James,
Are you talking about king pin inclination (KPI) or Caster?
KPI determines KPI trail, also called scrub radius. KPI is the angle
between the upper and lower ball joint centerlines as viewed longintudanlly.
Increasing KPI trail increases kick back through the steering wheel when the
tires
are subject to aysmetric forces. For this reason, when
ABS became real common most cars went to KPI angles that gave very
small scrub radii to minimize the kickback to the steering wheel under ABS
activation.
KPI is usually not adjustable and that is why when you change the
stock wheel offset and theefore change the KPI trail you can get
more kickback from the ABS (and more torque steer on front driver cars).
Caster is the rearward inclination of the axis between the ball joints
and is adjustable, within limits, on most cars. This is what causes camber
gain when
the wheel is turned (and also lifting you mention).
It's primarily there to increase straight line stability and the higher
the caster trail the more restoring force returning the wheels to straight
ahead while
in motion. The camber gain is ususally a side benefit for handling whereas
the lifting is a side detriment.
So, I don't see where a large spindle inclination is in and of itself
going to cause handling problems. Look at the scrub radius,
caster, static negative camber, toe, roll centers, springs, shocks, camber
curves, tires, rim sizes etc. to determine why your car isn't handling the
way you want it to.
--- Rick Brown
BP Corvette
> > 650-704-0771
> >
> > -----Original Message-----
> > From: owner-ba-autox@autox.team.net
> > [mailto:owner-ba-autox@autox.team.net] On Behalf Of James Creasy
> > Sent: Sunday, February 16, 2003 11:53 PM
> > To: ba-autox@autox.team.net
> > Subject: fatal flaw in my car?
> >
> > someone pointed out that my car has a very high Spindle Inclination
> > Angle,
> > about 15 degrees. this apparently causes my negative camber to go
> > positive
> > when i turn the steering wheel (plus it jacks up the front of the car),
> > and
> > is likely the cause of the huge amount of understeer i get exiting
> > corners
> > (recently i noticed it entering corners too). this is really
> > depressing,
> > since i think my only choice is to remount the upper a-arm lower and
> > make a
> > new bracket for the spindle to position the ball joint inside the
> > wheel...
> > which also means i cant use my 15" wheels.
> >
> > what is an acceptable amount of SIA for an autocross car?? any other
> > ways
> > to compensate for it?? thanks,
> >
> > -james
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