On Sat, 14 Feb 2009 00:40:06 +0200, Eero Ahonen wrote:

> Jim Henderson wrote:
>> On Fri, 13 Feb 2009 13:53:30 +0200, Eero Ahonen wrote:
>> 
>>> Yes, also on drum brakes. But why on earth would you engage brakes
>>> fully, if you're not trying to stop the car as quickly as possible?
>> 
>> Because slamming on the brakes on ice doesn't have that effect.
> 
> True, but the optimal braking with almost locked tires is pretty hard
> thing to do - usually it's much wiser to just hit the brakes fully, if
> you're trying to stop the car ASAP for some reason.

On dry pavement I'd tend to agree, though I have been known to combine 
the brakes and steering; two options, get out of the path of whatever it 
is that you are going to hit (or is going to hit you) and stop as quick 
as you can.  Gotta be careful, though, because that kind of reaction can 
cause a rollover if you're not careful.  The objective is to keep all 
four wheels on the ground in a situation like that - wheels in the air 
don't do anything for braking or steering.

>> I don't do it on ice.  You can (and I can) lock the wheels driving at
>> 50 MPH with the brakes, but that also is likely to cause an
>> uncontrollable skid - though a shorter one - and often that is more
>> desirable than running into whatever it is that you're braking hard to
>> avoid.
> 
> Yep, and the same laws work also on ice and on snow, braking distances
> just grow even exponentially.

How well I know; having learned on ice and packed snow, for the first few 
days on dry pavement, I misjudged stopping distances pretty badly.  
Fortunately, I was a quick learner and didn't have any accidents.

Jim

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