BigSwede; When you take your "bad wheel" in to get balanced make sure you have them perform a "road force" balance or test for "force variation" if they don't have the machine needed to test for it at sears, then call around and find one that does. It should only cost $8-$12 per wheel. Take in the wheel and have them "match mount" the wheel to the rim and re balance. If your wheel "hops" then it is likely out-of-round tire or rim and could be compensated if mounted properly and then balanced. Again if sears can only do a "static and/or Dynamic" balance you'll never get rid of the vibe.
-Jared