'Am in the process of replacing rear brakes on my 2003 x-type, automatic 2.5L. The current thickness of the rear disc rotors is about 0.415" (10.54 mm). The current thickness measurements were made with a fine Swiss micrometer. The published discard thickness seems to be 0.400" (10.20 mm). Based on the current thicknesses, should I to replace the disc rotors at this time as well, or will these be good enough till the next brake job, even though the discs may end up being marginally below the 0.400" level by the time the next brake job comes up. The car only has 75,000 miles on it since it was purchased brand new in 2003; I'm the original owner. These are the original discs. The wear rate over the years calculates to about 0.0008" per 1K miles (0.020 mm per 1K miles). Based on this wear rate, my druthers are to keep the existing discs. Can someone please provide an opinion as to whether the discs should be replaced now as well. Thank you.

 

The current rotors are within spec; you should keep them. The designers certainly
considered this situation when they wrote the spec.

If the rotors are otherwise good, not warped, don't be in a rush to change them.
Any new ones that you get may not be as good. i.e. produced in countries with
questionable quality.

 

The min. thickness on a rotor is the 'acceptable for return to service' indication. The OEM calculates and builds in a 'wear allowance' factor when determining this dimension.

 

Thank you jagger and thank you Mickey for your prompt responses. Agreed with the idea that the designers surely must have built in a margin of safety into the wear factor with the thickness specs, and they assumed that owners would surely go past the discard measurement by the time they got to their next brake job. Yes, the rotors are in good shape; no groves, no braking pulsations experienced with the old brake pads. The disc surfaces feel nice, flat and smooth while passing over them with the tips of my fingers, even though they have the appearance of being passed over by 125 grit sandpaper. That's probably rubbing marks from the semimetallic pads. "Premium" grade pads are being installed. Thanks again for your kind responses.

 

Since the rear rotors are solid and don't wear as fast as the fronts, if they're still acceptable I would keep them till next inspection, don't replace what you don't have to.

 

Than you, Thang, for your response. I really appreciate it. As all of you guys suggested, the existing rotors were retained, and the brakes work great.