New Mst Problem maybe? Need advice!

Hello I have a set of 26-9.5-12 and 26-12-12 MST tires. I have been doing some research on here and I have noticed some people have had problems with a wobble. Well I have the same problem I think. I don't know where to start. I have put every combition on my quad to see where it is coming from. What I mean by that is putting my stocker fronts on with the mst's on the rear. Stockers on the rear and mst's on the front and just running MST's and just running stockers. I'm not sure if I should call it a wobble or shimmy in the front or rear. I felt a wobble in the bars no matter what combo was on other then having all stockers on. Then I just felt a very small shimmy when I was going above 40 mph. BUt the thing is going down one side of the road I feel a wobble starting at 33 mph but going down the same road later I felt no wobble up to 40 mph. What could cause the wobble the first time but not the second. Could the front and rear tires be bad? I just don't want to send something back that might be good. It just doesn't make sense to me. With my front stockers on and the rears with MST's I felt no wobble then I could go back down the same street and feel a wobble in the front. Thats why I don't know if the front and back are both bad or is it going to wobble a little bit because of the bigger lugs compared to stockers. Could all the tires be out of round or just the front or do you feel that everything is fine? Sorry for the long post. I just wanted to be really detailed. Thanks for any advice