Want to know how close your front disc brake rotors are to the limit? They’re pretty easy to measure.
Grab a measuring device – a set of digital calipers is convenient:
Sometimes there’s a lip on the edge of the rotor:
There is only a barely discernible lip here since the rotors are basically new, but if you have a more marked ridge a set of calipers with a slight indent like this is quite handy:
Put the calipers on the rotor:
These rotors have around 200km on them, and measure out to be 4mm precisely. How close is that to the limit?
Rather a long way – the limit is 3.5mm, as you can see from the inscription on the rotor itself.