[A4] tires, speaking of tires, anyone have any used 17's lay'n around?

[Brett Dikeman]

On Dec 27, 2007, at 7:22 PM, LL - NY wrote:

> Hate to point this out, but the wheel(s) that are triggering ABS are  
> being used to
> the maximum point of availible braking traction, within the limits  
> of the ABS computer
> and pump, which is nowhere near lost braking. I'd estimate that even  
> the early Bosch
> series 1 ABS is capable of using nearly 70% the availible braking  
> traction for the activated
> wheels. And, in the case of the type 44 and C4 cars, loosing the  
> rears will hardly affect
> things, they're not doing too much braking anyway (virtually no  
> traction due to weight
> transfer) in a threshold situation.

ABS is not for shortest stopping distance.  It's for avoiding loss of  
directional control from braking- ie spins or directional loss of  
control from uneven braking side-to-side.  That it also provides a  
function which *approximates* threshold braking on dry pavement, is a  
nice bonus; dry pavement is more suited to the way ABS controls the  
brake.

In slippery conditions, ABS is best left as a safety net, because it  
doesn't have nearly the 'gentle touch' required.  My 200q20v's ABS is  
almost completely useless in the snow for actually stopping the car,  
and my folks' Volvo was the same way.  Both vehicles, regardless of  
tire choice, could stop far shorter when the nut behind the wheel  
applied juuuuust enough brakes.  I'm sure most listers have noticed  
the same, if they've ever messed around in a parking lot or just  
tested how much traction was available on the road (something I  
recommend listers do often in slippery conditions for a sense of  
braking capabilities.  I've been very surprised in both ways by  
conditions- I've been in heavy snow that let me stop on a dime, and  
light snow that was slippery as hell.)

At the track or on the street, it's much the same story.  You can slam  
on the brakes and generate a lot of drama, or you can surely apply  
them and STAND on the brake pedal without engaging ABS.  You've giving  
time for the weight transfer to start, for the suspension to load up,  
etc.

I also spent a few years watching attendees do the "panic stop with  
ABS vs. threshold braking" test at WDS.  Even with a basic amount of  
instruction and a few practice goes, a driver can easily and handily  
beat ABS, and it's clear as day when they're standing on the pedal-  
even with snow tires, the wheels stop/start, the car wobbles,  
and....doesn't do a very good job of stopping.  You can even tell when  
some transitions from threshold braking to "oh #@$!" foot-on-the floor  
(one of the informal and optional "contests"

Brett