On the first day of my recent U.P. tour with my new Trek 520, I was shocked to find that my front wheel was shimmying all over the place when fully loaded, including front panniers. Riding at a comfortable pace, I couldn't stop my front wheel from moving back and forth like it had the DTs. I was very surprised at this, because I had heard from multiple posters on this site that a Trek 520 actually rides more smoothly when fully loaded than otherwise. Also, prior to the tour, I had loaded up the front panniers (with lighter material than I ended up with on the road) and experienced no problems during test rides. I was able to reduce the shimmy the first day by making some weight adjustments, and that night I rearranged my load completely so that much less weight was in the front. I also tightened up all the compression straps on the front panniers. That seemed to fix the problem. No front-wheel boogy for the rest of the tour, but my initial surprise and disappointment remained. Anyone else experience this?
BTW I have big-ish Trek panniers on a Tubus Duo front rack. The rack is rated for 33 pounds (16.5 pounds each side), and before my weight readjustment I had probably close to that in the front panniers.