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RE: standard ABS test
From: Peter Zangl ZNGL
Subj: RE: standard ABS test
Fred Yip <fred@domain.elided> wrote:
>> Just a word of caution, this test can land you in BIG trouble. A BMW
salesman
>> rolled my fathers 320i before he took delivery by showing a customer how ABS
>> handles this test.... If the car has different amounts of traction on the
left
>> and right, you are going to get the car trying to rotate - ABS will help you
to
>> correct, if you are quick enough.
>I thought ABS only prevents wheel lockup. It does not compensate the
>difference in traction. This "standard demo" has been used by Audi to
>demonstrate quattro 4wd. I believe Porsche did the same thing to show
>its traction control feature on the 928's.
I'm no expert, but this is what I think to know about it:
ABS doesn't compensate traction. This would mean that the wheels on the
dry side only brake with the same rate as the wheels on the dirt side
of the road. ABS only prevents the locking of each wheel, so you can
steer while breaking full. The effect is: The wheels on the dry side have
more traction, the car decelerates harder on this side and therefore it
steers in this direction. The salesman should have been able to steer
against it and keep control. Pitty, that he crashed a nice car. :(
What Audi and Porsche showed in their demo is completely different. They
showed the advantages of AWD/traction control when ACCELERATING. Quattro
gives more traction but the driver has still to compensate the difference
between both sides for himself. Traction control does this automatically.
It decreases the tourque on the dry side till both wheels get nearly the
same torque.
Hope this was right. Any corrections are welcome.
Peter Zangl
zngl@domain.elided
P.S.: Yep. I'm new here. Greetings from Bavaria and my '90 325i (E36)!