34 21 947 Precision-turning both rear brake discs on both sides

Attention!

Always precision-turn both sides of both brake discs on one axle.

Maximum machining dimension per friction ring side is 0.8 mm!

Brake discs of M models (Compound brake discs) must not be machined!

Only one brake pad set may be used up on brake discs which have been lathe-turned to minimum thickness (MIN TH).

Mobile brake disc lathe:

Attention!

Only BMW-approved brake disc lathes may be used!

In the case of mobile brake disc lathes, the brake calipers and caliper carriers must be removed.

The brake discs remain on the vehicle.

Fig 1: Identifying Mobile Brake Disc Lathe

Courtesy of BMW OF NORTH AMERICA, INC.

After fine-grinding the brake discs, measure the THICKNESS DIFFERENCE inside the braking surfaces at 8 points with an external caliper gauge.

Fig 2: Checking Brake Disc Thickness Using Micrometer

Courtesy of BMW OF NORTH AMERICA, INC.