Turning brake-discs on the vehicle
For a while, the front brake-discs for middle-class cars, were quite reasonably priced, however, since that internal cooling is pretty universal, this is no longer so. Indeed. we don't intend to use the financial argument in
favour of grinding the car's brake-discs because we have something much better.
Basically, we do agree, that a brake-disc must be able to last for two sets of brake-pads. However, the workshop doesn't decide this, rather the manufacturer generally stipulates, when they are to be turned and how many
tenths may be turned off. The remaining thickness is of course, the deciding factor.
Indeed, one thing must be made clear: If changing only the brake-pads, then the disc should have a very smooth surface. And who is in a position to judge this? If this is not the case, the vehicle will more than likely, only be
braking on a part of the surface for quite a while. So, does that mean we should replace the discs with every brake-pad change?
No, assuming the disc is not worn down too far, that's not necessary. Since, as you may know, every system has a certain amount of inaccuracy, e.g., the brake-disc may not be perfectly plane to the hub. This is precisely
what the method shown here will remedy, this by the way, would not be the case if the disc was simply replaced. Of course, the condition is, that the brake-disc always remains exactly in this position and is always
mounted in the same place.
The video above is worth watching, you'll see that there is also a gauge. This should be mounted as far to the outside as possible (of course, still on the braking surface), now turn the wheel. You would be surprised to see
what happens with some vehicles. Another advantage of this method: The disc must not be dismantled to laboriously clean the contact surface. 09/14
Customary repair ...
1. Detailed customer questioning (if possible).
2. Examination on the braking test-bench.
3. Possible suspension damage?
4. Putting the electro-mechanical brake into the service-mode.
5. Possibly following all the points on the checklist.
6. Dismantling the brake-calliper and the brake-pads.
7. Securing the calliper with no tensile force from the brake-line.
8. Securing the disc with spacer-tubes and fastening it with wheel bolts.
9. Taking the thickness of the disc (without the edge) into consideration.
10. Determining the axial runout (both sides when internally cooled).
11. Measuring the thickness of the disc on at least 8 different points.
12. Checking the state of e.g., the brake lines and tubing.
13. Cleaning the contact surface of the disc.
14. Checking the axial runout (see above).
15. Repeating the measuring with the newly mounted disc.
16. Mounting of the brake support plates (manufacturer's data).
17. Greasing of the sliding surfaces (no copper-paste).
18. Pressing the front piston back, without tilting it.
19. Winding the rear piston back because of the hand-brake.
20. Finally, paying attention to any possible prescribed rotational positions.
21. Checking the state and the position of the dust-gaiters.
22. Applying the special paste to the rear side of the pads.
23. Reassembling, repeating the braking operation several times, checking the function.
24. Complying with the running-in requirements.