive than any humans pumping action.

This is akin to an aeroplane's flight envelope protection, where the extreme actions of the pilot will only be in effect as long as it does not cause adverse reactions on the aircraft (stall / roll etc). I remember reading about this in wiki a while back - a search should tell you what I am intending...

Last edited by ph03n!x : 13th January 2010 at 14:46.
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Old 13th January 2010, 14:59   #18
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Consistent pressure on the brake pedal is very important, People new to Abs equipped cars may let go the brakes pedal when it kicks back when any skidding is detected. I would advise everyone not used to ABS is to practise on a empty stretch preferably with loose gravel (At slower speeds).
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Old 13th January 2010, 15:02   #19
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^^^ Note that ABS on lose gravel condition will actually increase stopping distance - a non-ABS car with wheels locked will stop within a shorter distance on lose gravel, though you wont be able to steer.
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Old 13th January 2010, 15:52   #20
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As owner of an ABS equipped car, lets clear this once and for all. If you have an ABS equipped car, please please dont hesitate to stand on the brakes in an emergency. There is no need to pump, or release pressure in any way.

The thudding sensation that you get is the ABS system automatically pumping the brakes to prevent lockup, and ensuring optimum braking. If you take your foot pressure off, the ABS system gets confused. Don't bother.
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Old 13th January 2010, 16:02   #21
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Quote:
Originally Posted by Shan2nu View Post
Stopping distance is also affected by the condition of the brakes and the tyres.
+1 to that. Trusting ABS to save you from all situations is just being over confident. With proper brakes and tyres one can avoid activating ABS in the first place.

Another thing that goes hand in hand with ABS is EBD. EBD maximizes the brake effectiveness while ABS prevent locking.
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Old 13th January 2010, 19:23   #22
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Its fine to stand on the brakes in an ABS equipped car but making it a habit may not be the best idea. What if you have to drive a non-ABS car someday for some reason? Until India has laws like in Europe where every car has ABS, its not wise to make it a habit. The flipside is an increased probability of actually crashing in your own car because of not standing on the brakes. Its a difficult one, to say the least.

Last edited by McLaren Rulez : 13th January 2010 at 19:30.
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Old 13th January 2010, 19:41   #23
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Originally Posted by Shan2nu View Post
You just need to practice. Take your car out on a lonely stretch, take it to about 100kmph and slam the brakes. The more you do it, the more your brain gets used to it and follows the same intructions in case of a panic situation.

Shan2nu
Just puts you into a dangerous habit if you ever drive a non-ABS car for some reason.
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Old 13th January 2010, 19:59   #24
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Originally Posted by McLaren Rulez View Post
Its fine to stand on the brakes in an ABS equipped car but making it a habit may not be the best idea. What if you have to drive a non-ABS car someday for some reason?
No offence meant, but are we taking the driver's brain totally out of the equation? My other car is a Tata Indica. I also drive dad's company car, Ambassador, occasionaly. None of these have ABS. Many instances where I've had to brake hard in both, and pumping the brakes is the only solution.

Please realize that the driver must be the foremost authority in deciding what strategy to adapt, depending on what his car comes equipped with. The title of this thread is "learning to brake on a car with ABS", and I'm only handing out the right technique.
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Old 13th January 2010, 20:08   #25
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[IMG]file:///C:/DOCUME%7E1/naga/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]
Quote:

Threshold braking (ABS and non-ABS cars)

Threshold braking is the best strategy to adopt to gain maximum braking performance on tarmac. The point of maximum braking performance is found before the point of wheel lock, and when using threshold braking the driver attempts to try and keep the braking pressure just before this point. Practically, it's often very difficult to know exactly the point at which wheels will lock as many factors are at play such as tarmac conditions, tyre choice and brake temperature.
Source- Braking techniques
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Old 13th January 2010, 20:28   #26
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Quote:
Originally Posted by predatorwheelz View Post
No offence meant, but are we taking the driver's brain totally out of the equation? My other car is a Tata Indica. I also drive dad's company car, Ambassador, occasionaly. None of these have ABS. Many instances where I've had to brake hard in both, and pumping the brakes is the only solution.

Please realize that the driver must be the foremost authority in deciding what strategy to adapt, depending on what his car comes equipped with. The title of this thread is "learning to brake on a car with ABS", and I'm only handing out the right technique.
You may want to read the first post again. The OP says this
Quote:
Inspite of knowing that I could apply the brakes all the way on an ABS equipped car, instinct took over and I applied less than possible maximum braking
Its not about brains. Your instincts cannot alter when you drive a different car. Its obvious that maximum braking is the best way to stop an ABS equipped car in an emergency but whether one should try learning it and making it the instinctive reaction is the question.

I've no idea how you manage to brake one way in the non ABS car and another way in ABS equipped cars in panic situations. I can only conclude that those hard brakings were not quite panic stops.
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Old 13th January 2010, 20:28   #27
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Here is a different take on ABS:
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Old 18th January 2010, 03:13   #28
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Originally Posted by adnaps View Post
This morning I had a situation where I had to stop suddenly from a speed of 120 Kmph. Inspite of knowing that I could apply the brakes all the way on an ABS equipped car, instinct took over and I applied less than possible maximum braking.....
To me, this might point to the fact that it wasn't a truly reflex / emergency braking. The kind where your heart jumps into your throat.

The fact that you didn't have a collision might mean that you had a split second to evaluate the situation, and chose to go easy on the pedal.

Do you think this is possible?

Let me rephrase that :

If the obstacle was 10 feet closer, do you think you would have pressed that pedal harder ?



Quote:
Originally Posted by ph03n!x View Post
....@ssbiitm - you are right about braking distance is never less with ABS...
Actually this is incorrect.

AFAIK Shan2nu was right when he said that on dry tarmac ABS can provide better stopping distances.

There is ofcourse debate on this point (ie non-ABS threshold braking may be superior), but i think the fact is that if you take 100 random drivers and get them all to stop as short as they can in an ABS car and a Non-ABS car, the ABS car will be the winner.

Quote:
Originally Posted by RajaTaurus View Post
....At high speeds, whenever possible, it is better to pump the brake a bit before you really HAVE to stand on it.
I disagree with this. Partly because of the definition of "pump".

See, as someone has already mentioned, the max braking efficiency is at the point just before the tyres lock up.

ABS plays around by "pumping" (bad word - i prefer pulsing) the brakes every time the tyres lock up. Several times a second.

In effect, this borders around that area of max efficiency.

On a non-ABS car, there is NO WAY you can get the same effect by pumping the brakes.

What you should concentrate on is threshold braking -- trying to apply as much pressure as possible on the brakes, without letting your tyres lock up.

IF you think your tyres have locked up, release the pedal slightly (not totally) and then reapply some pressure. (ie ONE pump)

Don't constantly pump the brakes, and by no means "pump" the brakes by releasing them totally every time.
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Old 18th January 2010, 03:21   #29
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Infact pumping the brakes too much can upset the weight transfer of the car and create further complications.

The smoother you are with your braking, the easier it is to keep control over the car.

Shan2nu
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Old 18th January 2010, 03:51   #30
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Quote:
Originally Posted by ph03n!x View Post
.... in ABS cars, you gotta DRIVE even while you are braking hard!!
Absolutely. Though a few things to keep in mind :

1) Will you be doing MORE damage by steering?
- Hitting a tree can be much worse than hitting the car in front of you
- Are there pedestrians whose lives you might be endangering?
- Are there bikers in the lanes besides you?

These are things you have to be VERY careful about. Sometimes you might steer to avoid a collision which would have eventually been at 20km/h costing you only a new bumper -- but might instead suddenly cut infront of a biker, causing much more damage.

Weigh the situation before acting.


2) Don't focus on the object you are going to collide with -- focus on the gaps around it.


Quote:
Originally Posted by McLaren Rulez View Post
Its fine to stand on the brakes in an ABS equipped car but making it a habit may not be the best idea. What if you have to drive a non-ABS car someday for some reason? Until India has laws like in Europe where every car has ABS, its not wise to make it a habit. The flipside is an increased probability of actually crashing in your own car because of not standing on the brakes. Its a difficult one, to say the least.
Sudden braking = Threshold braking (in ABS and Non-ABS)

EMERGENCY (reflex) braking = ABS (or lockup in Non-ABS)


Quote:
Originally Posted by Shan2nu View Post
.....Stopping distance is also affected by the condition of the brakes and the tyres....
Absolutely agree.
You can save a lot more meters just by getting better tyres and keeping your brakes in good condition.

Also, one more variable is the quality and design of the ABS system itself!! Not all ABS systems are created equal!


And finally, on a closing note, i will say that i have been in a minor accident THANKS TO ABS (in the snow). I'm certain that if the car did NOT have ABS it would have been avoided!

cya
R
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