the worst case of wobble i've ever had, where it was unridable at 10mph when handsfree, was when, as an experiment, i switched wheels from 630 (27") to 559 (MTB). on the 630's the ride was dead solid at any speed.

on another bike, when loaded for touring with 559 wheels, it was very bad handsfree, starting at about 20mph. without any touring baggage it was fine. recently, i switched to 650c wheels and the wobble came back.

my experiences lead me to believe that front end weight, or rotating weight, and the flexibility of the frame, or lack of it, are significant factors. so i suppose some experimenting with different weight tires/forks may make some difference.

BTW, as you can see, my problems didn't have anything to do with bearings or loose spokes or out of true wheels.