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Brake Rotor Specification Checking
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Pelican Technical Article:

Brake Rotor Specification Checking

Nick Czerula


1.5 hours






Micrometer, jack and jack stands

Applicable Models:

BMW E46 3-Series (1999-06)

Parts Required:

Brake rotors

Hot Tip:

Measure brakes in multiple places

Performance Gain:

Break performance restored

Complementary Modification:

Replace brake pads
BMW E46 vehicles are equipped with disc brakes at each wheel. The front discs (or rotors) are larger and usually vented for better cooling. The rear rotors are integrated with the parking brake drums. 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 the minimum thickness, replace. Remember to always replace brake rotors in pairs. If your brake rotor passes thickness but you have a pulsation while braking, replace the brake rotors. Also inspect the rotors for overheating, cracks and rust on the braking surface.

Most factory rotors and some aftermarket rotors will have a minimum thickness stamped 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.

Lift the axle of the vehicle you are measuring the brake rotors on. See our tech article on jacking up your vehicle.

Remove the wheels.

  Front Rear
 Brake rotor minimum thickness E46 20.4mm (0.80 in) 17.4mm (0.68 in)
 Brake rotor minimum thickness E46 M3 26.4mm (1.04 in) 18.4mm (0.73 in)

Using a micrometer, measure brake rotor in at least 10 different places.
Figure 1

Using a micrometer, measure brake rotor in at least 10 different places. I like to mark that place with measurement using a marker.

It is also a good idea to measure your brake pads.
Figure 2

It is also a good idea to measure your brake pads. Replace when they are at or under 3 mm.

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Page last updated: Sat 10/22/2016 02:19:52 AM