Porsche Stability Management

[Sammy]

You guys must have had too many marsupial turds in your coffee... (I'm kidding, I just like using the phrase "marsupial turds"... kind of catchy)

In theory ABS is slower than non-ABS (I completely agree with this); however, a human being cannot break faster than ABS with any level of consistency regardless of skill. You can put Andretti, Montoya, Bondurant, etc, in the same car and let them stop in a straight line 100 times and if they are lucky they just might be able to outstop the ABS a few times. Put them in a turn and the liklihood decreases because the weight shift is much more complicated. As you have mentioned ABS pulses faster than any human being could consciously "lift" off the pedal due to the reaction time. There is no such thing as a zero second reaction time that when a driver recognizes the wheels locking up that he/she can instantaneous lift and reapply the brakes. On the other hand a skilled driver cannot consistently stay at the edge of locking the wheels... He/she can do it better than we can, but not faster than ABS.

I completely agree that it hinders the development of a driver because it acts as a crutch, but it also keeps people safe. We also aren't driving million dollar cars that if we wreck them a sponsor pays for a new one.

[funster]

Sammy, you are mistaken, the abs senses a skid and begins its pulsing and won't stop pulsing until it senses that all skidding has stopped. Once this happens your stopping power depends on when the wheel with the least traction stops sliding. Try this test if you ever have a car in the snow(and you are confident that you can do it safely). Drive with one side of the car on a plowed surface with good traction and the other side of the car on a slippery part and apply the brakes to activate the abs. You'll see it takes significantly longer to stop than if the wheels on dry pavement could utilize all their traction. (some abs systems are better at this test than others) The same principles are true on a race track when cornering. if you hit a small bump on a wheel on the inside of your turning circle and set off the abs you can decrease the ablity of your car to brake and fairly skilled drivers can do this better than the abs which is why they don't put abs on race cars.

[Sammy]

Originally Posted by funster

Sammy, you are mistaken, the abs senses a skid and begins its pulsing and won't stop pulsing until it senses that all skidding has stopped. Once this happens your stopping power depends on when the wheel with the least traction stops sliding. Try this test if you ever have a car in the snow(and you are confident that you can do it safely). Drive with one side of the car on a plowed surface with good traction and the other side of the car on a slippery part and apply the brakes to activate the abs. You'll see it takes significantly longer to stop than if the wheels on dry pavement could utilize all their traction. (some abs systems are better at this test than others) The same principles are true on a race track when cornering. if you hit a small bump on a wheel on the inside of your turning circle and set off the abs you can decrease the ablity of your car to brake and fairly skilled drivers can do this better than the abs which is why they don't put abs on race cars.

I vaguely remember that Formula 1 use to allow ABS and banned it...

I agree that ABS is not faster in all situations.

[racer_d]

Originally Posted by funster

... which is why they don't put abs on race cars.

Yes and no. The use of ABS on a race car is dictated by the sanctioning body, not the race car maker. Many series don't allow it for 1) "man vs machine" arguments as to who is doing the actual driving - driver or car; 2) Cost ; 3) Potential for using the ABS to do other things (like a traction control or Stability management program which would give the car an unfair advantage)

Porsche (with the help of Bosh) has developed some very advanced and capable ABS brake systems. Their systems actually allow a certian percentage of "lock" that is dialed out of a street cars ABS system.

ABS doesn't always improve or hurt a cars stopping distance (there are way to many variables to discuss here, like the one above about driving on snow and clear pavement at the same time) but it DOES make a car safer, since it allows one to maintain STEERING capabilities to aviod accidents.

[MNBoxster]

Originally Posted by racer_d

Yes and no. The use of ABS on a race car is dictated by the sanctioning body, not the race car maker. Many series don't allow it for 1) "man vs machine" arguments as to who is doing the actual driving - driver or car; 2) Cost ; 3) Potential for using the ABS to do other things (like a traction control or Stability management program which would give the car an unfair advantage)

Porsche (with the help of Bosh) has developed some very advanced and capable ABS brake systems. Their systems actually allow a certian percentage of "lock" that is dialed out of a street cars ABS system.

ABS doesn't always improve or hurt a cars stopping distance (there are way to many variables to discuss here, like the one above about driving on snow and clear pavement at the same time) but it DOES make a car safer, since it allows one to maintain STEERING capabilities to aviod accidents.

Hi,

You're quite right about the sanctioning bodies, but of course, these change their rules and tech requirements often from the cumulative pressure of sponsors and competitors.

ABS will almost always hinder a car's stopping abilities, it's inherent in how it works though I concede there are many variables to consider.

No arguement about ABS's ability to preserve the steerability of the car, but that arguement requires that the Driver actually use this capability to steer away from the trouble and as I stated, as a rule, Drivers are not taught to do this or how. Consequently, there is no statistical data showing significant accident reduction due to the advent and adoption of ABS...

Happy Motoring!... Jim'99

What car stops fastest on a sheet of ice?

With ABS or without ABS??

Hypothetically, all this being equal.

I gotta believe with ABS...been there ...done that!

[MNBoxster]

Originally Posted by bmussatti

What car stops fastest on a sheet of ice?

With ABS or without ABS??

Hypothetically, all this being equal.

I gotta believe with ABS...been there ...done that!

Hi,

as racer-d stated many variables to consider. But, generally, here I agree with you that ABS, if not stopping in a shorter distance altogether, will not be as far behind a non-ABS system than on dry pavement. But, realize that here too, it's main advantage will be one of maintaining control...

Happy Motoring!... Jim'99

[racer_d]

Originally Posted by MNBoxster

Hi,

You're quite right about the sanctioning bodies, but of course, these change their rules and tech requirements often from the cumulative pressure of sponsors and competitors.

ABS will almost always hinder a car's stopping abilities, it's inherent in how it works though I concede there are many variables to consider.

No arguement about ABS's ability to preserve the steerability of the car, but that arguement requires that the Driver actually use this capability to steer away from the trouble and as I stated, as a rule, Drivers are not taught to do this or how. Consequently, there is no statistical data showing significant accident reduction due to the advent and adoption of ABS...

Happy Motoring!... Jim'99

Seems we agree! It would make sense that some people avoided accidents because of the ABS providing them the ability to avoid an accident, thus not providing any imperical data that ABS did not reduce the number of accidents.

I would say that now that ABS has been around for nearly 20 years in passenger cars, even if people learned "by accident" of its advantages it is something that SHOULD be on a passenger car. Race car? maybe not.

I love to threshold brake as much as the next would be racer when i am at the track.

Then again, the discipline to apply only threshold braking without locking them up, when another car is suddenly stopped in front of you, or in your lane etc, is very hard to master. Frist thought is "stop" car ASAP.. mash brakes to accomplish.. get "deer in the headlights" syndrome and hit the vehicle/object you were trying to avoid.

Years of Drivers Ed/Autocross events and experience in general has taught me that sometimes "stopping" isn't the best option. Steering is... sliding is... accelerating is.. As mentioned, way to many variables to come up with 1 rule for all instances.

I will enjoy the ABS my new car has for DE/AX events. I will enjoy it on the street. But thank goodness my car doesn't have PSM so I can still enjoy sliding her around

[MNBoxster]

Originally Posted by racer_d

Seems we agree! It would make sense that some people avoided accidents because of the ABS providing them the ability to avoid an accident, thus not providing any imperical data that ABS did not reduce the number of accidents. I will enjoy the ABS my new car has for DE/AX events. I will enjoy it on the street. But thank goodness my car doesn't have PSM so I can still enjoy sliding her around

Hi,

Since we each have some considerable Track experience, I'm not surprised that we agree.

One small point though, your hypothetical about the accident which didn't happen and therefore not added to the Ins. Stats may be valid. But, the ins. statistic of rear end collisions/mi. driven remains unchanged since the advent of ABS. So while I am also sure that some accidents have been avoided due to ABS and not reported, not enough to positively impact the statistics. The rate remains the same...

Happy Motoring!... Jim'99

[Sammy]

As always, I appreciate the respectful discussion of a contested claim.

For what it's worth, my claim is not from my own making but simply regurgitating a statement that was made from one of those three names that I threw out there. I happened to have the opportunity to ride/drive a S2000 around a handling course with one of those experienced racers and the question was directly asked "can you brake faster than ABS?" The response was the statement I made... This was supported by another person who has written vehicle dynamics books and trained countless people on the theory of maximum handling.

Every formula 1 race I've ever seen (road course) has had numerous instances where a driver slid a wheel and ended up too far in a corner resulting in losing a place and many times wrecking the car. If anything they become conservative in braking because they can't afford to lock a wheel. This is where the driver skill comes in and separates the men from the boys...

Originally Posted by funster

Sammy, you are mistaken, the abs senses a skid and begins its pulsing and won't stop pulsing until it senses that all skidding has stopped. Once this happens your stopping power depends on when the wheel with the least traction stops sliding. Try this test if you ever have a car in the snow(and you are confident that you can do it safely). Drive with one side of the car on a plowed surface with good traction and the other side of the car on a slippery part and apply the brakes to activate the abs. You'll see it takes significantly longer to stop than if the wheels on dry pavement could utilize all their traction. (some abs systems are better at this test than others) The same principles are true on a race track when cornering. if you hit a small bump on a wheel on the inside of your turning circle and set off the abs you can decrease the ablity of your car to brake and fairly skilled drivers can do this better than the abs which is why they don't put abs on race cars.

Hey Funster, in your example (one side on snow one side on pavement) at least the car will track reasonably straight...right? At least this has been my experience. And an advantage of a car with ABS.

[funster]

No Question, wirh the abs the car will track straight and will tend to pull without abs to the side with traction. Abs is great on slippery surfaces to preserve the directional control of the automobile, of that there is no question and as a safety feature, it's tops. Porsche brakes are fantastic and it's seldom that the abs activates as I try to stay just below that point. Abs has come a long way from its early days and I'm sure that it's only a matter of time before it will surpass the abilities of even the finest of drivers.

My daily driver is an SUV (Explorer XLT Sport 4x4) and the ABS is kicking on every day! ABS is great on wet leaves too. Those buggers are slick.

[MNBoxster]

Originally Posted by Sammy

...In theory ABS is slower than non-ABS (I completely agree with this); however, a human being cannot break faster than ABS with any level of consistency regardless of skill. You can put Andretti, Montoya, Bondurant, etc, in the same car and let them stop in a straight line 100 times and if they are lucky they just might be able to outstop the ABS a few times. Put them in a turn and the liklihood decreases because the weight shift is much more complicated. As you have mentioned ABS pulses faster than any human being could consciously "lift" off the pedal due to the reaction time. There is no such thing as a zero second reaction time that when a driver recognizes the wheels locking up that he/she can instantaneous lift and reapply the brakes. On the other hand a skilled driver cannot consistently stay at the edge of locking the wheels... He/she can do it better than we can, but not faster than ABS...

Hi,

Sorry, not buying it. I have demonstarted this and seen it done by professionals. ABS is not even designed to decrease the stopping distance, it's sole purpose is to prevent wheel lock, it does not increase the brakes efficiency. In fact, because the calipers are not clamped continuously (where mechanical energy is transferred to heat energy and expelled from the system), it reduces the brakes efficiency and results in longer stopping distances. And this says nothing of where the threshold is set by the control unit. It can be argued that if you activate the ABS at all, you're already doing it wrong. It is possible to understand and feel when the car will lockup and thereby avoid it...

Happy Motoring!... Jim'99