Understanding Wheel Runout Tolerances
Every wheel has runout — the question is how much is acceptable and how much causes vibration. Here are the tolerances, how to measure, and when to fix.
Understanding Wheel Runout Tolerances
Wheel runout is how much a wheel deviates from perfectly round or perfectly flat as it spins. Every wheel has some runout — the question is how much is acceptable, and how much causes problems.
Two Types of Runout
Radial Runout
The wheel is not perfectly round — the radius varies around the circumference. The wheel moves up and down as it spins. Measured at the tire bead seat with a dial indicator.
Lateral Runout
The wheel is not perfectly flat — it wobbles side-to-side as it spins. Measured at the sidewall or bead seat with a dial indicator.
Both cause vibration: radial runout causes up-and-down; lateral runout causes side-to-side shimmy.
What Causes Runout
Manufacturing Tolerance
Every wheel has manufacturing tolerance — the wheel is never perfectly true from the factory. Quality wheels have tighter tolerances; cheap wheels may have 0.010+ inch of runout.
Impact Damage
Hitting a pothole or curb bends the wheel. A bent wheel has excessive runout at the impact location. Steel wheels bend; alloy wheels bend and can crack.
Heat Damage
Track use or hard braking can heat the wheel enough to distort it. This is rare on street wheels but common on track wheels without proper cooling.
Acceptable Tolerances
Radial Runout
- 0.002 inch or less — excellent, factory-spec for premium wheels
- 0.003-0.005 inch — acceptable for street use
- 0.005-0.010 inch — marginal; may cause vibration at highway speeds
- Over 0.010 inch — excessive; the wheel should be repaired or replaced
Lateral Runout
- 0.002 inch or less — excellent
- 0.003-0.005 inch — acceptable
- 0.005-0.010 inch — marginal; may cause steering shimmy
- Over 0.010 inch — excessive
How to Measure
- Mount the wheel on the car (or a balancer with a shaft the wheel bolts to).
- Mount a dial indicator with the tip on the bead seat (where the tire sits).
- Rotate the wheel one full revolution and record the total indicator reading — the difference between the highest and lowest points.
- Measure radial runout with the indicator pointing at the center; lateral runout with the indicator pointing at the side.
- Repeat at 3-4 positions around the wheel to find the maximum.
The Match-Mounting Solution
If a wheel has runout and a tire has a stiff spot, you can reduce the combined vibration by match-mounting — positioning the tire's stiff spot opposite the wheel's high spot.
A road force balancer does this automatically. Without one, you can find the wheel's high spot (max radial runout), mark it, and ask the tire shop to position the tire's heavy spot (or the dot on the sidewall) at that position.
When Runout Is a Problem
Runout becomes a problem when it causes vibration you can feel:
- High-speed vibration (60+ mph) that does not change with acceleration or braking is typically wheel-related.
- Vibration that changes with speed is often balance-related.
- Vibration under braking is often rotor or hub-related.
If you have a vibration and the wheels are balanced, measure runout. A wheel with 0.008+ inch of runout will vibrate no matter how carefully it is balanced.
Fixing Runout
Steel Wheels
Steel wheels can be straightened — a hydraulic press bends the wheel back to true. This is common and safe for moderate bends.
Alloy Wheels
Alloy wheels can be straightened by specialty shops, but the process involves heating the aluminum, which weakens it. Straightened alloy wheels should not be used on track or at high speeds. If an alloy wheel is cracked in addition to being bent, it should be replaced.
The Safe Choice
If a wheel has excessive runout and is alloy, the safest fix is replacement. The cost of a new wheel is less than the cost of a wheel failure at speed.
The Takeaway
Every wheel has runout — the question is how much. Measure it, understand the tolerances, and match-mount when possible. If runout is excessive, steel wheels can be straightened; alloy wheels should be replaced. A balanced wheel with excessive runout will still vibrate — because the problem is not weight, it is shape.