Steering/Tire Wander

[charlie]

Has anyone else experienced what I'll call tire wander on highway driving where the steering wheel seems to just pull hard in either direction when encountering less than perfectly smooth pavement or on roads that are "truck-rutted". I have experienced this with both my SVX's and have asked my mechanic who says it's just the nature of a 225mm tire. I just went touring through NJ this weekend and noticed it especially badly on Route 78 near Newark and on the Turnpike. Any thoughts/solutions/similar experiences.