From: stecz@pencom.com (John Steczkowski)
Newsgroups: rec.autos
Subject: Re: Anti-Lock Brakes makes stopping SAFER?
Date: 30 Dec 92 19:52:56 GMT
Reply-To: stecz@pencom.com
Distribution: austin
Organization: Pencom Software

In article <16147@auspex-gw.auspex.com> tpickett@auspex.com (Tom Pickett)  
writes:
>....discussion about sliding sideways in an accident instead of headon...
> 
> The impact is lessoned to the extent of making it fairly reasonable.  this is
> all at low speed, and the scrubbing of the tires makes it even slower.

I still say sliding sideways in an accident won't lessen the impact.  Sliding  
sideways, you won't slow down as fast, because static friction is greater than  
sliding friction.  Try this some time, pull the fuse on your ABS, go out in a  
wet parking lot, and brake hard, notice how you are slowing down relatively  
fast, but when your wheels lock, you don't slow down as fast.  That is the  
difference between static friction (wheels not locked) and sliding friction  
(wheels locked).  No matter how you slice it, your tires have more traction  
when rolling than they do sliding.
> 
> It is not necessary to make statements like "I know you are a great driver,"
> I have no misconceptions about my ability to drive. I presume from your
> statement that you have autocrossed, so perhaps you feel you are a better
> driver than I, and you may be.  Perhaps I haven't been driving as long as
> you have either.:-)

This statement just backs up the fact that you are better off WITH ABS, you  
admit that you aren't that good of a driver, and haven't been driving for all  
that long, all the more reason that you shouldn't be trying "Dukes of Hazard"  
manuevers in a panic situation.  I do autocross, and I do think that it has  
improved my road driving skills, but it still doesn't allow me to disobey the  
laws of physics.

> 
> My concern is whether or not ABS is 
> necessarily the best thing to have in certain situations where it might
> be possible to reduce the impact of an accident in an unconventional
> way.

True, but you could also get hit by a meteor...

> I would not necessarily have taken longer to stop, I don't know.  There

It most likely would have (remember sliding and static friction).

> is a lot of drag created by sliding sideways on yuour tires, but I have

not as much drag as static friction

> to admit that such a maneuver is predicated on the assumption that an
> impact is imminent and not avoidable.  That I was able to stop in this

If the impact is imminent and unavoidable, you are better off hitting the  
object headon (assuming the option is to slide straight into it sideways and  
you can't have a glancing blow) that way the seatbelts, the cars crumple zones,  
airbag, etc can do the best job protecting you and your passengers from injury.

> case is a good point for ABS, but I'm not sure I would have been better
> off going straight into the offending car.  By spreading the impact
> over a larger area, I might have lessened the damage to the car.

In an accident, damage to the car is of secondary importance to the damage to  
the occupants of the vehicle.
> 
> Incidently I wouldn't use such a maneuver if the speeds were high or
> if I had a passenger.

We are talking about panic situations...Do you KNOW you wouldn't do it at  
highspeeds or with a passenger?

> I also wonder if ABS actually does stop a car any faster than a good
> driver can by simply modulating the pedal.  I also question the efficacy
> of ABS on slippery surfaces such as grass, snow, ice, etc... .
> 

This has been talked about over and over.  In IDEAL conditions, a GOOD driver  
can stop a car faster than the same car with ABS.  How often do you get in a  
panic situation under IDEAL circumstances, what if one side of the car is on  
gravel, and the other side on good pavement?  Can you keep the tires on the  
gravel from locking while maintaining maximum braking on the tires with good  
traction?  (retorical question, I already know that you can't)

> I think for commuting (ie, in heavy traffic) ABS is probably a good
> thing, but I definitely question its use under different circumstances.

This has been hashed over many times also, in deep sand, and deep snow, you are  
better off without ABS, because the material builds up in front of the tire and  
helps you slow down more.  A small amount of slush, or a little sand on the  
road won't build up in front of the tires, so you are still better off with ABS  
under these circumstance.

> Tom Pickett 
> tpickett@auspex.com or 74616.2237@compuserve.com
> SHO  GOZE

--
--
  John Steczkowski                        stecz@pencom.com
  "Achilles raised his spear, took careful aim, and hurled."
  					    from the Iliad