Several things, either individually or collectively are causing this... Prime suspects for me are the tires. Some wider-than-stock tires (like my own 225/45R17 fronts) make my car tramline badly on some worn surfaces (wander and "surf" any rut in the road), but other than that is very stable. Some same width tires have less tendency to tramline. Second suspect is the steering gear. If you have any dead spot (free play) in the steering gear, the tramlining and car steering itself feeling will be magnified. Also, any slop in the steering linkage from tie rods to idler will also rear their ugly heads. Third suspect is alignment. What are your alignment specs? I'd probably shoot for at least +3° caster, 0 to -1° camber and 1/8" total toe with your mods. Other issues some will have are worn strut rod bushings, Granada brakes in some cars (a few have noticed an increased tendency to bumpsteer in a few cars) or worn control arms/ball joints.
When did you notice the steering issue? Has it gotten worse over time? Are there some conditions it is noticed more than others? Good luck with the troubleshooting. Let us know what you find out.
Daniel
I should add that you should check out http://www.stangerssite.com if you need your gear rebuilt. He'll rebuild your steering gear for ~$150 or so, which is pretty cheap for the job he does.
is it just me, or does HTTP://www.stangersite.com take you to a mail login site? I tried links to same site posted on other forums and it did the same thing.
I had my whole steering system rebuilt and it still wondered... I learned that I needed to run more caster than factory spec because of the difference between bias ply and radial tires.... adjusted the strut rods and viola - no more wondering. I'd start there.
Second thing to try is tighten up your gear. There is a bolt on top that can be tightened to tighten the meshing of the gears. Not sure exactly how to do it but I'm sure someone does...
I had my whole steering system rebuilt and it still wandered... I learned that I needed to run more caster than factory spec because of the difference between bias ply and radial tires.... adjusted the strut rods and viola - no more wandering. I'd start there.
Second thing to try is tighten up your gear. There is a bolt on top that can be tightened to tighten the meshing of the gears. Not sure exactly how to do it but I'm sure someone does...
There's a set of instructions on the Stangerssite.com website. I haven't tried it (yet), but it looks fairly simple to do. Just be careful you aren't masking worn gears, though. You'll be back where you started pretty quickly.