Brakes - Front Brake Shudder/Vibration
No: 70/08/04/NASFGN: LN206
Ref:
Issue: 1
Date: 19 November 2004
Front Brake Disc Vibration Resolution
AFFECTED VEHICLE RANGE:
Freelander (LN) All
SITUATION:
BRAKE PULSATION OR SHUDDER
A customer may report a concern of, or a recurrence of, vibration/shudder while braking. An earlier replacement of brake discs and brake pads for a similar complaint may have been performed. Vibration/shudder while braking can be caused by low levels of disc thickness variation (DIV) around the contact area of the brake disc. DIV can be generated even with moderate levels of brake disc run-out. Highway or freeway driving with slightly out of tolerance disc installation angles can result in the brake pads rubbing on the high areas of the rotating brake disc. This friction can cause disc wear (DIV) even when the brakes are not applied. Slight variation of the brake disc installation angle may be caused by contamination between the brake disc mounting surface and the drive flange, or a combination of drive flange run-out and brake disc run-out.
RESOLUTION:
FOLLOW PROPER BRAKE DISC INSTALLATION PROCEDURES
It is essential to measure the disc run-out for diagnosis of the concern and when new discs are installed to prevent problem recurrence. Should a customer express concern regarding the shudder symptoms, perform a disc run-out measurement and follow the procedure detailed in this bulletin to ensure that the risk of re-occurrence is minimized.
PARTS INFORMATION:
DDW WARRANTY CLAIMS:
DDW requires the use of causal part numbers. Labor only claims must show the causal part number with a quantity of zero.
Normal warranty policy and procedures apply.
Material allowance is included in labor operation.
REPAIR PROCEDURE
REPLACE BRAKE DISCS
NOTE:
Disc installation angle (Figure 1) can result in brake pad contact wear that results in a shudder or pulsation when stopping. A disc run-out measurement (Figure 2) will provide diagnosis of this concern. Each side of the vehicle will require the same procedure to be performed for an effective repair.
1. Raise the vehicle.
NOTE:
It is not necessary to renew brake pads when completing this procedure unless the lining minimum thickness is below specified tolerance of 3 mm (0.118").
NOTE:
GTR lookup sequence is as follows:
GTR Home > NAS > Service Information/ LN Freelanderl2OO5 > Workshop Manuals > Service Procedures > Bookmark "Brakes 70-1" > TOC "Repairs/Disc-front" link
2. Refer to GTR Workshop Manual section 70.12.10 and remove the front disc.
CAUTION:
The inside of the disc mounting hub and the surface of the drive flange must be thoroughly clean before installing the replacement disc.
3. Clean mating surfaces and install the replacement disc to the drive flange.
4. Install screws and tighten to 5 Nm (3.5 lbf.ft).
5. Measure the run-out of the discs as follows:
^ Mount a Dial Test Indicator (DTI) to LRI-99-503, and secure to inboard side of hub using caliper assembly upper bolt hole.
^ Position DTI probe 5 mm (3/16 in) inward from outer edge of the disc.
^ Fit road wheel and tighten nuts to 115 Nm (85 lbf.ft).
^ Zero DTI and rotate road wheel one complete revolution to measure that disc run-out does not exceed 0.05 mm. (0.002 in)
NOTE:
GTR lookup sequence is as follows:
GTR Home > NAS > Service Information/ LN Freelander/2005 > Workshop Manuals > Service Procedures > Bookmark "Front Suspension 60-1" > TOC "Front Suspension/Repairs/Bearing - hub" link
6. If disc run-out exceeds limits, perform the following:
^ Refer to GTR Workshop Manual section 60.25.14 and install a new drive flange and bearing.
^ Install brake disc.
Measure disc run-out following the procedure in step 5.
7. When run-out is within limits, remove road wheel.
8. Remove DTI and LRI-99-503.
CAUTION:
It is vital to any brake disc installation procedure that the mating surfaces are clean between the drive flange and the disc
9. Clean mating faces of caliper and hub.
10. Position caliper to brake disc.
11. Install bolts and tighten to 100 Nm (74 lbf.ft).
12. Install road wheel(s) and tighten nuts to 115 Nm (85 lbf.ft).
13. Depress brake pedal several times to set brake pads.