Southern GT rear wishbones

I have the southern GT rear end modification on my GTD. When the car is on its wheels with engine/box installed, should the lower rear wishbones be level with the bottom of the chassis or pointing slightly down towards the outside?
Simon
 

Mike Pass

Supporter
Hi Simon,
As a VERY rough guide the angle of the lower wishbone would be angled down and the upper wishbone angled up at a steeper angle (about twice the angle of the lower. The angle is measured from the centres of the pivots not the metal wishbone tubes themselves. The idea is that as the lower wishbone moves upwards in bump the outer pivot moves away from the car centre line and for the upper wishbone the outer pivot arcs inwards towards the car centre line. So the lower moves out and the upper moves in thus increasing the amount of negative camber. When the suspension droops the opposite occurs. So when the car loads up the outer wheel in a corner and the car rolls the suspension puts in more negative camber to keep the tyre flat to the road. The best way to find out is to make a cardboard model or use a computer suspension program to see what happens as the suspension rises and falls. The amount of camber change has to be tuned to the roll stiffness so as to keep the tyre at the right angle to the road.
The quickest way is the ask Mick Sollis as he has worked all this out. It seems to work well as Mark Hales was very favourably impressed with the handling of Glen Mason's SGT.
Cheers
Mike
 
Simon, depends on your chosen ride height, Frank
:huh:

I would start from the point where the geometry is intended to work in an optimum range. As Mike already pointed out the camber should increase on the outer wheel and decrease on the inner wheel to compensate for roll in the same ratio and keep the max tire surface on the track ( at least that´s the theory).
Mick will know at which angle of the lower wishbone this neutral starting point is. Oftentimes this sweet spot is achieved with a lower wishbone parallel to the leveled ground.
THus the rideheight is just a result of the lower wishbone at that optimum angle and the heigt of your tires. If you choose a lower profiled tire, the angle would still be the same, but the ride height lower.


TOM
 
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