Non ABS Car Purchase
10-28-2009, 03:03 PM
#31
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I could care less whether I have ABS. But, I'm very happy that my wife has it. The girl can't drive for poo, and cares not to learn. ;-)
PS: One driving aid that has AMAZED me in operation is stability control that applies brakes side-to-side to cancel yaw. THAT is something you can't do yourself and it really does add a margin of safety that no amount of driving skill can match (except the skill needed to avoid needing the stability control).
PS: One driving aid that has AMAZED me in operation is stability control that applies brakes side-to-side to cancel yaw. THAT is something you can't do yourself and it really does add a margin of safety that no amount of driving skill can match (except the skill needed to avoid needing the stability control).
10-28-2009, 03:16 PM
#32
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Yes in the snow the ESP in my Audi is amazing. Turn hard into a slick corner and it feels like someone tied a rope to the car and is swinging it around.
-Joel.
-Joel.
10-28-2009, 11:29 PM
#34
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Wow a wealth of information.. Thank you Cole and everyone else.. This will be a great thread for people searching for this information.. Appreciated!
10-28-2009, 11:41 PM
#35
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Two separate discussions: ABS use 1) on the street and 2) on the track:
1) There are certainly times on the street that ABS can increase stopping
distances. Primarily on snow/ice; slow speed complete stops can be very
bad. Extremely slippery surfaces, the tires are always at impending
lockup, so any application of brakes will cause the wheels to lock, ABS
kicks in, and you can literally roll through an intersection with your
braking foot on the floor. I don't mind having it in the rain, but it is
so seldom used. And in the dry, I can only think of one time in nearly 20
years of of driving ABS cars on the street, that I got into the ABS in an
accident avoidance situation.
2) I have yet to run into any circumstance on the track, where ABS is a
detriment.
The 87 Escort/Cup cars came with a pressure sensor mounted on the master
cylinder that would shut the ABS off at very high line pressure (it was extremely high - 160 bar), assuming that the driver had spun and had the pedal on the floor.
This was never added to later cars and I am assuming that it was because
it was determined to be unnecessary - since you can lockup all 4 in a spin
w/ ABS. Once the car lets go and you decide you need to put both feet
in, you may get a little initial ABS pulsing but once all 4 are locked the
ABS brain just sees all 4 wheels are stopped and for all it knows, the car
is not moving - so it doesn't pulse to break the lockup. I have
experienced this, unfortunately, more than once.
Can you offer a little more information here: was this on wet pavement or ice?
2-3 car lengths is approx 30-45 feet. Stopping distance for any
reasonable car from 20 mph wont be more than 30-40 feet, and likely a bit
less for any sports car with performance pads and tires. Are you saying
that a car with ABS turned-on takes more than twice the distance to stop
vs the same car/driver with the ABS shut-off on dry pavement?
What make and model of cars had a single channel ABS system? Bosch made
the first system that I am aware of, and the 944 was one of the early
production cars to offer ABS. And it does have 3 channel ABS - 3 lines
going out. Fronts work independently and the rear as a pair. All 4
wheels have sensors. If you really dive hard into the ABS on a 944, you
can feel the fronts pulsing independent of each other. Very, very seldom
will you ever have the rear ABS kick in.
I have never run into a 944 lifting an inside rear off the ground, and you
will never see a 911 have that problem. Its possible that you will get
light enough on the inside rear that under very severe trail braking it
might want to chirp/pulse the rear circuit, which could be a little
unnerving. If so, depending on track/car the driver would have to decide
to run with the ABS off to maximize trail braking, or leave the ABS on and
do a little more straight-line braking.
I very much agree that everyone should learn and practice braking w/o ABS.
But if the car has it, use it.
The ABS system is not holding brake system pressure or stopping power at
the stated 80% for any significant amount of time. The hydraulic unit
breaks the pressure in the line for only 100ths of a second, just to
release pressure in the caliper and get the wheel rolling again.
Now I have heard much discussion about the transition phase between
rolling and sliding friction, and the theory that the maximum coefficient
of friction is actually at some slight wheel slip, like 10-15% lockup
depending on tire brand/rubber compound, etc. And that street ABS systems
are not programmed to allow for this 10%+ slip, so they pulse prematurely
before this max friction point is seen. And it's a nice theoretical
discussion, but the reality is that on a real car on a real track, if you
are capable of braking an ABS car to the point of 99% of the available
traction limit, ABS will never kick in, and you will have identical
stopping distances.
ABS is helpful for when you exceed the traction limit, and lock a wheel.
It senses the locked wheel before you can, and pulses the line pressure.
You feel the pulse in the brake pedal, and if you want, you can then
"curl" your toes to back off from impending lockup.
The problem with braking to the limit of adhesion w/o ABS, and you can
have a ton of talent and practice it all you want, but the closer you are
to it and the harder you push, you will periodically exceed the limit and
lock a wheel. At the limit, car gets really sensitive to pavement and
other changes; any dips/bumps/cracks or patches will induce lockup. If
youre 2 feet off line in the brake zone, the surface is slightly
different. Doesn't take much at all for you to lock a wheel.
Not a big deal with a hard compound full tread street tire. But when
running very soft track compound tires, its very easy to flat spot one
before you have time to notice that you locked a wheel. And after
replacing a few hoosiers at $300 a pop, and having your car get a little
squirrely in a high speed braking zone w/ another car 24" away on your
inside, ABS is pretty nice to have.
And most will find that without it,
it is hard to maximize the brake effort consistently lap after lap. Half
hour into a sprint race, car is hot, tires are greasy, brakes are fading,
and concentration and focus are also fading. The rubber, oil, coolant or gravel
the car in front of you laid down in the brake zone, that wasn't there on
the previous lap - makes you tend to back off of the 99% braking limit,
and subconsciously protect the tires and the car.
1) There are certainly times on the street that ABS can increase stopping
distances. Primarily on snow/ice; slow speed complete stops can be very
bad. Extremely slippery surfaces, the tires are always at impending
lockup, so any application of brakes will cause the wheels to lock, ABS
kicks in, and you can literally roll through an intersection with your
braking foot on the floor. I don't mind having it in the rain, but it is
so seldom used. And in the dry, I can only think of one time in nearly 20
years of of driving ABS cars on the street, that I got into the ABS in an
accident avoidance situation.
2) I have yet to run into any circumstance on the track, where ABS is a
detriment.
Another thing I often wonder about is how ABS contramands the benefits of
going "both feet in." In an older, non-ABS car, both feet in locks up
the tires, and STOPS any steering forces. In a classic tank-slapper, that
could save you from darting into an inside wall. Basically, the tires
turn into big rubber erasers, and you proceed on a vector based on where
you were headed when they locked up, without regard to where the tires are
pointed.
But wouldn't ABS prevent this? If ABS stops the tires from locking up,
you WILL maintain steering force and the car will go where the tires are
pointed, which could be a hard spot across the track.
going "both feet in." In an older, non-ABS car, both feet in locks up
the tires, and STOPS any steering forces. In a classic tank-slapper, that
could save you from darting into an inside wall. Basically, the tires
turn into big rubber erasers, and you proceed on a vector based on where
you were headed when they locked up, without regard to where the tires are
pointed.
But wouldn't ABS prevent this? If ABS stops the tires from locking up,
you WILL maintain steering force and the car will go where the tires are
pointed, which could be a hard spot across the track.
cylinder that would shut the ABS off at very high line pressure (it was extremely high - 160 bar), assuming that the driver had spun and had the pedal on the floor.
This was never added to later cars and I am assuming that it was because
it was determined to be unnecessary - since you can lockup all 4 in a spin
w/ ABS. Once the car lets go and you decide you need to put both feet
in, you may get a little initial ABS pulsing but once all 4 are locked the
ABS brain just sees all 4 wheels are stopped and for all it knows, the car
is not moving - so it doesn't pulse to break the lockup. I have
experienced this, unfortunately, more than once.
2-3 car lengths is approx 30-45 feet. Stopping distance for any
reasonable car from 20 mph wont be more than 30-40 feet, and likely a bit
less for any sports car with performance pads and tires. Are you saying
that a car with ABS turned-on takes more than twice the distance to stop
vs the same car/driver with the ABS shut-off on dry pavement?
The other thing to consider on older ABS systems is
that it only takes 1 wheel to stop moving to trigger the release of brake
pressure to the WHOLE system. So a heavy corner entry the makes 1 rear
tire light can trigger a release of brake pressure to the other 3 wheels
that have great traction.
I have had many Porsches on a skid pad and you can watch and feel the
whole system release pressure to all the wheels on a set program.
Couple of other interesting notes. Many early systems were marketed as "3
channel" because they had 3 sensors, not because they could actually
control the front wheels independently. If you take a look at many early
ABS control modules you will see 2 brake lines leaving the module, not 3
or 4. This means that no matter how wheels have sensors on them, the most
the system could ever physically control is front/rear pressures.
that it only takes 1 wheel to stop moving to trigger the release of brake
pressure to the WHOLE system. So a heavy corner entry the makes 1 rear
tire light can trigger a release of brake pressure to the other 3 wheels
that have great traction.
I have had many Porsches on a skid pad and you can watch and feel the
whole system release pressure to all the wheels on a set program.
Couple of other interesting notes. Many early systems were marketed as "3
channel" because they had 3 sensors, not because they could actually
control the front wheels independently. If you take a look at many early
ABS control modules you will see 2 brake lines leaving the module, not 3
or 4. This means that no matter how wheels have sensors on them, the most
the system could ever physically control is front/rear pressures.
the first system that I am aware of, and the 944 was one of the early
production cars to offer ABS. And it does have 3 channel ABS - 3 lines
going out. Fronts work independently and the rear as a pair. All 4
wheels have sensors. If you really dive hard into the ABS on a 944, you
can feel the fronts pulsing independent of each other. Very, very seldom
will you ever have the rear ABS kick in.
A heavy turn and brake will put the weight firmly on 3 tires, causing only
1 to go light. The extra down force on the 3 tires is enough for full
control. But the light tire can trigger the ABS system into the preset
program that releases brake pressure to ALL of the wheels. Giving you the
opportunity to learn how to steer at a faster speed Up until the latest
high end ABS systems I would prefer to have a tire off the ground fully
locked up and drive with the other 3.
1 to go light. The extra down force on the 3 tires is enough for full
control. But the light tire can trigger the ABS system into the preset
program that releases brake pressure to ALL of the wheels. Giving you the
opportunity to learn how to steer at a faster speed Up until the latest
high end ABS systems I would prefer to have a tire off the ground fully
locked up and drive with the other 3.
will never see a 911 have that problem. Its possible that you will get
light enough on the inside rear that under very severe trail braking it
might want to chirp/pulse the rear circuit, which could be a little
unnerving. If so, depending on track/car the driver would have to decide
to run with the ABS off to maximize trail braking, or leave the ABS on and
do a little more straight-line braking.
If you learn what is known as "threshold braking". The act of braking up
to the 99 unit of traction point and holding it there you will have much
more stopping power than a system that is constantly releasing pressure
down to 80 units on you. It takes practice and a fine touch, but anyone
can become very good at it.
to the 99 unit of traction point and holding it there you will have much
more stopping power than a system that is constantly releasing pressure
down to 80 units on you. It takes practice and a fine touch, but anyone
can become very good at it.
But if the car has it, use it.
The ABS system is not holding brake system pressure or stopping power at
the stated 80% for any significant amount of time. The hydraulic unit
breaks the pressure in the line for only 100ths of a second, just to
release pressure in the caliper and get the wheel rolling again.
Now I have heard much discussion about the transition phase between
rolling and sliding friction, and the theory that the maximum coefficient
of friction is actually at some slight wheel slip, like 10-15% lockup
depending on tire brand/rubber compound, etc. And that street ABS systems
are not programmed to allow for this 10%+ slip, so they pulse prematurely
before this max friction point is seen. And it's a nice theoretical
discussion, but the reality is that on a real car on a real track, if you
are capable of braking an ABS car to the point of 99% of the available
traction limit, ABS will never kick in, and you will have identical
stopping distances.
ABS is helpful for when you exceed the traction limit, and lock a wheel.
It senses the locked wheel before you can, and pulses the line pressure.
You feel the pulse in the brake pedal, and if you want, you can then
"curl" your toes to back off from impending lockup.
The problem with braking to the limit of adhesion w/o ABS, and you can
have a ton of talent and practice it all you want, but the closer you are
to it and the harder you push, you will periodically exceed the limit and
lock a wheel. At the limit, car gets really sensitive to pavement and
other changes; any dips/bumps/cracks or patches will induce lockup. If
youre 2 feet off line in the brake zone, the surface is slightly
different. Doesn't take much at all for you to lock a wheel.
Not a big deal with a hard compound full tread street tire. But when
running very soft track compound tires, its very easy to flat spot one
before you have time to notice that you locked a wheel. And after
replacing a few hoosiers at $300 a pop, and having your car get a little
squirrely in a high speed braking zone w/ another car 24" away on your
inside, ABS is pretty nice to have.
And most will find that without it,
it is hard to maximize the brake effort consistently lap after lap. Half
hour into a sprint race, car is hot, tires are greasy, brakes are fading,
and concentration and focus are also fading. The rubber, oil, coolant or gravel
the car in front of you laid down in the brake zone, that wasn't there on
the previous lap - makes you tend to back off of the 99% braking limit,
and subconsciously protect the tires and the car.
10-29-2009, 12:06 AM
#36
Rennlist Member
Good post, Jim.
I mirror everything you say - I've never used the ABS on the street in an accident or accident avoidance scenario (in any car). On the street it only engages if I'm playing around (or in snow, ice, etc.).
On the track I experience it quite regularly - not only is it my indicator if I'm threshold braking, but, as you said, at the limit, with sticky tires, the slightest little variation in track surface can play a role. For example, it's not uncommon for me to get a little ABS pulse at the heel of the boot at Watkins Glen because the right front wheel has locked up momentarily due to a bump on the right side of the braking zone.
I'm glad I have it. I think it works well.
I mirror everything you say - I've never used the ABS on the street in an accident or accident avoidance scenario (in any car). On the street it only engages if I'm playing around (or in snow, ice, etc.).
On the track I experience it quite regularly - not only is it my indicator if I'm threshold braking, but, as you said, at the limit, with sticky tires, the slightest little variation in track surface can play a role. For example, it's not uncommon for me to get a little ABS pulse at the heel of the boot at Watkins Glen because the right front wheel has locked up momentarily due to a bump on the right side of the braking zone.
I'm glad I have it. I think it works well.
