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Unchained
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Hi humans being, I have an inquiring question regarding brakes, more specifically, anti-lock brakes. When driving my '85 Celica I'll usually pump the brakes slightly when approaching a stop. The brakes are in no way soft or mushy, but pumping them 2 or 3 times seems to provide better stopping pressure than if they're simply jammed all in one big shot. Besides that, applying the brakes for a few strong compressions results in less brake wear than if they are applied slowly for a greater distance.

Now, a few years ago, before I had my '93 Supra, I remember hearing someone say that pumping the brakes of an anti-lock brake equiped car was not good for the system. Is this true? If so, what are the problems that this could cause if any? Just wondering.


A fine is a tax for doing wrong. A tax is a fine for doing well.
Scott
 

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Marblehead said:
Now, a few years ago, before I had my '93 Supra, I remember hearing someone say that pumping the brakes of an anti-lock brake equiped car was not good for the system. Is this true? If so, what are the problems that this could cause if any? Just wondering.

Scott
The fastest way of stoping a car with anti-lock brakes is pressing the brakes as hard as possible. This allows the ABS to modulate the breaks and keep the tires right at the edge of maximum traction. So you get maximum stoping power and maintain stearing control.

If you don't have ABS pumping the brakes will keep the wheels from locking up and allow to to keep stearing (to avoid an accident). But unless you are really good, pumping non-ABS will not give you as short a stoping distance as ABS.

If you are not employing the brakes at (or near) their limit, then ABS/pumping wont have much any effect at all.
 

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"pumping" the brakes on an ABS car will not hurt anything, it just won't stop as fast.
the ABS "pumps" the brakes to a skid limit then lets off (all faster than a human could do).
Just get in a MKIV with decent stock brakes, get up to say 100, then slam on the brakes. You will not believe how quick it stops.
 

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VickSupra said:
"pumping" the brakes on an ABS car will not hurt anything, it just won't stop as fast.
the ABS "pumps" the brakes to a skid limit then lets off (all faster than a human could do).
Just get in a MKIV with decent stock brakes, get up to say 100, then slam on the brakes. You will not believe how quick it stops.
And just for more fun, turn the wheel while you are stopping and see how you still have control.
 

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Unchained
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Discussion Starter #5
Mary-Kate Olsen said:


And just for more fun, turn the wheel while you are stopping and see how you still have control.

Yeah, a few critters lives have been spared by the ABS of the Supra....all except for that poor bird who hit the mirror...sorry lil' fella. Regarding your previous response about hitting the brakes hard. It's funny to see the expression on the faces of the cross traffic when they see you screaming up to intersection, they have the green light and thinking you're not going to stop. Obviously they don't realize the power of the Supra and it's brakes.

Thanks for the replies.

Nothing is fool proof to a sufficiently talented fool.
Scott
 
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Actally, ABS brakes ONLY allows the driver to still have control over the car when braking "fully" (driver is still able to steer the car). The ABS system does NOT stop the car easier and does NOT shorten the length of the brake...
 

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Goldensupra said:
Actally, ABS brakes ONLY allows the driver to still have control over the car when braking "fully" (driver is still able to steer the car). The ABS system does NOT stop the car easier and does NOT shorten the length of the brake...
Yous statment is only true when compairing a very skilled driver to ABS. As I am sure you know there are two basic types of friction between surfaces. Static friction (when the two surfaces are not moving relitive to eachother) and kinetic friction (when the srufaces are sliding aginst eachother).

The static friction is always higher then the kinetic friction. This is why when you are trying to push a large box across the floor it's real hard to get it started, but once it starts to move you don't have to push as hard to keep it going.

The same is true with tires contacting the road. normaly a tire's contact patch doesn't move in relation to the road surface so you get the higher static friction to move the car. But if you slip the tires (burnout, drift, lock the breaks) the tire's contact patch moves across the road and now you are only getting the kinetic friction to help control the car.

Well that turned out longer then I expected. So I'll end the science lesson here. The morral of the story is: locking the breaks is bad.
 

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Goldensupra said:
Actally, ABS brakes ONLY allows the driver to still have control over the car when braking "fully" (driver is still able to steer the car). The ABS system does NOT stop the car easier and does NOT shorten the length of the brake...
It IS easier to come to a safe stop with ABS. NO driver can pump with the speed and accuracy of the ABS.
The whole point is to keep max traction without sliding (that's what MKO is saying in 1500 words or less)!
 
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