🚀 go-pugleaf

In article <1992Dec3.013225.17152@mercury.cair.du.edu> jvilhube@diana.cair.du.edu (Jan Vilhuber) writes:
>In article <1992Dec2.171525.7518@ucsu.Colorado.EDU> knapp@spot.Colorado.EDU (David Knapp) writes:
>>In article <1992Dec2.030218.18970@ucsu.Colorado.EDU> lorenzo@spot.Colorado.EDU (Eric J. Lorenzo) writes:
>>>In article <1992Dec1.203832.3037@ucsu.Colorado.EDU> knapp@spot.Colorado.EDU 
>>>(David Knapp) writes:
>>>>If you do this, just remember, 4wd does wonders for acceleration in snow
>>>>and ice but does NOTHING OVER 2WD FOR STOPPING.
>>>>
>>>Hope this doesn't seem too basic of a question, but what about ABS brakes?
>>
>>Just drove a rental car this weekend up to Estes park that had ABS brakes.
>>They locked up as easily as another brakes. 
>>
>>ABS brakes only seem to make a difference if there is at least some traction
>>for the electronics to be able to sense slipping.
>>
>>>I am thinking they won't do anything on ice, but if the roads are just poor and
>>>the tires are getting some (even minimum) traction, they would stop the car
>>>faster then normal brakes.  4 wheel ABS would be the best so either axle
>>>doesn't lock up and spin the car anyway.  Does that seem right?
>>
>>I guess it would, but it is when conditions are bad when I need the best
>>braking. ABS doesn't help at all in the worst conditions.
>>
>>I hope that consumers don't take ABS as a panacea like they do 4WD.
>>
>>>
>
>Actually, If I understand ABS right, then its purpose is not to stop you 
>faster, but to keep you in control, since it prevents the tires from locking
>and thus slipping, which does nothing for steering (locked wheels don't steer).

The purpose is to keep the wheel from locking. Anti Lock Brakes. If ABS
system is working, the wheel will be braking as much a physically possible
*without* actually locking. The reason this is beneficial is that the 
dynamic frictional coefficient is invariably less than the static frictional
coefficient, which is something most drivers seem to be missing.

Therefore, ABS *should* stop you faster and *should* keep you in more real
control. What we have established is that this only really works on roads
which are not that bad to begin with.

Remember the frictional coefficient. If you are stuck in snow, you will
actually stay stuck longer if you let your wheels spin. I see so many
people gun their cars when they are stuck and this only makes their traction
much worse. The best traction occurs when the wheel is not slipping. When
you are *stuck*, take avantage of those seconds where the wheel is *not*
slipping.


>
>I've always sort of wondered why bother with ABS, since I presume that it
>would LENGTHEN your break-distance, since it makes the breaks 'stutter'.

Preventing locking up, while still braking to just the locking point, 
provides the maximum attainable braking and minimum attainable braking
distance. This is why they are put in cars to begin with.

>You can just as easily do that yourself, if you are a good driver, plus you
>get the advantage of NOT having it on a dry road, where slipping is not 
>a (major) factor, and thus a shorter breaking-distance.

Humans do not have the ability to sense "impending skid" which is why
a computer does that job for you in ABS cars.

You cannot just 'try harder' and beat a good ABS system.
-- 
David Knapp                                      University of Colorado, Boulder
Perpetual Student                                   knapp@spot.colorado.edu