BMW X3 vehicles are equipped with disc brakes at each wheel. The front discs (or rotors) are larger vented for better cooling. The rear rotors are solid or vented, depending on the brake package and engine size. The parking brake is integrated into the rear rotor. To withstand the mechanical and thermal stresses of braking, brake rotors are required to be replaced if they are worn thinner than a certain minimum thickness. This minimum thickness is stamped on the edge of the rotor.
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 specifications, replace it. 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 for overheating, cracks and rust on the braking surface of the rotor.
|Brake rotor minimum thickness per X3 model||Front||Rear|
|X3 332x30 mm front rotor, 320x22 rear rotor||28.4 mm (1.11 in)||20.4 mm (0.80 in)|
|X3 325x25 mm front rotor, 320x22 rear rotor||23.4 mm (0.92 in)||20.4 mm (0.80 in)|
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. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.
Most factory rotors and some aftermarket rotors will have a minimum thickness stamped (red arrow) on the rotor. This will be in the area of the hat or hub flange. Clean the rust away from the rotor to uncover the specs. There may also be a part number. BMW X3 model front rotor shown.
It is also a good idea to measure your brake pad thickness (red arrow). Replace when they are at 3 mm (0.12 in.) or below. The measurement gauge I am using in this photo is color coded to help identify how close to replacement my brake pads are.
Lift the axle of the vehicle you are measuring brake rotors on. See our tech article on jacking your vehicle. Using a micrometer, measure the brake rotor (red arrow) 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. A flat jawed caliper (blue arrow) will not work unless it has point adapters, as the jaws usually hit the rotor ridge, not allowing an accurate measurement.