Checking brake disc lateral runout

1. Measuring requirements: No tilt play present at wheel. If required, adjust wheel bearing clearance of front wheels.

2. Fit adapter plate (Special Tool 9510/1) to wheel hub. Tightening torque of wheel nuts (mounting nuts): 130 Nm.

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3. Engage dial gauge holder, e.g. Ate Part No. 03.9314-5500.3/01, into brake caliper, determine center position and fit by turning the wing screw.

Notes

If required, fit dial gauge holder with Ate conversion kit, Part No. 03.9314-5510.3/01 (longer wing screw and bracket for dial gauge if required).

Four-piston fixed caliper brake: Make sure the spreader spring locating lug at the mounting plate of the fixed caliper is not damaged when the dial gauge holder is fitted in place. Floating-caliper brake: To fit the dial gauge holder, the brake pads must be removed.

4. Fit dial gauge with a slight preload. Place measuring pointer on maximum diameter of braking surface.

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5. Rotate brake disc and read off runout on dial gauge.

Max. permissible runout of fitted brake disc max. 0.1 mm.

Note

The floating frame of the floating-caliper brake may touch the brake disc after the brake pads have been removed. When rotating the disc, push back the floating frame if required.

Runout of removed brake disc : max. 0.05 mm.

6. If the brake disc runout exceeds 0.1 mm, remove the brake disc and check runout of the wheel hub. Mark position of disc with regard to wheel hub.

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Checking brake disc lateral runout

Printed in Germany - XXV, 1992

7. Check wheel hub runout as follows: Measure once outside (arrow) and once inside wheel stud area of hube face. Lift off dial gauge carefully in cutout area of wheel hub.

To fit the dial gauge, use either a magnetic universal dial gauge holder, e.g. as supplied by SNAP-ON (Order No. PMF 137), or a dial gauge holder (VW 387).

Notes

Make sure the brake hoses and brake lines are not damaged when the brake caliper is removed and installed.

The above SNAP-ON order no. PMF 137 is valid for a complete dial gauge kit since the individual dial gauge holder is not available separately.

The dial gauge kit may also be used to check the brake disc lateral runout.

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8. Excessive wheel hub runout:

Replace wheel hub. Wheel hub runout o.k.:

Cleaning level and centering surfaces of brake disc and wheel hub. Then coat centering surface of wheel hub with a thin coat of Optimoly TA.

Fit brake disc to wheel hub in another position, offset radially with regard to wheel hub. Repeat measurements with fitted adapter plate - Special Tool 9510/1. If the lateral runout is still in excess of 0.1 mm, the brake disc must be replaced.

Note

If the brake disc runout has been reduced by offsetting the brake disc with regard to the wheel hub, one 6 mm countersunk screw may be omitted if two 6 mm countersunk screws had been fitted.

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