Check brake disks for wear - AP42.10-P-4258-02RQ

10.5.10

Test sequence completely changed

Part no.	Designation	Quantity
A 197 001 77 99	Test film	As required

The wear on the brake disk may only be determined by evaluating the wear indicators (1) on the test film (2).

3 wear indicators each are located on the inner and outer friction surface (1).

The dimension and weight specifications on the brake disk bowl cannot be used for wear determination!

1. Detach test film (2) from carriers, place in the center on the wear indicators (1) and press on. Mark position of wear indicators (1) on test film (2).
2. Photograph all the test film (2) using a digital camera several times.

   Distance of approx. 10 cm, select macro function without flash.

3. Choose a representative photo of each wear indicator (1) on the computer monitor and zoom to an edge length of min. 3.5 cm.
4. Count off all squares, in which burnt surfaces (light points) are visible and note the number in the table.

   One square < 50 % burnt out counts as 1 2 square.

   One square ≥50 % burnt out counts as one 1 square.

   Fig 2: Identifying Position Of Wear Indicator On Test Film

   Courtesy of MERCEDES-BENZ USA
5. Add counted off squares.

   If the sum of the squares of all wear indicators (1) of one brake disk is > ≥96, then both brake disks and all brake pads of this axle must be replaced.

6. Detach all test film (2) and use dry cloths to wipe away any residue.
7. Archive photos.

Example A: 

17 squares < 50 % = 17 X 1/ 2 square = 8, 5 squares

8 squares ≥50 % = 8 X1 square = 8.0 squares 

16.5 squares

Example B: 

11 squares < 50 % = 11X 1/ 2 square = 5.5 squares

14 squares ≥50 % = 14 X1 square = 14, 0 squares 

19, 5 squares

Wear indicator	LF	RF	LR	RR
1
2
3
4
5
6
Sum
OK	Yes□ No□	Yes□ No□	Yes□ No□	Yes□ No□