I've been trying to use an old set of Kirtland Tour Pack rear panniers on the front rack of my Trek 520. I immediately have severe front wheel wobble or shimmy. I've moved the weight around within the bag trying to get the heavier stuff down and to the inside. I've been carrying about 10 pounds in each bag. I've got Ortlieb Classic panniers on the rear. The Kirtland bags have a large outside pocket as well as a small outside pocket in the front.
I've concluded that the outside pockets create too much wind confusion which wobbles the wheel. Does that seem possible? I'm thinking that my only answer is to buy real front panniers.