Geometry Analysis - Measurements
Geometry Analysis - Measurements
(OP)
Does anyone have any thoughts regarding how accurately the locations of the suspension pivots need to be measured for input to a kinematics analysis program to yield useful output?
This is on a production car, I'm neglecting compliance for right now, and I have all the parts off the car and the balljoints disassembled (so I can measure the distance from the ball center to whatever). I figure measuring on the workbench I can count on accuracy within a 0.1 inch range for balljoints but some of the rubber pivots may take some guessing (e.g. the front upper strut mounts). Right now I'm using Susprog3D.
Thanks,
Hutch
This is on a production car, I'm neglecting compliance for right now, and I have all the parts off the car and the balljoints disassembled (so I can measure the distance from the ball center to whatever). I figure measuring on the workbench I can count on accuracy within a 0.1 inch range for balljoints but some of the rubber pivots may take some guessing (e.g. the front upper strut mounts). Right now I'm using Susprog3D.
Thanks,
Hutch





RE: Geometry Analysis - Measurements
However, the quick answer is that if it is a fairly bread and butter suspension 0.1" is a bit on the high side, but should give you the right trend, with the exception of the toe curve.
In production the vertical relationship between the lower arm inner mounting, and the steering rack, might be set to within 0.020". This sets the toe curve.
Oh, what sort of suspension is it?
Cheers
Greg Locock
RE: Geometry Analysis - Measurements
The suspension is McP strut with the L-shaped control arm in the front and trailing arm with upper and lower lateral links in the rear. I'm investigating the differences in the regular and "motorsport" versions of the car, and what was changed through the life cycle of the models.
Granted, I won't be able to reverse engineer the whole thing but that doesn't really matter. I'm looking at it from more of a race car prep perspective, trying to figure out the effects of common modifications such as offset bushings, strut mount modifications for more negative camber, etc.
As a side item, any thoughts on changing KPI on a strut front suspension? It looks like increasing it makes the camber curve a little steeper but what about negative effects for steering feel and camber loss with steering (assuming all other parameters are unchanged)? Maybe the KPI discussion deserves a thread of its own.
Hutch
RE: Geometry Analysis - Measurements
Cheers
Greg Locock