How to Check Your Car’s Brake Rotor Runout

Brake rotor runout is a bad thing. If you have excessive runout, you will need to have an auto repair performed on your brakes. Runout is caused is by the rotor being able to wobble. Checking the runout is a quick and easy way to determine if you should replace the brake rotors. This step-by-step guide will walk you through each step of the process.

Directions

1

Gather Your Tools

The first thing that you need to do is to gather the tools you will need to check the rotor’s runout. For this maintenance, you will need a car jack, jack stand, parking brake block, screwdriver set, torque wrench, socket set, brake cleaning fluid, a rag, dry erase marker, dial indicator stand, and dial indicator. You will also likely want something to hold the hydraulic line while you service the brakes. A piece of wire or a bungee cord works great for this.

2

Jack up the Car

After gathering your materials, you are ready to begin the repair. Use your car jack and jack up the car. Once it is raised place a jack stand underneath to hold you car securely. If you are checking one of the front wheels, you wheel want to place a car break block behind the back wheels to keep the car from rolling.

3

Remove Tire

The next step is to remove the tire. Loosen each bolt, and then pull the nut off each one. After this, you should be able to remove the wheel. If the wheel is stuck on, it can be helpful to take a large stick or wooden block and strike the wheel with it. This will help jar the wheel, and can loosen any rust that has the wheel stuck to the bolts.

4

Remove Caliper

The caliper will be held to the brake rotor by a large bolt. You will want to remove this bolt. Then you will be able to slide the caliper off of the rotor. It is important that you do not allow the brake line to become disconnected from the caliper. A good tip is to hand it from the bottom of the car using the bungee cord.

5

Clean the Brake Disc

Use brake cleaning fluid and the rag to wipe off the brake disc. You want the surface to be free of dirt and grease.

6

Mark the Disc

Now you want to mark the disc at 45-degree intervals using the dry erase marker. There will be eight marks in total. To measure 45 degrees, you can place two marks across from each other. Then place a mark at each halfway point between them. Finally, mark each half way point again. Number the marks one through eight.

7

Check Runout

You are now prepared to check the rotor runout. Use the dial indicator and the dial indicator stand. You want the dial indicator to connect with the disk about a half inch from the rim. Turn the disc to number one, and then zero the dial indicator. Then, you will need to turn the disc to the number two mark. Record the value. Do this for the remaining six marks.

8

Measure Runout

The runout is the difference between the highest measurement that you recorded, and the lowest. You want the runout value to be less than 0.002 inches. You will need to replace the rotor if you record a higher runout reading.

9

Install Caliper

After checking the runout, you are ready to reassembly the brake and wheel assembly. You will need to reattach the caliper. Slide it back on the rotor, and then tighten the bolt to hold it in place. Make sure that you do not stretch out the brake line.

10

Attach Tire and Lower Car

The final step is to reattach the tire, and then lower the car. When you are tightening the nuts on the tire, make sure that you tighten them in a star pattern. You should perform at least two passes over each nut when tightening. After the wheel is attached, use the car jack to raise the car off the stand. Remove the stand, and then lower the car.

You can follow this procedure to check the brake rotor runout. This is a very basic car repair, and will indicate if you need to perform more extensive maintenance. If you can perform this procedure, then you will also be able to install new rotors if needed. The procedures for both are very similar.