I posted a while back about hubcentric rings (NOT SPACERS), because I didn't get any 2 yrs ago when I bought the wheels. I still havn't been able to make them, but I noticed on the highway that the steering wheel would shake pretty bad for a while, then dissappear, then come back, then dissappear. you could almost set a clock to it (frequency dependent on speed of car).

could it just be off balance wheels? or could it be no hubcentric rings? what else could it be?

wheels might be unbalanced, maybe uneven wear of the tires

if it hit a pot hole hard enough u may have bent the belts in the tires. just something else to think about