A correctly balanced wheel can rotate freely around its horizontal axis and is able to stop in every position. If there is a static imbalance, the spot on the wheel with the greatest mass is acted upon by gravity to deflect the wheel downward.
Static imbalance always occurs in the center of the wheel and causes it to bounce while driving. The static imbalance can be compensated by applying wheel balance weights on the opposite side of the occurred imbalance:
In addition to static unbalance, there is also dynamic unbalance.