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Brake Rotor Specification Checking
 
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Pelican Technical Article:

Brake Rotor Specification Checking

Nick Czerula

Time:

1.5 hours

Tab:

$50

Talent:

**

Tools:

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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Comments and Suggestions:
Ken Comments: No, while the standard production 3 series moved to the E90, the M3 stayed with the E46 chassis for 2006. It seems that there was typically a year delay for new chassis to be "M'd", at least for the older models...

That's actually something that has bugged me on multiple BMW aftermarket web sites.

E46 M3
Overview
Production 2000–2006
85,744 built

For reference see:

https://en.wikipedia.org/wiki/BMW_M3#E46_M3

"The fourth generation BMW M3 was announced on the 2007 Geneva Motor Show Switzerland, 6–18 March 2007 with the BMW M3 concept."
July 18, 2017
  Followup from the Pelican Staff: Then look to E46 M3 brake info. - Nick at Pelican Parts  
Ken Comments: I just bought a 2006 E46 M3 ZCP with the two piece rotors. Is the minimum thickness for these rotors the same as the standard E46 M3?
July 17, 2017
  Followup from the Pelican Staff: Is it E46 or E90 chassis? Should be E90, see here: http://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E90/BRAKES-Brake_Rotor_Specification_Checking/BRAKES-Brake_Rotor_Specification_Checking.htm - Nick at Pelican Parts  

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Page last updated: Mon 7/24/2017 02:23:39 AM