re: suspension tuning

[Joe Elliott <jee@domain.elided>]

At 10:40 AM +0000 11/18/02, alfa-digest wrote:
> A couple of mostly theoretical questions on suspension tuning:
>
> My 116 tends towards understeer when I'm pushing.  Trail-braking 
> into the corner it's fairly nicely balanced, but when I get back on 
> the throttle, it tends to push the nose wide, which I really don't 
> like.  I've never understood what's wrong with oversteer, or why 
> understeer is better.  I like a pointy front end, and a tail that 
> will give just slight oversteer that can be balanced with the 
> throttle coming out of the corner.
>
> Now, the traditional method for making the car more balanced would 
> be to stiffen the rear anti-roll bar and rear suspension.  This 
> would tighten the rear end, and the whole car would tend more 
> towards oversteer.  But would this be at the expense of overall 
> grip?  That is, would it be tending towards oversteer because the 
> tail was breaking away earlier than the speed at which it had 
> previously been understeering? 
> The other option is to soften the front end, through a lighter front 
> anti-roll bar, or removing the front anti-roll bar altogether.  (In 
> the local NZ Alfa Club, the most-stock racing series allows the 
> front anti-roll bar to be removed, as one of the few legal 
> modifications.)  So, a similar but opposite question -- if one 
> removes the front anti-roll bar in order to provide greater front 
> grip, and so reduce understeer, does it contribute to higher overall 
> levels of grip than a heavier rear anti-roll bar would? 
> Have I asked the question clearly?
>
> Kind regards,
> Anthony. 
> '85 116 Giulietta
It's hard to say what the effect on overal grip would be if you just 
stiffen the rear to make the car tend more towards oversteer.  I 
think you would end up with more grip because even though you're 
making the rear let go sooner (relative to the front), you're 
reducing body roll, which will allow you to use more of the available 
grip from your inside tires, hopefully more than offsetting the 
tendency for the rear end to break away sooner.  The reverse is true 
for removing the front bar--more roll, less overall grip.

Alernatively, you could increase the front caster to make the car 
tend more towards oversteer (and get marginally more overall grip). 
While the above paragraph is purely theoretical, I can tell you that 
I've done this to my GTV6 and the results are very noticable (ask the 
guy in the red GTV who almost hit me when I spun at the '01 USA AROC 
convention, having taken to the track for the first time since 
adjusting the caster).  After I put a slightly stiffer front bar 
(stock from an '89 V6 75/Milano) on my car it understeered more than 
I liked, and I've been able to neutralize the handling by fine-tuning 
the caster.  The effect on steering effort is negligible.

Hope that helps,
Joe Elliott
'82 GTV6 <--fastest GTV6 in Class D in the autocross at the '01 convention
'73 Opel <--has yet to move under its own power
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