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ABS and "straightening"

To: <ba-autox@autox.team.net>
Subject: ABS and "straightening"
From: "Josh Sirota" <josh@sirota.org>
Date: Sat, 17 May 2003 21:09:31 -0700
James wrote:
> i really
> only noticed it in a miata once, where the ABS would
> cause the car to
> straighten under braking.  (horrible feeling :-))

There's a reason for this.

Basically, the ABS works by allowing the tire to lock, and then backing off.
Although the tire is only locked for an instant (these things pulse very
quickly, like 20Hz or faster), during that instant the locked wheel will go
straight, just like any locked wheel.

So if cornering while using ABS, you will always require more steering input
than the same corner without ABS (and without any tire locking.)

When I did the Skip Barber Advanced Driving School in a previous lifetime
(before I started autocrossing), we did this very exercise in BMW M3s, and it
was very clear what was going on.

Josh

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