What Is Meant By Radial Runout In Tires?

Radial runout in tires is a term describing the deviation of a tire’s roundness from a perfect circle. It measures the variations in tire diameter from the wheel midpoint to any point on the rim. This discrepancy impacts the wheel rotation, causing a ‘hop’ or ‘bounce’, and affects the vehicle’s performance and ride quality​​​​.

How to Measure Radial Runout?

To accurately measure radial runout, you need specific tools i.e. a dial indicator for measuring lateral movement, a magnetic base to stabilize the dial indicator, a wheel stand for tire rotation, and a wheel balancer.

The process involves parking the vehicle on a level surface, attaching the dial indicator to the wheel hub, positioning it against the tire tread, and rotating the tire by hand to measure lateral movement or runout. The maximum runout reading is noted, and the process is repeated for accuracy. The average of these readings is compared against the tire manufacturer’s specifications or industry standards to determine if the runout is within acceptable limits.

Effects of Radial Runout on Tires

Radial runout can lead to several issues. It tends to be self-propagating, meaning once it begins, it progressively worsens. The greater the discrepancy in radial runout, the more the wheel bounces up and down during rotation, causing vibrations noticeable inside the car. This bouncing leads to irregular tire wear and affects the vehicle’s overall performance.

Causes of radial runout include manufacturing defects, uneven tire wear due to improper alignment, or lack of maintenance​​​​.

How to Fix Radial Runout In Tires

Addressing radial runout involves a few steps:

  1. Begin by thoroughly inspecting the tire and wheel assembly to determine the presence and extent of radial runout.
  2. Carefully remove the tire from the wheel. This step requires proper tools and techniques to avoid damaging the tire or wheel.
  3. Apply lubrication to both the tire bead and wheel rim. This helps in achieving a better fit and reduces the chances of runout due to improper seating of the tire on the wheel.
  4. After lubrication, rotate it 180 degrees on the wheel. This rotation can help even out any discrepancies in the tire wall thickness or wheel rim that might be causing the runout.
  5. After repositioning the tire, inflate it to the recommended pressure. Ensure you seat the tire properly on the rim.
  6. Use a runout gauge or a dial indicator to recheck the radial runout. Make sure it is within the acceptable limits as specified by the tire manufacturer.

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