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Front brake disc's for W109

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The new thickness of vented rotors is 19mm. 
The refinishing limit is 18mm.
The war limit is 17.80mm

So we only have 2.2mm of allowable wear.....that seems like very little. 

Ryan, The rotors from Mercedes are, or used to be, forged in house and heat treated.  I know they're still heat treated, but I don't know if they're still made in house.  The part number, 109-420-00-05, now has a "64" at the end of it....which usually means the part is sourced and/or made elsewhere.  So your guess is as good as mine. 

By the time you have the FEBI ones heat treated where will you be on price?  I imagine that may be a factor, too. 

s class:
Hi Aaron,

Thanks for that help and information.  I was under the impression from my workshop manual that 18mm was the min allowed, but I think thats the limit for machining as you say.  I have seen a new disc, and it's stamped "min thick 17.8".

The discs have been refinished apparently not too many miles ago, and measure up at 18.1 to 18.2mm.  No visible ridges or lips.  Its tough to say if inner and outer surfaces have lost equal material though.  Given that this car is not going to do much mileage, an option may be just to leave them be as theres 0.3mm left - I guess that would be customers choice. 

Any comments?

BTW heat treatment would be ~ $75 for a pair.

You haven't said what mileage or year the car is, but assuming it's last of off the line, so 1973, my super unscientific calculations suggest that at current mileage:

1.8mm of wear in 48 years => 0.3mm left / (0.0375mm wear / year) => 8 years of life left.

Say five to account for the unexpected.

Well, Lucas brings up valid point(s), but we also don't know if the rotors have ever been replaced in the past.  So true mileage is definitely a factor.  However, my view is that if there is .3mm left, the owner rarely drives it, and there is no warpage, then leave them on the car until they really need replaced.  In the 5-8 years that Lucas has accounted for regarding the time left, that'll give you and/or the customer plenty of time to buy the good rotors from Mercedes.  And you'd better do that sooner rather than later.  Just like with the early or late W116 rotors (I can't remember which) they will likely become no longer available very soon....with no plans of ever offering them again.  If they do offer them again they'll be double the price they are now.  Just be sure to use genuine Mercedes pads to get maximum life out of the rotors.  The Mercedes pads are very soft and easy on the rotors......and they're cheap!  :)


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