Note. catalog numbers of the brake disc and related parts see here.
Removing
Loosen the wheel bolts, put stops under the rear wheels «shoes». Engage the handbrake. Raise the front of the car with a jack, place it on secure stands, remove the wheel.
If work is being done on a lift: place the vehicle on a two-post lift, apply the parking brake and switch off the ignition. Remove front wheel. Raise the vehicle to a height convenient for work.
Clean Front Brake Parts (metal brush).
Unscrew and remove the two bolts securing the front brake guide to the steering knuckle (interchangeable head 18, extension and collar) (see details. Removing the brake caliper),
Remove front brake (caliper) assembly and hang it from the suspension spring. The brake hose does not need to be disconnected, but make sure that it is not overstretched or kinked.
Figure 11-1 - Removing the brake disc: 1 - front brake mechanism; 2 - front brake disc; 3 - brake disc mounting screws
Loosen and remove two screws 3, Figure 11-1, fastening the brake disc to the front wheel hub (replaceable nozzle Torx T40, extension, ratchet wrench).
To keep the disc from turning, you can screw the wheel bolt into the threaded hole of the hub and insert a mounting blade between the bolt and the hub shoulder.
... and remove the brake disc.
Checking the technical condition
See Full check of brake discs.
Attention. Brake discs cannot be sanded. In case of significant wear or deep scratches, the discs must be replaced.
Attention. When replacing a brake disc on one side, be sure to replace the brake disc on the opposite side.
Attention. When replacing brake discs, be sure to replace the brake pads.
Brake disc parameters
The marking indicating the minimum allowable thickness is indicated on the brake disc itself.
In this case, it is 19.8 mm.
Parameter | R90 | F90 | |
Brake disc diameter, mm | 259 | 260 | 260 |
Nominal thickness of the brake disc, mm | 20,6 | 22 | 22 |
Minimum brake disc thickness, mm | 17,7 | 19,8 | 19,8 |
Installation
Install the brake disc and secure it to the hub with two screws. Screw tightening torque 14 Nm (1.4 kgf·m).
Attention. After removal, the bolts of the guide to the steering knuckle must be replaced, since the fixation of the bolts is carried out with an adhesive composition applied to the threaded surface of the bolts. Bolts must not be reused.
Install the front brake assembly on the steering knuckle and fix it with new fastening bolts, first apply to the threaded surface of the bolts "High strength locking compound" in the amount of 1 g for each bolt. Bolt tightening torque 105 Nm (10.5 kgf·m) (interchangeable head 18, extension, knob, torque wrench, "High strength locking compound" spare part number 77 11 230 112).
Install the front wheel.
Press the brake pedal 2-3 times, check and, if necessary, top up the level of brake fluid in the reservoir of the hydraulic brake drive.
Check the efficiency of the service brake system.
Addition
Brake discs are a separate and important topic. The most dangerous are disks that have already exhausted their resource, so it is desirable to control their thickness at each thematic maintenance. What threatens exorbitant production? Cracks, for example, and, as a result, a jammed wheel at the most inopportune moment. In the case of non-ventilated discs, they can generally be brought to an absurd level of wear - when the pad falls into the gap between the caliper and the disc, the pressure drops in the system, and the brakes as a whole fail with it, and such cases also happen. So it is vital to check the thickness of the disk from time to time.
Now for a problem like «beat» disk. Of course, it is better to buy proven products, preferably with a certificate from TUV, otherwise the disk can start beating right from the first day of operation. But it also happens differently when a branded product eventually begins to annoy with vibrations. What's the matter? In a temperature difference, for example, I drove for a long time at a good pace, with acceleration and deceleration, and then suddenly drove through a deep puddle. There are many opinions on the topic of regrooving brake discs, however, based on experience and science, we can say that if it helps, it will be for a very short time. In the event of a significant temperature difference during operation, the disc «will lead» - it will change its structure in accordance with the well-known iron-carbon diagram, and not completely, but in places. So grind - do not grind, it will continue to lead. By the way, the world leader in the production of brake systems, the BREMBO company, agrees with this widespread opinion, and it knows a lot about extreme braking.
A lot has already been written about components for brake systems, including consumables - discs and pads, but it would be useful to recall a number of key points about where, how and what spare parts are better to buy. Naturally, it’s ridiculous to overpay 30-50, or even 100% for a cardboard box with the automaker’s logo, all the more so they don’t produce brake systems themselves, they use third-party services: BMW, for example, usually prefers Jurid, Mercedes-Benz - Textar, and so on.. You can purchase consumables directly from the catalogs of the manufacturers themselves - suppliers to the conveyor, if you are such a perfectionist, but usually it's easier to choose a certified product of the proper quality. I would like to remind you that it is better to purchase spare parts in well-tested places, since even the manufacturers themselves admit that in Russia the amount of counterfeit goods is off scale, and from the point of view of appearance, it looks perfect. However, this problem is not new and is not limited to Russia alone.