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Old 1st December 2008, 05:15   #211
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Originally Posted by sukrit7 View Post
Claims. I did get the idea to pump it when it started skidding but my mind just didn't allow me to take my foot off the brake.
I've been wondering. When we panic brake in a non abs vehicle, what exactly happens? do only the rear wheels go into a skid or do all four. Please let me know. Am curious.
Depends on how many wheels lock. All four/three/two/one. Which depends on what surface each wheel is on(for eq:- it can happen that one wheel is on mud/gravel/ice, while all the other three on dry tarmac or vice versa). When all the wheels lock, the car just hurtles in the general direction where it was pointed before the skid started, and does not respond to steering input. When the rear wheels alone lock, and you have the front wheels not pointed straight, expect to face the direction in which you came from. Front wheels alone locking leads to understeer, I guess. Other combinations of wheel locks, I do not know what happens, but I presume are less dangerous.

ABS with wheel speed sensors for each wheel, are able to decide which wheel is getting locked and distributes braking force accordingly(EBD).
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Old 1st December 2008, 18:13   #212
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Thanku. that explains a lot
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Old 24th July 2010, 17:02   #213
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Using an old thread on ABS.

Folks, I don't know if this has been proposed in any other thread (mods please delete if already suggested elsewhere). Is it possible to take information of these safety features away from the forum into the larger world? Can we as team-bhp come out with a half-page ad in major newspapers explaining what ABS is, whats its not, and how the world over it is considered a standard fitting on vehicles? This should be in layman terms - I think this thread has all this information. Maybe that could nudge manufacturers into making ABS standard across vehicles?

Maybe SIAM, ARAI or other such bodies could sponsor these ads? Or member contributions can easily help in paying for these ads.
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Old 28th July 2010, 17:17   #214
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Independent brakking for the wheels.While turning this will play their role very effieciently.

Eitherwise turning(Right or left) the rotaion of the wheels will differ.At that time when you put brake,Ordinary type will work as same for allthe wheels.ABS here will work as per the wheel rotation.So the tyres will stop equally.

But anyway this all will only work if the tyres are all of same condition.If any one or two is different in the grip (highly used),this will not help.Wheel will get stopped,but the vehicle will never stop.

If grip is not there for one wheel,the skidding will be there unevenly.So all the tyres need to be checked and while changing change all the wheels will only help with ABS efficiently.
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Old 13th August 2010, 09:38   #215
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Sorry guys for breaking in, but let us settle the dust on ABS.
Remember, I am talking out of my hat (I am no authority on this), and you could correct me if you please.

What is ABS?
Simply, Antilock Braking System.
Brake pads apply friction on brake-drum hence on wheel.
Too much pressure on brake-pads (hard braking) can cause wheel-locking. Locking means no relative motion between pads and wheel = wheels not rotating.

Why is locking bad?
As a kid I had felt locking was good for the following simple reason:
If I am trying to stop the wheel from rotating then locking is the ultimate victory for me. But locking, it seems, is not good for two reasons.
One: Steering control is lost when wheels are locked.
Two: Braking efficiency is reduced when wheels are locked.

One: When wheels are rotating the car steers in the direction of wheels. When wheels are locked the car becomes a sled and its direction of travel is not determined by the direction of wheels. In short, the car's motion goes out of control.

Two: When wheels are locked, the friction against motion of car goes between the wheels and the ground. When wheels are not locked, the friction is established between the brake-pads and the brake-drum. This friction is obviously greater than the former type. Disk brakes are said to be superior to drum brakes in producing this friction.

ABS action: Apply maximum possible friction between brake-pads and brake-drum without locking the wheel. ABS therefore stops the car in the shortest distance and keeps the car steerable even during hard braking.

If your car does not have ABS then the safety factoring would consist of limiting the speed of the car and ensuring that tyres are not over-inflated.
That is your carma!

Correctly inflated tyres make a rectangular imprint on the ground. Over-inflated tyres make an oval imprint on the ground and provide less friction. Mud, water, slurry, loose gravel, and such other things drastically reduce friction between the wheels and ground. Skidding occurs when wheels are slipping rather than rotating on the ground. Brake-pad friction is always greater than skid friction, by design.

Happy and safe driving to all; and beg your pardon for being so basic.
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Old 13th August 2010, 15:43   #216
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My basic problems with drivers and ABS.

The right thing to do with ABS: Forget that it is there.

Among the many wrong things:
  • Believe that you can drive faster as your brakes are somehow better
  • Believe that you can drive closer to the car in front, because your stopping distance is reduced
  • Believe you can take more risk because your brakes will get you out of trouble
  • Think that it is just fine to brake while cornering, as, hey, ABS!
ABS may save your (or someone else's; maybe a stray pedestrian or cow) skin in an emergency. Ideally, driving does not include emergencies!
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Old 14th August 2010, 00:41   #217
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Default A Different approach on ABS!

Quote:
Originally Posted by Thad E Ginathom View Post

Among the many wrong things:
  • Believe that you can drive faster as your brakes are somehow better
  • Believe that you can drive closer to the car in front, because your stopping distance is reduced
  • Believe you can take more risk because your brakes will get you out of trouble
  • Think that it is just fine to brake while cornering, as, hey, ABS!
Very well said!.

Check this video, it gives us a very different perspective of ABS. ABS is safe under certain conditions, but then it depends. The safety of ABS is extremely conditional, and this video, and the related episodes will demonstrate how.



P.S - I'm not sure of this has been posted before, if so pardon me.
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Old 14th August 2010, 01:25   #218
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well, on a loose gritty or sandy surface, or on ice, ABS is useless, which is one of the reasons we should not rely on it in the sense of letting it change our driving style. I don't argue that it is not good overall, though: I'd rather have a car with, than without it.

Just that it should be thought of as an emergency system: never as an every-day system.
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Old 18th August 2010, 17:00   #219
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Quote:
Originally Posted by Thad E Ginathom View Post
well, on a loose gritty or sandy surface, or on ice, ABS is useless.
respectfully I'd strongly disagree on the above statement.
Even though in the above said conditions a vehicle equiped with ABS (anti blockier system) would have a longer stopping distance than one without ABS, the former still would have better vehicle control.

Vehcile control is equally if not less important that braking distance. Given an option I would like to miss colliding with an object by maneuvering the car out of its way rather than come to a screeching halt just inches before impending doom...have had a couple of situations where ABS saved me not because of its stopping power but due to vehicle control.

peace,
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Old 18th August 2010, 17:26   #220
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It would be nice to know, would you mind elaborating on those incidents?
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Old 18th August 2010, 17:58   #221
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Originally Posted by santosh.s View Post
It would be nice to know, would you mind elaborating on those incidents?
did not want to re-live those in my mind but here goes

Chennai-Sriperumbedur road (2006 or 07) - was testing some ABS systems at a testing facility. On low fricition surfaces the stopping distance is abnormally large when compared to a dry surface and one may not realize this until one actually comes across such a situation (hope no one actually does so)
Did not realize this fact untill it was a bit late and dispite my full braking effort the car was not about to stop as aspected..was just able to maneuver the car to miss a potentially deadly collision and escape with a minor scratch on the car
Dallas (Aug 2008) - raining cats and dogs (quite unlike Dallas weather) and me happily returning from work in my Mazda 626. My car did not have ABS but am glad that the Ford F-150 did. Had to stop at a traffic signal but could not as my car hit a puddle n kept on going only to stop in the middle of the intersection. Just my luck that the driver driver that was to hit me on the side was able to brake and maneuver to stop besides me..am pretty sure he too would have kept on going straight if he would not have had an ABS system in his truck.

peace,
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Old 18th August 2010, 18:20   #222
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Quote:
Originally Posted by kapilvgupta View Post
respectfully I'd strongly disagree on the above statement. ... Vehcile control is equally if not less important that braking distance.
Hence my statement. On light gravel or ice, the tyres have little or no grip even with ABS, so there is also little or no steering.

Ice is the ultimate: I've done this experiment. I did it at very, very slow speed, as I was worried about the car sliding sideways*. Brake sharply, on ice, and the ABS operates, but the car is still sliding.




*Anyway, driving on ice at any other speed is a little crazy!
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Old 18th August 2010, 22:34   #223
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Quote:
Originally Posted by kapilvgupta View Post
did not want to re-live those in my mind but here goes

Chennai-Sriperumbedur road (2006 or 07) - was testing some ABS systems at a testing facility. On low fricition surfaces the stopping distance is abnormally large when compared to a dry surface and one may not realize this until one actually comes across such a situation (hope no one actually does so)
Did not realize this fact untill it was a bit late and dispite my full braking effort the car was not about to stop as aspected..was just able to maneuver the car to miss a potentially deadly collision and escape with a minor scratch on the car
no offense but your testing facility needs to work on it's procedures. It would have been an embarrassment to have a deadly collision in a facility testing ABS equipment .
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Old 19th August 2010, 09:45   #224
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I would like to see a comment from someone whom I know & can trust,
Hmmm GTO has had the pleasure of driving the Civic(ABS) & City(OHC non ABS) and he is a very good driver I believe, his comments would be appreciated here
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Old 19th August 2010, 23:21   #225
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Quote:
Originally Posted by gostel View Post
ABS action: Apply maximum possible friction between brake-pads and brake-drum without locking the wheel. ABS therefore stops the car in the shortest distance and keeps the car steerable even during hard braking.
Little bit of correction. ABS does not apply maximum friction. But its a ecu controlled unit that contracts and retracts the pads in very fast succession, hence preventing it from getting heated (main cause of wheel lockup) all of a sudden and avoiding locking.

Quote:
If your car does not have ABS then the safety factoring would consist of limiting the speed of the car and ensuring that tyres are not over-inflated.
my 38 years old 4x4 does not have ABS at all, and used in extreme slopes. We normally simulate ABS like system by pressing and releasing brake pedal in succession, hence preventing lock up.

ABS is a good thing when used with technical zingo called EBD. This is quite effective in Safari that i tested long ago. What they say it does is it distributes braking power evenly. When its need? on curves, where different wheels are at different RPM.

What is Bad thing about ABS? you cannot do weird fancy stuff if you have car with ABS . Not that i am recommending it to do it as a responsible member of tbhp.

Last edited by SirAlec : 19th August 2010 at 23:25.
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