Why do some people say ABS *DOESN'T* shorten the braking distance?

[Zenmervolt]

Originally posted by: ndee

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: PlatinumGold

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

abs is grabbing and releasing grabbing and releasing. if you look at the treadmark of a car stopped using abs on dry you will see dash blank dash blank where the abs is activated.

brakes without abs would leave a solid skid mark.

yes, I know that they dash-blank-dash-blank. But don't the brakes absorb more energy when they're not sliding?

ABS releases the brakes _completely_ when it pulses. So those "blank" areas are when the car has _zero_ braking force.

ZV

oh, not only releasing it a little bit, so far that you stop slidding? That's what I thought would ABS work.

No, it doesn't release "just a little" because once the tire has locked up, it needs to spin up to speed again, and this happens fastest with the brake released completely. In essence, the wheel has to regain tractive force after locking up and the best way for that to happen is for the brake to be released completely.

ZV

 

[ndee]

Originally posted by: DougK62

Originally posted by: ndee

Originally posted by: DougK62

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

Why WOULDN'T it increase stopping distances? ABS is just a computer pumping the brakes - just as a person with a non-ABS car would pump the brakes manually. Do you really think that letting OFF of the brakes is going to give you a shorter stopping distance than if you just stay on them? It just doesn't make sense.

if you slide, breaking distance increases.

Well I'm just going to give you a big "DUH" on that one. Where did I say anything about sliding?

I didn't know it was fully releasing the breaks. If I compare ABS vs non-ABS, I always compare sliding vs ABS-style breaking.

 

[rh71]

Did you really need to start a new thread on this ?

Check howstuffworks. They are the authority just like God is.

 

[ZeroNine8]

Originally posted by: ndee

Originally posted by: ZeroNine8
Actually you can stop a car faster if you don't lock up the brakes because tires, like most things, have higher static friction than kinetic friction. By keeping the tires just on the verge of breaking loose from pavement you will have greater stopping force than just locking them up. ABS works better than non ABS for the average driver, however it is possible to stop faster without ABS for skilled drivers who know how to keep the tires closer to that break point. The other big thing, as was already said, locked up tires don't allow any real steering, so you essentially have no control while skidding.

but couldn't ABS be made that one thousands of a second before the tires start to slide, they release the break a little bit?

It can try, but you can't predict the future. Since all kinds of different road conditions, tire conditions, weather, etc. affect the stopping force that can be applied, the engineers must account for the worst case scenario that will be covered by ABS. Since no ABS systems can adjust to all of these factors, there will be situations where the brake releases well before the car would slide, since the stopping force has exceeded the designed maximum. If traction conditions never changed, ABS could be tweaked to stop much better than it does, however it is designed to perform better in most situations for the average driver.

 

[ndee]

Originally posted by: rh71
Did you really need to start a new thread on this ?

Check howstuffworks. They are the authority just like God is.

I will next time

 

[PlatinumGold]

Originally posted by: DougK62

Originally posted by: ndee

Originally posted by: DougK62

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

Why WOULDN'T it increase stopping distances? ABS is just a computer pumping the brakes - just as a person with a non-ABS car would pump the brakes manually. Do you really think that letting OFF of the brakes is going to give you a shorter stopping distance than if you just stay on them? It just doesn't make sense.

if you slide, breaking distance increases.

Well I'm just going to give you a big "DUH" on that one. Where did I say anything about sliding?

again, look at the skid marks from an abs vehicle, all the dashes of skidmarks are guess what, sliding. so yes, you do slide with abs.

abs is helpful in bad road conditions, in good road conditions a good driver with a good feel will never engage the abs and will stop faster because they will never induce a skid.

 

[spidey07]

wow. Just...wow.

 

[Zenmervolt]

Originally posted by: ndee

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: ZeroNine8
Actually you can stop a car faster if you don't lock up the brakes because tires, like most things, have higher static friction than kinetic friction. By keeping the tires just on the verge of breaking loose from pavement you will have greater stopping force than just locking them up. ABS works better than non ABS for the average driver, however it is possible to stop faster without ABS for skilled drivers who know how to keep the tires closer to that break point. The other big thing, as was already said, locked up tires don't allow any real steering, so you essentially have no control while skidding.

but couldn't ABS be made that one thousands of a second before the tires start to slide, they release the break a little bit?

Not without somehow knowing the exact amount of traction available at that instant. That's something that cannot be programmed into the computer or even truly monitored.

ZV

I see, I thought it could

There are so many variable to control the amount of traction available. Surface type (infinite variations since no two surfaces offer exactly the same traction, no two roads and not even the same road at different times), temperature, tire age, tire tread, tire make/model, tire inflation, tire load...

ZV

 

[Siddhartha]

IIRC, ABS keeps you from locking up your brakes.

 

[ndee]

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: ZeroNine8
Actually you can stop a car faster if you don't lock up the brakes because tires, like most things, have higher static friction than kinetic friction. By keeping the tires just on the verge of breaking loose from pavement you will have greater stopping force than just locking them up. ABS works better than non ABS for the average driver, however it is possible to stop faster without ABS for skilled drivers who know how to keep the tires closer to that break point. The other big thing, as was already said, locked up tires don't allow any real steering, so you essentially have no control while skidding.

but couldn't ABS be made that one thousands of a second before the tires start to slide, they release the break a little bit?

Not without somehow knowing the exact amount of traction available at that instant. That's something that cannot be programmed into the computer or even truly monitored.

ZV

I see, I thought it could

There are so many variable to control the amount of traction available. Surface type (infinite variations since no two surfaces offer exactly the same traction, no two roads and not even the same road at different times), temperature, tire age, tire tread, tire make/model, tire inflation, tire load...

ZV

so actually the tire should be full of sensors to meassure "sliding" eh?

 

[DougK62]

Originally posted by: ndee

Originally posted by: DougK62

Originally posted by: ndee

Originally posted by: DougK62

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

Why WOULDN'T it increase stopping distances? ABS is just a computer pumping the brakes - just as a person with a non-ABS car would pump the brakes manually. Do you really think that letting OFF of the brakes is going to give you a shorter stopping distance than if you just stay on them? It just doesn't make sense.

if you slide, breaking distance increases.

Well I'm just going to give you a big "DUH" on that one. Where did I say anything about sliding?

I didn't know it was fully releasing the breaks. If I compare ABS vs non-ABS, I always compare sliding vs ABS-style breaking.

Then you're doing a horrible comparison. Non-ABS braking isn't sliding. Like others have said, you get the best non-ABS braking at the limit of adhesion - that's not sliding.

 

[LAUST]

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: ZeroNine8
Actually you can stop a car faster if you don't lock up the brakes because tires, like most things, have higher static friction than kinetic friction. By keeping the tires just on the verge of breaking loose from pavement you will have greater stopping force than just locking them up. ABS works better than non ABS for the average driver, however it is possible to stop faster without ABS for skilled drivers who know how to keep the tires closer to that break point. The other big thing, as was already said, locked up tires don't allow any real steering, so you essentially have no control while skidding.

but couldn't ABS be made that one thousands of a second before the tires start to slide, they release the break a little bit?

Not without somehow knowing the exact amount of traction available at that instant. That's something that cannot be programmed into the computer or even truly monitored.

ZV

I see, I thought it could

There are so many variable to control the amount of traction available. Surface type (infinite variations since no two surfaces offer exactly the same traction, no two roads and not even the same road at different times), temperature, tire age, tire tread, tire make/model, tire inflation, tire load...

ZV

:beer::beer: :gift:

Isn't it interesting how almost everything in life gets effected by variables

 

[Spencer278]

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: PlatinumGold

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

abs is grabbing and releasing grabbing and releasing. if you look at the treadmark of a car stopped using abs on dry you will see dash blank dash blank where the abs is activated.

brakes without abs would leave a solid skid mark.

yes, I know that they dash-blank-dash-blank. But don't the brakes absorb more energy when they're not sliding?

ABS releases the brakes _completely_ when it pulses. So those "blank" areas are when the car has _zero_ braking force.

ZV

No during the blank lines you have the most braking force. When the brakes are released your wheel has stopped spinning but moving forward at 30 mph once the wheel stops sliding it will be rolling with the same speed as the car to get the wheel spinning at 30 mph takes energy from the car those slowing it down.

 

[Zenmervolt]

Originally posted by: Spencer278

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: PlatinumGold

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

abs is grabbing and releasing grabbing and releasing. if you look at the treadmark of a car stopped using abs on dry you will see dash blank dash blank where the abs is activated.

brakes without abs would leave a solid skid mark.

yes, I know that they dash-blank-dash-blank. But don't the brakes absorb more energy when they're not sliding?

ABS releases the brakes _completely_ when it pulses. So those "blank" areas are when the car has _zero_ braking force.

ZV

No during the blank lines you have the most braking force. When the brakes are released your wheel has stopped spinning but moving forward at 30 mph once the wheel stops sliding it will be rolling with the same speed as the car to get the wheel spinning at 30 mph takes energy from the car those slowing it down.

OK, you have me on a technicality, but the point that there are periods during the ABS stop where there is zero braking force stands. I suppose that the most accruate thing would be to say that during the initial part of the blank there is no braking force as the tire spins back up to speed and during the latter part of the blank on through the black rubber mark there is maximum braking force causing the tire to lock.

ZV

 

[GTaudiophile]

ABS should have been called Ability to Brake and Steer.

 

[Zenmervolt]

Originally posted by: ndee

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: ZeroNine8
Actually you can stop a car faster if you don't lock up the brakes because tires, like most things, have higher static friction than kinetic friction. By keeping the tires just on the verge of breaking loose from pavement you will have greater stopping force than just locking them up. ABS works better than non ABS for the average driver, however it is possible to stop faster without ABS for skilled drivers who know how to keep the tires closer to that break point. The other big thing, as was already said, locked up tires don't allow any real steering, so you essentially have no control while skidding.

but couldn't ABS be made that one thousands of a second before the tires start to slide, they release the break a little bit?

Not without somehow knowing the exact amount of traction available at that instant. That's something that cannot be programmed into the computer or even truly monitored.

ZV

I see, I thought it could

There are so many variable to control the amount of traction available. Surface type (infinite variations since no two surfaces offer exactly the same traction, no two roads and not even the same road at different times), temperature, tire age, tire tread, tire make/model, tire inflation, tire load...

ZV

so actually the tire should be full of sensors to meassure "sliding" eh?

That's basically what it does, the system measures wheel speed and if one of the wheels stops when the rest are still spinning it lets go of the brakes for that wheel until it starts spinning again.

I suppose that theoretically if every wheel locked fully at exactly the same time then the system might think that the car was stopped and it would allow the brakes to stay locked but I am not sure since there may be some sort of algorhythm that would "notice" that all the wheels had stopped too suddenly. It's a moot point anyway since there is essentially no chance of having all the wheels lock up at precisely the same time.

ZV

 

[LAUST]

To tell you the truth Ndee The best thing to do is go to a snow covered parking lot late at night, and try braking and steering, then pull your ABS fuse and do it some more. There is NOTHING better then getting comfortable with it first hand. No computer is going to just save your azz, and all the info you get from others is a great tool but you still should get some experience in it yourself.

If I ran the Department of Transportation Drivers License Testing each facility would have a skating rink available so they could offer classes and the experience on the ice.

 

[Spencer278]

Originally posted by: Zenmervolt

Originally posted by: Spencer278

Originally posted by: Zenmervolt

Originally posted by: ndee

Originally posted by: PlatinumGold

Originally posted by: ndee

Originally posted by: Zenmervolt
Because it doesn't. It increases stopping distance in favor of keeping control. Fully locked brakes actually stop a car very quickly on dry pavement, but you don't have any control while that is happening which is a very bad thing. ABS very slightly increases stopping distance under _most normally encountered conditions_ in favour of allowing the driver to maintain control. This is a good tradeoff for most people.

ZV

why would it increase stopping distance? Because you don't "slide"?

abs is grabbing and releasing grabbing and releasing. if you look at the treadmark of a car stopped using abs on dry you will see dash blank dash blank where the abs is activated.

brakes without abs would leave a solid skid mark.

yes, I know that they dash-blank-dash-blank. But don't the brakes absorb more energy when they're not sliding?

ABS releases the brakes _completely_ when it pulses. So those "blank" areas are when the car has _zero_ braking force.

ZV

No during the blank lines you have the most braking force. When the brakes are released your wheel has stopped spinning but moving forward at 30 mph once the wheel stops sliding it will be rolling with the same speed as the car to get the wheel spinning at 30 mph takes energy from the car those slowing it down.

OK, you have me on a technicality, but the point that there are periods during the ABS stop where there is zero braking force stands. I suppose that the most accruate thing would be to say that during the initial part of the blank there is no braking force as the tire spins back up to speed and during the latter part of the blank on through the black rubber mark there is maximum braking force causing the tire to lock.

ZV

In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

 

[Zenmervolt]

Originally posted by: Spencer278
In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

You're looking at it wrong. Friction between the tire and the ground is not the same as braking force. You're right that there is least friction between the tire and the ground when the tire is skidding, but there is less _stopping force_ (i.e. force being applied to the mass of the car for the purpose of deceleration) when the brake is released than there is when the brake is fully locked. There is minimal stopping force with a locked wheel. There is _zero_ stopping force when the caliper is released to allow the wheel to start spinning again.

ZV

 

[Spencer278]

Originally posted by: Zenmervolt

Originally posted by: Spencer278
In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

You're looking at it wrong. Friction between the tire and the ground is not the same as braking force. You're right that there is least friction between the tire and the ground when the tire is skidding, but there is less _stopping force_ (i.e. force being applied to the mass of the car for the purpose of deceleration) when the brake is released than there is when the brake is fully locked. There is minimal stopping force with a locked wheel. There is _zero_ stopping force when the caliper is released to allow the wheel to start spinning again.

ZV

Where does the wheel get the energy to spin when the caliper is released? From the moving car assuming your not on the gas at the same time the only way to turn the wheel is from friction on the ground decelerating the car. It takes the same amount of energy to stop a spinning wheel as it does to make a wheel spin.

 

[WinkOsmosis]

Originally posted by: ndee

Originally posted by: ZeroNine8
Actually you can stop a car faster if you don't lock up the brakes because tires, like most things, have higher static friction than kinetic friction. By keeping the tires just on the verge of breaking loose from pavement you will have greater stopping force than just locking them up. ABS works better than non ABS for the average driver, however it is possible to stop faster without ABS for skilled drivers who know how to keep the tires closer to that break point. The other big thing, as was already said, locked up tires don't allow any real steering, so you essentially have no control while skidding.

but couldn't ABS be made that one thousands of a second before the tires start to slide, they release the break a little bit?

Not really. But anyway, the slide-rol-slide-roll stops you faster than slide------------. That is fact.

 

[WinkOsmosis]

Originally posted by: Zenmervolt

Originally posted by: Spencer278
In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

You're looking at it wrong. Friction between the tire and the ground is not the same as braking force. You're right that there is least friction between the tire and the ground when the tire is skidding, but there is less _stopping force_ (i.e. force being applied to the mass of the car for the purpose of deceleration) when the brake is released than there is when the brake is fully locked. There is minimal stopping force with a locked wheel. There is _zero_ stopping force when the caliper is released to allow the wheel to start spinning again.ZV

As far as I know, it doesn't release the brake fully.

 

[Zenmervolt]

Originally posted by: Spencer278

Originally posted by: Zenmervolt

Originally posted by: Spencer278
In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

You're looking at it wrong. Friction between the tire and the ground is not the same as braking force. You're right that there is least friction between the tire and the ground when the tire is skidding, but there is less _stopping force_ (i.e. force being applied to the mass of the car for the purpose of deceleration) when the brake is released than there is when the brake is fully locked. There is minimal stopping force with a locked wheel. There is _zero_ stopping force when the caliper is released to allow the wheel to start spinning again.

ZV

Where does the wheel get the energy to spin when the caliper is released? From the moving car assuming your not on the gas at the same time the only way to turn the wheel is from friction on the ground decelerating the car. It takes the same amount of energy to stop a spinning wheel as it does to make a wheel spin.

I swear, it's like taking to a wall.

We aren't talking about the individual wheel. We're talking about the force imparted on the overall car. Two different things. One is rotational, the other is linear. The same amount of force is applied to the wheel, yes, but the same amount of force _is not_ applied to the _car_.

According to your claim, if I locked all four tires and immediately took my foot off the brake and coasted for the remainder of the stop I would stop in the same amount of time as if the brakes stayed locked. Not true.

ZV

 

[Spencer278]

Originally posted by: Zenmervolt

Originally posted by: Spencer278

Originally posted by: Zenmervolt

Originally posted by: Spencer278
In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

You're looking at it wrong. Friction between the tire and the ground is not the same as braking force. You're right that there is least friction between the tire and the ground when the tire is skidding, but there is less _stopping force_ (i.e. force being applied to the mass of the car for the purpose of deceleration) when the brake is released than there is when the brake is fully locked. There is minimal stopping force with a locked wheel. There is _zero_ stopping force when the caliper is released to allow the wheel to start spinning again.


ZV

Where does the wheel get the energy to spin when the caliper is released? From the moving car assuming your not on the gas at the same time the only way to turn the wheel is from friction on the ground decelerating the car. It takes the same amount of energy to stop a spinning wheel as it does to make a wheel spin.

I swear, it's like taking to a wall.

We aren't talking about the individual wheel. We're talking about the force imparted on the overall car. Two different things. One is rotational, the other is linear. The same amount of force is applied to the wheel, yes, but the same amount of force _is not_ applied to the _car_.

According to your claim, if I locked all four tires and immediately took my foot off the brake and coasted for the remainder of the stop I would stop in the same amount of time as if the brakes stayed locked. Not true.

ZV

Where does the energy come from to turn the locked up wheel. Or are you saying it never starts turning again. Only two things are in contact with the wheel the road and the car and I have yet to see a road that turns my wheels for me.

 

[WinkOsmosis]

Originally posted by: Spencer278

Originally posted by: Zenmervolt

Originally posted by: Spencer278

Originally posted by: Zenmervolt

Originally posted by: Spencer278
In the simple ABS with the slame on the brakes release method in theory there should never be a time with less friction then when the car is skidding ie the black patch. The problem comes from not detecting when the wheel first start to spin and when the wheel first start to stop.

You're looking at it wrong. Friction between the tire and the ground is not the same as braking force. You're right that there is least friction between the tire and the ground when the tire is skidding, but there is less _stopping force_ (i.e. force being applied to the mass of the car for the purpose of deceleration) when the brake is released than there is when the brake is fully locked. There is minimal stopping force with a locked wheel. There is _zero_ stopping force when the caliper is released to allow the wheel to start spinning again.


ZV

Where does the wheel get the energy to spin when the caliper is released? From the moving car assuming your not on the gas at the same time the only way to turn the wheel is from friction on the ground decelerating the car. It takes the same amount of energy to stop a spinning wheel as it does to make a wheel spin.

I swear, it's like taking to a wall.

We aren't talking about the individual wheel. We're talking about the force imparted on the overall car. Two different things. One is rotational, the other is linear. The same amount of force is applied to the wheel, yes, but the same amount of force _is not_ applied to the _car_.

According to your claim, if I locked all four tires and immediately took my foot off the brake and coasted for the remainder of the stop I would stop in the same amount of time as if the brakes stayed locked. Not true.

ZV

Where does the energy come from to turn the locked up wheel. Or are you saying it never starts turning again. Only two things are in contact with the wheel the road and the car and I have yet to see a road that turns my wheels for me.

A little wheel doesn't dake much energy to spin...