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Re: [Mgs] Tagged a tyrewall

To: Eric Erickson <eric@erickson.on.net>, MG List <mgs@autox.team.net>
Subject: Re: [Mgs] Tagged a tyrewall
From: Barney Gaylord <barneymg@mgaguru.com>
Date: Thu, 16 Jun 2011 18:08:45 -0500
Yup, I got the answer.  Nice video.  You were driving, so it's your 
fault.  The car doesn't handle well, and you didn't handle the 
cantankerous car well either.  It's one of those things where you 
have to drive whatever is put in your hands, and fix the handling 
problem later.

It starts in the first turn at the 8-second mark when you get the LR 
tire off the ground, followed immediately by oversteer and squeal 
from the overloaded RR tire.  You caught that one, tturned the 
steering wheel quickly right to keep the nose going in the right 
direction, and got your foot right back on the throttle to keep it 
straight.  But you should have gotten the message from that 
trick.  On the next turn you got the same thing at the 38 second 
mark, a little body roll, LR tire up, oversteer, and RR tire squeal 
as it goes sideways.  You caught that one too, turned the steering 
wheel quickly right to keep the nose going in the right direction, 
but you over did the steering correction, didn't bring the wheel back 
soon enough, and didn't put the throttle down, so you got immediate 
and accentuated oversteer in the other direction (fish tail).  When 
that gets out of hand you're going backward, and the game is over.

You have a real quick autocross car there that will turn in quick and 
oversteer on demand, but that's not the fastest way around a long 
curve.  What you need is more front sway bar (or less rear sway bar) 
intending to keep the inside rear tire on the pavement to prevent 
overloading the outside rear tire.  If you over do the front sway bar 
you can end up with understeer and push in the corners, also not the 
fastest way around the track.  For road racing you want near neutral 
steering for the highest speed in a long constant radius turn.  Then 
lifting off the throttle makes it turn in better at the entry point, 
and back on the throttle kills the oversteer and drives the front end 
to the outside of the curve.  (Just don't step too hard on the 
throttle when one rear tire is off the ground).

Barney Gaylord
1958 MGA with an attitude (and a house full of autocross trophies)
http://MGAguru.com


At 01:41 AM 6/17/2011 +0930, Eric Erickson wrote:
>I keep studying this video and I am really not quite sure that my turn into
>this corner caused this incident.
>
>It is the third lap I have run at this racetrack since 2006 - so I was
>certainly out of practice, but to have the rear tyres let go like that was
>really unexpected.
>
>Any thoughts?
>
>http://www.youtube.com/watch?v=Y7eaUaoP-ME
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