[Ariel Red Hunter]

Originally Posted by Weldangrind

It could one of a few different causes or the tolerance stack-up of a few issues. Off the top of my bald head:
Rims aren't true, front caliper dragging a bit, steering neck not set up properly, poor quality tires, steering neck isn't true to the frame (that's a long shot), either (or both) rims aren't centered on the axle, etc.
Before tearing anything apart, ride the bike slowly on a surface that will tell you what the tires are doing, like a bit of sand or water on the road; there should be only one tire track, not two. Then, put the bike on a stand and check both rims. Do they spin freely? Are they out of round? After those simple tests, you can begin to diagnose.

I had that problem once, years ago. Headstock bearings were too tight, and needed grease....ARH