Cupping tires only happens when the tire is able to "wiggle" (cross
movement) sideways while turning over (around) in a straight line. You have
to find the cause for the "wiggle" in order to end the cupping. Thus tire
balance is just a important as an alignment, but again most of the time I
had to deal with cupping it was a cause of the shocks and or ball joints
(worn drag line on some vehicles). Anything that allows for the side to side
(cross) movement will cause cupping.