At 60 miles per hour, an average size tire rotates 850 times per minute. At this speed, slight variations in balance, sidewall stiffness or roundness can cause the wheel to literally slam into the pavement 14 times a second. The ultra-sensitive road feel of today's vehicles gives drivers a hands-on detection of vibration, a warning of potential problems. Unchecked, excessive wheel vibration can result in expensive damages and unsafe driving conditions such as:

Wheels Out of Balance

Static wheel balancing uses a single weight plane and only addresses "up-and-down" imbalance. This is simply not adequate for today's vibration sensitive vehicles.

Dynamic wheel balancing uses two weight planes. This eliminates "up-and-down" and "side-to-side" imbalance. Dynamic, two plane wheel balance should always be requested, even on custom wheels when hidden weights are required.

Wheel Force Variation

A perfectly balanced tire can still vibrate due to Force Variation.

Wheel Force Variation is most frequently due to wheel runout or uneven tread or sidewall stiffness in the tire. Runout is when a tire or rim is out of round when rolling; frequent causes are a bent rim or uneven tire wear.

Uneven tread or sidewall stiffness can be found in new or worn tires. Tires by design are never uniformly flexible throughout nor are they perfectly round. And no two tires are exactly alike in these characteristics.

How Wheel Force Variation is Corrected

1. Match mounting a tire and rim by matching the high point or stiff spot in the tire with the lowest spot in the rim, can make the wheel "round when rolling."

2. In some cases a wheel is so out of round it should be replaced.

3. In some cases a tire with excessive Force Variation is defective.

Improper tire pressure and/or misalignment causes irregular tire wear which creates and amplifies imbalance, resulting in wheel vibration. Alignment can be adjusted and wheels serviced to reduce or stop the vibration. Ask your technician.

Steering and suspension components need periodic inspection. They can eventually wear out resulting in wheel vibration. Excessive wheel vibration from other causes can also shorten steering and suspension component life.

Other Hidden Causes of Wheel Vibration

• Wheel to axle mounting error
• Brake component wear or failure
• Drive train or engine component wear or failure
• Vehicle component characteristics

A knowledgeable technician with proper training and equipment can diagnose these problems. But, the only way to rule out all wheel-related vibration is with the Hunter GSP9700 Vibration Control System.