How about (3)?
Get into the brakes as smoothly as needed to get the weight transferred to
the front end, then threshold just in and out of ABS.
Note: GM-specific stuff follows:
Obviously (I hope), if you slam on the brakes, it is possible to lock the
front wheels at a deceleration rate that is less than what it would be once
all the weight transfers forward and gives better grip up front. A problem
with the ABS on my '94 Z28 and my '89 Z51 Corvette and my '92 GMC Jimmy was
that once the ABS kicked in, that amount of brake line pressure was the MOST
you could get until you got off the pedal and the ABS reset. I'm not yet
clear on what happens with the ABS on my '99 Corvette, except that it makes
a hideous gravelly noise when it engages.
The most extreme case of this happened in the Camaro - if you were getting
into the brakes when the wheel(s) came unweighted, say over a bump, you
could get into a scenario where you had high, hard pedal, ABS active but not
cycling because there wasn't enough line pressure, AND THE CAR WASN'T
STOPPING!!! This happened perhaps a half-dozen times while autoxing the
car, including twice in a row at Santa Maria where I almost crushed Ralph
Elder into RX-7 ballast. It was also reproducible on a certain bumpy road
on the route home.
The effect is EASIEST to test on my Jimmy, because it takes so long for the
weight to transfer to the front end. If I stab the brakes, I can get into
ABS immediately, with very little (say 20-30%) deceleration taking place,
and no wheel lockup/ABS cycling happening at all. If I get into the brakes
smooth, fast, and deep, (say .5 - .7 seconds for that boat), I'm getting a
LOT more stopping power as the front end weights, and when ABS finally kicks
in it is actually locking/unlocking the wheels.
Realistically, on course I try to get as much weight transfer as I can, THEN
smoothly apply brakes until I'm "into" the ABS, then (if there's time) back
off just a tad and basically threshold there. In other words, I use the ABS
as a cheap alternative indicator to flat-spotting the tires. ;) Yesterday
on an autox school course I was getting into the ABS at full braking on each
corner of a rectangle course; that was partially running on street tires,
partially a sandy course, and partially still learning the car.
I encourage anyone, especially with GM vehicles, to go do some tests and
report their findings as well. I think ABS is A Good Thing, but using it to
fullest extent on course isn't quite as simple (for me, at least) as just
"nailing the brakes".
KeS
> Assuming that you are driving an ABS equipped car on course in a straight
> line at 50mph or so approaching a very tight hairpin, what is the best
> braking technique to slow the car down before entering the corner: (1) Hit
> the brake pedal as hard as you can thereby engaging the ABS and causing
> your tires to emit little puffs of smoke as they skid 1 foot at a time
> between ABS pulses, or (2) Brake only as hard as you think you can without
> locking up the wheels/engaging the ABS? I am not talking about braking in
> a corner. I'm just wondering whether you lose time by doing #1 by
> suffering the disadvantage of sliding friction over static friction, not
> to mention maybe overheating/flatspotting your tires. Which is the
> fastest way to get the car slowed down in a straight line?
>
> Any thoughts?
>
> Thanks,
>
> Rich Johnston
> 95 Z28 ESP
> NER SCCA
>
>
>
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