3421947 Precision-turning both rear brake discs on both sides

IMPORTANT: Always precision-turn both sides of both brake discs on one axle.
Observe Max. machining dimension per friction ring side. See REAR BRAKE .
Minimum brake disc thickness (MIN TH), see REAR BRAKE .

Stationary brake disc lathe

IMPORTANT: Only BMW-approved brake disc lathes may be used!

In the case of stationary brake disc lathes, the BRAKE DISC MUST BE REMOVED .

Please refer to the lathe manufacturer's instruction manual for the exact procedure.

Fig 1: Identifying Stationary Brake Disc Lathe

Courtesy of BMW OF NORTH AMERICA, INC.

Mobile brake disc lathe

IMPORTANT: Only BMW-approved brake disc lathes may be used!

In the case of mobile brake disc lathes, the BRAKE CALIPER and the brake anchor plate must be removed.

The brake discs remain on the car.

Please refer to the lathe manufacturer's instruction manual for the exact procedure.

Fig 2: Identifying Mobile Brake Disc Lathe

Courtesy of BMW OF NORTH AMERICA, INC.

After fine-grinding the brake discs, measure the thickness difference. See REAR BRAKE inside the braking surfaces at 8 points with an external micrometer.

Fig 3: Measuring Brake Surface Thickness Using Micrometer

Courtesy of BMW OF NORTH AMERICA, INC.