Well you're going at it right by eliminating one variable, that by your own admission, may have been a problem prior to the tire change and the new tire just exacerbated the problem. I doubt it's the tire, although I do remember a thread about a bad batch of Avons? I have one on the front and it's about 10 times better than the Metz and smooth as silk.
My guess is that the tire installation was done incorrectly. I have seen this a couple of times where the torque sequence on the "U-bolts" clamping the axle was incorrect and it reeked havoc with the front end until they were released and re-torqued correctly. So if your new triple tree bearings don't correct the problem, get the weight off the front tire and release and re-torque. Sounds crazy but I've seen it before?