Alignment or Suspension Related at 100MPH?

Need4Speeds

So the factory tires with the hard sidewalls is what's causing the issue?

SouthArk370Z

Wide tires make tramlining worse. A short wheelbase makes tramlining worse. A light car makes tramlining worse. If you're going to drive a 370Z, you're going to have to put up with tramlining on rutted roads.

The Z has speed-sensitive steering. If you are encountering the problem on flat roads, this feature may not be working properly on your car.

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Need4Speeds

I'll take into service and have them check it out. Thanks.

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.

Jhill

Exactly, I was leaning towards the caster already but honestly don't feel it to be that bad in stock form so thought he might be feeling something else. However every car I've had has had a quicker go kart feel so I must not mind it but compared with the MB's and other lines I work on in the past, MB being some of the highest with their 8-9 degrees (this is going of memory) the z has very little caster.

TreeSemdyZee

Tire pressure comes to mind also.

What are you running?

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