Tire balancing
Despite advanced tire manufacturing processes and advanced rubber
compounds used today, some weight imbalance can still be evident in new
tires. Therefore they should be balanced with wheel weights to achieve
smooth rolling of the tire. An imbalanced tire expresses itself as a
wheel shimmy (rocking back and forth of the steering wheel while
driving, usually at a specific speed).To balance a tire, it must first be mounted in the proper rim and then inflated to the proper air pressure and a new valve stem installed. Next, the complete tire/wheel assembly is affixed to a machine that is designed to spin the tire and identify the location and severity of the imbalance. The tech must then affix the proper weight to the rim in the location designated by the machine. Finally, the wheel is spun again to ensure that the tire is properly balanced. A tire is balanced based on the mass of rubber present at the time of its first balance. As the tire rolls down the road, rubber wears off, causing the tire to become imbalanced again. For this reason, when tires are rotated on the vehicle every 5-6,000 miles or 6 months, they should be checked and rebalanced if necessary.