I was putting on snow tires last week, and i noticed that the driver's side tire would wobble slightly top to bottom when on a stand. What problem does that indicate?

I remember three tests, one with a wobble up-down, one with left-right, and the third in-out. I just can't remember which applies to which problem. Any ideas?

oh, and i finally found my oil leak. . .the oil pressure sender. after replacing my valve cover gasket and buying a new torque wrench, of course.