Note: Before starting work, refer to the warning at the beginning of Section 4 concerning the dangers of asbestos dust.

Inspection
Note: If a disc requires renewal, BOTH discs on the same axle should be renewed at the same time (ie both front or both rear) to ensure even and consistent braking. New brake pads should also be fitted.

1 Remove the brake pads as described in Section 4 or 6 as applicable.

2 Inspect the disc friction surfaces for cracks or deep scoring (light grooving is normal and may be ignored). A cracked disc must be renewed; a scored disc can be reclaimed by machining provided that the thickness is not reduced below the specified minimum.

3 Check the disc run-out using a dial test indicator with its probe positioned near the outer edge of the disc. If the run-out exceeds the figures given in the Specifications, machining may be possible, otherwise disc renewal will be necessary.

4 Excessive disc thickness variation can also cause judder. Check this using a micrometer.

No actual thickness variation figures are provided by the manufacturer, but as a general guide, 0.010 mm should be considered a maximum.

Removal
5 On certain models, it may be necessary to remove the brake caliper with reference to Section 7 or 8 in order to allow sufficient clearance to remove the disc. Note that there is no need to disconnect the flexible hose from the caliper. Support the caliper with wire or string, taking care not to strain the hose.

6 To remove the disc, unscrew the two cross-head screws (where fitted) and withdraw the disc, tilting it as necessary to clear the hub and caliper if the caliper is still fitted.

Refitting
7 Refitting is a reversal of removal, but make sure that the disc-to-hub mating surfaces are clean and that the securing screws are tightened fully. If the caliper has been removed, coat the caliper mounting bolt threads with locking fluid on refitting. Refer to Section 4 or 6 when refitting the disc pads.