We don’t always think of the tolerances required on vehicles but in this day and age with vehicles being faster and more powerful, tolerances play a key part in the comfort, reliability, and performance of the vehicle.
Explained in this article, Lateral Run-out (or simply run-out) is a measure of how much off-centre a brake rotor is as it spins around the hub. A vibration, or pulsing, in your brake pedal or steering wheel when your apply your brakes may indicate that your run-out is off tolerance. In this article, we will go over how to check it. Luckily it’s pretty simple and you only need one tool to do it: a dial indicator. Here are some best-sellers from Amazon.com.
Check Rotor Run-out in 9 Easy Steps
- Remove the wheel
- Reinstall the lug nuts/bolts to ensure the rotor is secured to the hub.
- Anchor the dial indicator to a fixed, non-moving base (usually on the steering knuckle).
- Position the dial indicator such that the needle is perpendicular to the rotor and is measuring about 10mm from the edge of the rotor.
- Lightly tap the dial indicator onto the rotor a couple of times to test the needle’s readings.
- Slowly rotate the rotor and find the point where the dial indicator is giving you the lowest reading on the rotor.
- Zero the dial indicator at this point.
- Continue to rotate the rotor to find the point where the dial indicator is giving you the HIGHEST reading.
- This reading is your run-out.
As a point of reference, consider that the maximum allowed run-out in most modern vehicles is around 0.05mm (2/1000 in).