The suspension (archive)

Summary:
The objective was to have about -1 degree of camber front and rear. Body roll is limited with the 20mm touring rear bar and Dinan front bar. Ride is greatly improved over Dinan Stage III, even going to 18 inch wheels. Handling is neutral, tramlining nonexistant (on new tires). I have probably given up some ultimate grip, but would need testing with tire pyrometer to tell.

My car came with Dinan Stage III suspension and 255/40R17 Sumitomo HTRZ's on 17 x 8.5 ET15 Mille Miglia Glide II's. It handled fantastic on flat surfaces, but tramlined something fierce on the rutted "chip and oil" back roads they have here in Central Illinois. Also, the front end felt "floaty" although two mechanics assured me the struts were fine.

The thrust bushings had been recently replaced with 750 bushings and I had the alignment checked.

I pulled the springs, set the car on adjustible stands (screw type) using the factory jack locations, and front full droop, lowered the car 1/2 inch at a time. At each level I measured camber and toe for each wheel. There is a rapid change in rear camber that starts about an inch past the stock ride height. I concluded that the rear should not be lowered past factory. Also I found the front was riding ON THE STOPS. No wonder the ride was a little firm...

I concluded the tramlining was from excessive camber (-1.9 front and rear) as well as the wrong offset and too wide wheels.

Front suspension
Out came the Dinan springs, camber plate and front struts. One was a hydraulic insert, the other a gas strut. This would explain the difference in ride height side to side...

In went Koni Sports, factory M-Technic springs, -1/2 degree strut bearings and new rubber spring pads and bump stops. The Dinan bar is set on setting from full soft.

Rear suspension
Out came the Dinan springs and Dinan sway bar. I elected to keep the LAD as I travel with friends and family. LAD keeps you out of the nasty part of the camber curve.

Replaced one leaking shock, in went M-Technic sedan springs and Euro Touring sway bar (20mm). All rubber spring pads, bump stops and bushings were replaced, including the subframe bushings (this was the worst part of the whole job).

To reduce rear camber, KMAC urethane bushings were used for the trailing arm. The inside bushings do not play well with the offset bolt on M5's. I made it work by filing the flat off of hole in the bushing. If I had it to do over, I would use the factory offset rubber bushings set to reduce camber on the inside and use KMAC outer bushings set to reduce camber on the outside. This would allow me to adjust toe using the factory offset bolt, as it is I rotate the outer bushing, which changes camber too.

NOTE: KMAC bushings are wider than factory. I could no longer attach the pitman arms (dog bones). Frankly, they are no longer needed as the trailing arm is firmly located by the bushing while the factory bushing allowed it to slide back and forth. I believe the dogbones provide toe control with suspension movement, so I have reduced understeer, but increased rear bump steer. Also, I wanted to keep the diagonal brace on the right side, so I cut a dogbone in half to mount it.

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