This tech article will go over measuring your brake rotors to see if they require replacing. When checking brake rotor thickness, measure the rotor in about 10 different spots. Mark each spot to keep track of where you have measured. If the rotor does not meet minimum thickness then replace. Remember to always replace brake rotors in pairs. If your brake rotor passes thickness but you have a pulsation while using the brakes, replace the brake rotors. Also inspect the rotors for overheating, cracks and rust on the braking surface of the rotors.
If your brake rotors are close to the wear limit, I suggest replacing them. A lot of times it may seem they can be machined, but once you begin, enough material is removed to consider them no good.
Remember your car may have been serviced before and parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.
Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below.
|Brake Rotor minimum thickness per E53 model:||Front||Rear|
|3.0i, 4.4i||28.4mm (1,12 in)||10.4mm (0.41 in)|
|4.6i, 4.8i||34.4mm (1.35 in)||18.4mm (0.72 in)|
|Machining limit||0.8mm (0.03 in)||0.8mm (0,03 in)|
Most factory rotors and some aftermarket rotors will have a minimum thickness stamped (green arrow) on the rotor. This will be in the area of the hat or hub flange. Clean rust away from the rotor to uncover specs. There may also be a part number.
Lift the axle of vehicle you are measuring brake rotors on. See our tech article on jacking your vehicle. Using a micrometer, measure the brake rotor in at least 10 different places. I like to mark that place of measurement using a marker. Sometimes finding a rotor with thickness variations can help you find the source of a brake pulsation.
It is also a good idea to measure your brake pads. Replace the rotors when they are at or under 3 mm. The measurement gauge I am using in this photo is color coded to help identify how close to replacement my brake pads are. Measure both brake pads at each wheel. Some rotors tend to wear faster than others.