Alignment or Suspension Related at 100MPH?

MaysEffect

Both myths are not actual direct causes of tramlining for most cars, and the Z34 chassis in particular. The standard 225 and 245 front tires are not large by normal standards, certainly with the static weight applied to them. Nor is the wheelbase that short, it's longer than both the latest 911's and Caymans and a few other cars at 100 inches and only 8 inches shorter than the a E92 m3 which has a backseat and longer trunk.

As Jhill stated, increasing toe-in will help self centering, but at a cost of slower response with high lock and more tire scrub.

The predominant reason behind the tramlining and wandering is the Caster angles and anti-dive geometry. Camber and toe marginally changes this. From the 350z, Nissan reduced the caster angles by over 3 degrees, and around 3 degrees less than most cars nowadays with standard mcpherson strut designs (6.5-8.5 degrees compared to 4.5-5.5 degrees in the Z34).

This reduces the self centering steering notable in cars like the VW golfs, Ford Focus and 911's. For those who have driven the Alfa 4c will note that car wanders around and squirms over cracks a lot! This car has smaller tires, shorter wheel base and....dot dot daa.. less caster and more anti-dive A-arm tilt.