Rear Brake Disc Lateral Runout

Measuring the rear brake disc lateral runout

Includes: Measuring the brake disc thickness tolerance

1. Measurement precondition: No tilt play at the wheel.





2. Fit the adapter plate (special tool 9510/1) to the wheel hub. Tightening torque of the wheel bolts (fastening screws): 130 Nm (96 ftlb.).
3. Insert dial gauge holder, e.g. Ate order No. 03.9314 - 5500.3/01, into the brake caliper, align it and secure it by turning the clamping wing screw. If the brake disc cannot be turned freely, set the brake pads back a little. Do not damage the expanding spring when fitting the dial gauge holder.

Information
^ If necessary, provide the dial gauge holder with the Ate conversion set, order No. 03.9314 - 5510.3101 (longer clamping wing screw and, possibly, also a bracket for the dial gauge).





4. Secure the dial gauge with some preload. Position the measuring tip outside the perforation on the largest diameter of the braking surface.
5. Turn the brake disc and, when doing so, read off the lateral runout at the dial gauge. The permissible lateral runout of the installed brake disc is max. 0.06 mm.

Lateral runout of the removed brake disc:max. 0.03 mm.

Wheel hub lateral runout: max. 0.03 mm.

6. If the brake disc lateral runout exceeds 0.06 mm, remove the brake disc and check the wheel hub lateral runout. First mark the position with respect to the wheel hub.
7. Check the wheel hub lateral runout as described below: Measure 1 x outside (arrow) and 1 x inside (arrow) of the wheel bolt area (5-point measuring procedure) on the front face of the wheel hub. Fasten the dial gauge using a commercially available universal dial gauge holder.

Information
^ The universal dial gauge holder can also be used to check the brake disc lateral runout





8. Wheel hub lateral runout is too large: Replace the wheel hub. Wheel hub lateral runout OK: Clean the leveling and centering surfaces on the brake disc and wheel hub. Next, apply a thin coat of Optimoly TA to the centering surface on the wheel hub. Fasten brake disc on the wheel hub in a different position than before - radically offset with respect to the wheel hub. Repeat measurement with fitted adapter plate special tool 9510/1. If the lateral runout is still greater than 0.06 mm, replace the brake disc.

Information
^ If the brake disc lateral runout was reduced by radial offset of the brake disc with respect to the wheel hub, one M6 screw can be omitted if two M 6 countersunk screws were present.

Measuring the brake disc thickness tolerance

Measure the brake disc thickness within the braking surface at approx. 8 points by using the micrometer.

Thickness tolerance of the brake disc max. 0.02 mm (new condition: max. 0.01 mm).