Bit out of my depth here and could do with some help. Firstly could someone explain to me the difference between the disc and the rotor - what is what? Secondly see the attached picture of the readings. What are 2,3,4,5 actually telling me? Is 4 and 5 the carbon ceramic disc wear? 2 and 3 are confusing me - what's the rotor and what does the reading mean? Finally, is it possible to get a pad reading with the SD3 or SDX? Thanks Image Unavailable, Please Login
Rotor and disc are the same thing. The disc is mounted to a hat and the disc/hat combo is typically referred as the entire rotor assembly. It is my understanding that the SD3 readings for CCM are based on calculations, not actual measurements. I wouldn't put much into their meaning. The only way to determine the status of the CCM rotors is by a direct inspection and weighing the actual rotor. You are looking for cracks, pits, chunking, glazing, fiber loss, etc. Each CCM rotor is weighed when new and that weight is stamped on the hat. It will also have a stamped minimum weight. Unless you track the car, you are very unlikely to wear out CCM rotors in the street lifetime of the car unless one becomes damaged.
As above, the ECU "calculates" wear according to an algorithm based on braking intensity. The Rotor Wear numbers are the result of these calculations. The top number is the threshold for when the discs are worn out. The bottom two numbers are simply the second/third numbers divided by the top number (as expressed as a percentage). In short, what this is telling you is that this car hasn't seen much braking since the parameters were last reset - you'd hope that coincided with a rotor change!
Ah right, now I understand it. Thanks for that. So last question, is it possible to get a pad wear reading from the SD3 does anyone know, or is it disc only?
Disc only from SD3. If the pads are worn extensively, there is a pad wear sensor that will give you a warning light. Never let the pads get down to this level, however. It is recommended to change the pads when they are at 50% pad thickness (new 10mm so change when get to 5-6 mm thick). Rivets hold the pad material in place and begin to come thru the pad material at approximately 5 mm of thickness. They are brass rivets, but can create temperature differences across the CCM rotors and cause grooving or damage the $$$$$ rotors.
Thanks Teachdocs, read a lot of your posts about changing pads at 50%, they've been very helpful. You'd be surprised how few mechanics are aware of this. I shall be changing my pads asap!
