I'd suspect bent wheels or out-of-round tires.

Easy to check: jack wheel off ground, handbrake off. Move an object (say a
box) close to the wheel, with a corner almost touching at a point on the
rim edge. Lay or tape a pencil on top of the box, with its tip extending
out toward the wheel, to act as a reference. Rotate wheel. If bent, you'll
see it move toward/away from the pencil tip, either sideways (laterally) or
radially (ovality).

If no luck here, try relocating the pointer at the center of the tire tread
and rotating tire. Movement relative to the poiner tip means an irregular
tire.

Andrew Grebneff
165 Evans St, Dunedin, New Zealand
ph   64 (3) 473-8863
fax 64 (3) 479-7527
<andrew.grebneff@stonebow.otago.ac.nz>
www.goingplatinum.com/member/vw1
www.highyieldcrusaders.ws/ref.html?ref=vw
VW & Toyota vans, Toyota diesels and Macintoshes rule