I replaced the tires on my Sunfire '03 with some that have more rigid sidewalls and find a bit of wandering at high speed. It depends on the road surface and adjusting the pressure has helped. It isn't dangerous, just annoying. It feels like how I've read tramlining described. Does anyone have a similar experience? Can I fix this "tramlining" by adjusting the steering rack in some way?
No.
Its just something you get used to...
I find different tires will do it more and less.
I have also read that adjusting your toe to roughly 1.5* in will help it as well.
Bad strut mounts I bet and or alignment is out.
see ya!