CCM wear: relevance of indicated maximum weight loss...

... or how to determine weight loss

My official Ferrari dealer told me I have to replace the brake discs of my FF and thus also the brake pads as they go together. The algorithm used by the car had indicated this. This would cost me around 20k euro. The car has done 95k kms. As I only drive long stretches and anticipate to the max, I always say to others I never brake. And indeed is ‘wear’ never the reason to replace discs on other cars I have (driven).

So I wanted to find out myself how the condition of my discs are. According to the workshop manual there are two other variables to check, besides the algorithm: thickness and the appearance (visual inspection). With the thickness the manual is in error BTW as they say it may decrease 0,5 mm without discriminating between front and rear discs (fronts may loose 1,7mm from 38 to 36,3mm; rears 0,5 from 32 to 31,5mm). Mine were 37,6 front; 31,8 rear, so not even on 50%. After 95k.

Visual inspection did not give reason for concern, with a few blemishes on one of the fronts. What was surprising however that the mounting area of the front discs had a somewhat different appearance. As if one had been replaced already when new (I bought the car second hand with 15k on the clock).

That left a fourth way of determining wear (not mentioned in the manual) and this made the whole exercise a bit odd. So I wonder if anyone can help me with solving the riddle. The rear discs may loose 70 grams each and the fronts 300 gram. This is clearly indicated on the discs which all have an individual weight to start with (also indicated). For instance, my fronts where 6634g and 6774g new and should be replaced at 6334g and 6474g the latest, respectively. Now all the discs measured actually heavier than new. From a few grams to 20 grams (calibrated scale). We took the disc with the biggest increase and started to clean it intensively (there was some brake dust in the holes drilled into the surface for instance). After drying etc. this had no significant effect on the weight.

So that leaves the question what the relevance is of the minimum weight indicated on the CCM discs. Or the other way around, how do I weigh the discs ‘correctly’ cq what have I done wrong? The only thing I can think of is that the inner steel part of the discs will corrode to some extent during the years, and FeO is heavier than Fe. But then, this happens to all discs on every car and brings me again to the relevance of indicating a maximum weight loss. Who?

 

Thank you for your reaction, but that was clear to me. By addressing Ferrari Chat I am trying to find out how to cope with the indicated minimum weight. Algorithm, thickness and visual inspection I do understand.

 

##Perhaps the "new" numbers refer to mass when replacement should occur rather than total mass when new?##
No, that is not the case. The higher mass indicated is when new. Then below you will find the text "MIN WEIGHT XXXXg" .
The thickness when new is not indicated (which I understand as it is always the same), but the disc says "MIN TH 1,43" = (36,3 min)" (front disc).
It would also not be in line with the thickness of all my discs. Thickness suggest less than 50% wear; the weights measured would suggest replace all discs 'immediately' when the higher mass indicated is applied. And I haven't been calculating but the max thickness and weight loss at the fronts seems to correspond with the max thickness and weight loss at the rear (300 gram loss of weight for 1,7mm loss of thickness at the front compared to 70 gram loss of weight for 0,5mm loss of thickness at the rear), knowing that the front discs have a larger diameter.

 

Very interesting. Thx. But I read the manual and to me it is totally unclear wat the device actually measures. It says wear, but it does not say anything about what the display indicates. In the pictures I see a value of 52,0, but what does that indicate? The manual gives no clue...
The data sheet says "0.0 to 100.0 CQ". So 52 indicates 52 CQ, but what is 'a CQ'?. It says Carboteq, but what is 1 Carboteq?
And indeed 9k $ is prohibitive....
Most importantly, it doesn't address my question how to cope with the wight data on the discs....