Proper tire and wheel assembly balancing are critically important from a vehicle safety standpoint. An out-of-balance tire and wheel assembly can cause vibrations that affect ride and handling, shorten the life of tires, bearings, shock absorbers and other suspension components, and drastically increase or create irregular treadwear.

Types of Imbalance

There are two types of imbalance caused by heavy or light spots:

• Static imbalance occurs when there is a heavy or light spot in the tire, causing it to roll unevenly in an up-and-down movement.
• Dynamic imbalance occurs when there is unequal weight on both sides of the tire/wheel assembly centerline, causing a side-to-side movement.

Run-Out

Excessive Run-out, or an out of Round tire and wheel assembly is often caused by improper bead seating on the rim. It may also be caused by not match-mounting the Tire and wheel assembly. A small amount of non-uniformity may not cause a vibration, a larger amount will cause vibration and irregular tire wear.

Radial Run-Out

An out-of-round situation where vibrations are produced as the wheel spindle moves up and down.

Lateral Run-Out

A less-common, side-to-side or wobbling movement of the tire and wheel. Sensitivity of a vehicle to vibration from radial run-out is four to eight times that of wobble caused from lateral run-out.

Sources of Imbalance

Sources of imbalance can be traced to heavy or light spots in the tire, radial and lateral run-out variations within the wheel (such as thickness and welds), and rotor and axle imbalances.

Correcting Non-Uniformity

Correcting Imbalance

Heavy or light spot balancing is corrected either statically or dynamically, depending on the type of imbalance.

• Static Balance is achieved with a static "bubble" balancer but does not correct for dynamic imbalance.
• Dynamic Balance is achieved with a dynamic "spin" balancer where the tire/wheel assembly is balanced both statically and dynamically.
  

Correcting Run-Out

Excessive run-out is frequently caused by damaged or poorly manufactured wheels Using a runout gauge, confirm the quality of the wheel by measuring the radial and lateral runout of the run flange. If the wheel does not exhibit excessive runout:

• Address radial runout by dismounting the tire, re-lubricating the tire and wheel, rotating the tire 180 degrees on the wheel and re-inflating.
• Address lateral runout by dismounting the tire, re-lubricating the tire and wheel and re-inflating