Brakes - New Disc Checking Tools

GROUP 34
Brakes



Bulletin Number
34 02 88 (1585)



Montvale, NJ
February 1988
Technical Dept.



SUBJECT:
Brake Discs Checking

MODELS:
All

Situation:
In order to allow faster and more accurate checking of brake discs, two new tools are being sent to all dealers via the Automatic Tool Shipment Program.

The first tool is a vernier caliper, BMW P/N 88 88 6 341 280. This brake disc caliper is designed to measure discs that have been grooved or that have a lip around the edge and do not allow measurement with an ordinary flat faced caliper. This caliper also has a floating scale feature which allows the measurement to be locked in place while the caliper is opened and removed from the disc.



The second tool is brake disc finish comparison gauge, BMW P/N 88 88 6 341 270. This tool is a section of brake disc showing acceptable wear on one side (YES), and excessive wear on the other (NO). It is used to perform comparative check of a used brake disc to see if the condition of the friction surface allows it to be re-used without machining.



Operation:





Tool # 341 280 Open the jaws of the caliper at least 10 mm wider than the thickness of the disc. Close the jaws to the work by pushing button "A", which will cause the stop "B" to pull the sliding scale to the correct reading. Lock the sliding scale in place by tightening lock knob "C". The jaws can now be opened to allow the caliper to be removed and read in the normal manner.






Tool # 341 270 Compare the surface of the brake disc on the car with the sample. If the disc is as smooth or smoother than the "YES" side of the tool, the disc does not have to be machined.



It can be re-used if, a) the thickness of the disc is greater than the machining limit stamped on the disc, and b) it is within tolerances for runout and thickness variation.

If the surface of the disc is rougher than the sample on the "YES" side of the tool then the disc must be machined or replaced.