1. Remove the wheel.
2. Remove the pads and push back the pistons
using the proper tool for this operation.
3. Dismantle the complete caliper from its
support, without disconnecting the brake fluid ducts. Do not leave the caliper
hanging from the flexible ducts. Suspend the caliper in some way (for instance,
on a hook).
4a. Dismantle only the used disc, if this has a
mounting flange inside the carrier.
4b. If the mounting flange is external to the
carrier then it will be necessary to first dismantle the hub and then the worn
5. Clean the new disc with an appropriate solvent
(for example, petrol or spirit). The anti-corrosion layer must be completely
removed. The disc must not be contaminated by oil or grease as these substances
could be passed on to the pads and so reduce their performance. Carefully clean
the surface of the disc that will come into contact with the hub.
6. Carefully clean the surface of the wheel hub
on which the disc will be installed. Eliminate rust and other deposits. Check
that the support surface is neither distorted nor damaged.
7. Check that play in the bearings does not
exceed the tolerance and that the ball bearings rotate freely within their
crown. If possible, adjust the bearing.
8. Fit the brake disc on the hub.
9. For discs with a mounting surface that is
external to the carrier, fit the wheel hub and adjust the wheel bearing.
10. Once the disc has been fitted, use a DTI
Gauge (fixed to the suspension bracket) to measure disc run out on a braking
surface at the point of its external diameter. At the end of one complete
rotation, run out should not exceed 0.10 mm. If it is greater, change the
position of the disc on the hub (provided that the mounting aperture allows
this), or fit the second disc from the pack. If the disc is held in place by one
bolt only, secure it to the wheel hub by two other bolts (using wheel studs plus
washers to compensate for the thickness of the wheel) in order to simulate
rotation conditions once the wheel has been fitted.
disc run out is a vitally important operation:
if there should be too much run out then in time, after a few thousand
kilometres, the disc may be subject to abnormal wear when travelling - and
outside of occasions when the brakes are applied (due to slight rubbing against
the pads) - and braking vibrations may occur.
11. When the maximum recommended run out for the
disc is exceeded then check run out for the bare hub. It should be borne in mind
that the value recorded for the hub will double when measured at the outer
diameter of the disc.
12. Fit the caliper to its support. A floating
caliper must move smoothly and regularly along its guides. The pistons must move
freely. Dust shields must be integral.
13. Fit the new pads - they must be free within
their seats. Fit the springs and any other parts included in the kit.
14. Before fitting the wheel make sure that the
rims are not distorted.
Balance the wheel/tyre unit correctly. Tighten bolts in the correct sequence and
observe the recommended torque.
15. Check that the elements comprising the
suspension are integral. Check that the shock absorbers function properly. The
suspension adjustment must correspond to the manufacturer's recommended values.
TESTING AND RUNNING IN
Once the discs and pads have been replaced, the mechanic should then carry out a
road test. He must ascertain that there are no brake vibrations or noises,
either while travelling or during braking. He must also check that the braking
action is both correct and efficient, even though the brakes are not yet run in.
It is the braking distance that is important. Never brake sharply during these
tests. The car user should be advised to observe an approximately 200 km
running-in period. During this period a short, smooth braking action should be
adopted so that the pads can align correctly to the disc surface. Too sharp or
heavy braking may not only cause the pads' friction material to overheat, but
also the disc itself. This would end up by compromising brake integrity and
performance. In particular, do not attempt to activate the ABS.