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ABS arguments

Here's my vote on the ABS issue:

[ Disclaimer for the thread-police:
 If you think NOISE follows, jump to the next  posting.
 If you think DATA  follows,  tell him to take his emotion-chip and shove it]


Anyway, I believe it is wrong to  assume all ABS systems were created equal. 

I have driven rental cars (Oldsmobuick or something) that  have  an ABS
system that is a joke.
These el-cheapo systems engage way too early, and brake pulsations are
between 0.5 to 1 second apart (big deal).

On the other hand you have advansed ABS systems like the one on the E36 M3 or
the 911. These cars have sophisticated  systems that allow utilization of ABS
on the track.

There are two  important issues here:
1)  Maximum braking efficiency of a rolling tire (and how do we get it ?)
2)  Maximum braking efficiency of a "locked" tire.

 The second issue is an easy one. Take your car and your test intruments on
the track and measure stopping distance (with locked tires) on a dry track .

Issue 1 (in John McLaughlin voice) is where all the confusion lies, and this
has nothing to do with ABS. 
What is maximum stopping efficiency for a rolling tire ?  A rolling tire has
maximum stopping efficiency  at about  (dont quote me on the number) 5%
before lockup. That 5% (I think) describes the brake pressure difference from
total wheel lock up. [Note that depending on the tire construction/compound
and real time car-suspension geometry/dynamics  the 100% brake pressure for
total wheel lock up will vary]

For example, a proffesional driver (and I am definetly not one!) knows
exactly how much pedal pressure will result in a lockup and how much pedal
pressure will result in a quick stop. On the other hand, a bad driver might
not aplly enough pressure on the pedal, thus extending his/her stopping
distance. In other words it is very hard to know, how hard to step on the
brakes in order to make the shortest possible stop.

Some drivers (again I am not one of them) know exactly how much is enough
pressure to lock up the wheels under different vehicle weight transitions.
These guys and gals know that when you are trail-braking less brake pressure
than normal will result in wheel lock up.

Getting back to the topic, the garden variety ABS systems are not
sophisticated enough to adjust the braking pressure to the optimal 95% of
total wheel lockup. Most ABS systems are crude enough to 
pulsate (reduce brake pressure)  at 80 % to 90% of total lockup. The stopping
efficiency of even a locked up tire is better than a 80% brake pressure. In
simple terms a locked tire on dry pavement can lead to better stopping
distances than a rolling tire under a el-cheapo ABS.

The E36 M3 is tuned very close to the maximum stopping efficiency of its
tire/rim combo. I bet the wife (not the farm), that nobody can beat the M3's
stopping distance (with stock tires) with ABS disenganged (on a dry and flat
 road). 

If anybody on this forum can shed some light on this issue and provide some
numbers/formulas it would be great help. The ABS=baaad , my foot=gooood
arguments are not very interesting.

Until then I will use my ABS will full confidence on dry (no flat spots) and
on wet (no head ons) roads.

 
Regards

Vlasis
Avus Blau