Caster

["Graham Hilder" <graham.hilder@domain.elided>]

In no.1205, David wrote:
"As far as caster goes, most modern automobiles require positive caster,
>meaning the centerline of the kingpin axis is farther back at the =
top...... A car with too little positive caster will run right off the =
road if you let go of the wheel, but will turn in better, understeer =
less...... Too much positive caster will cause heavy steering at low =
speed, (and)  understeer....... "

And Greg wrote:
"Steering self-centering effect, directional stability, turn -in feel, and
the like are affected primarily by CASTER......=20
A caster angle LESS than the kingpin inclination angle will give an
increase in positive camber on the outside wheel as a car is steered into =
a turn, giving a tendency toward understeer. (And, vice versa.)....."

On these postings, I was surprised to read David's remark that too much =
caster would cause understeer, and re-assured to read Greg's indication to =
the contrary, i.e. that increasing caster would (generally) tend to give =
less understeer. I remember a wheel-alignment man I once went to reckoned =
that I shouldn't spend too much time experimenting with yet more neg =
camber to reduce my understeer..... no, he said, go for more caster, =
that's where it's at. And it does seem inuitively right, in a general way =
on an average suspension layout, that with more caster, you'll gain more =
neg camber as you turn the wheel, hence achieving the desired result. =
Unfortunately, on the car concerned, the caster isn't adjustable (without =
considerable mods), so I haven't been able to try it out in practice.

Regards,
Graham in NZ
(71 GTV, 77 Alfetta, 82-82-84 Alfasuds)

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