JRitt@essex

The backing plate thickness rule of thumb is a good one to follow. That is typically about 5mm. As others have mentioned, you need to watch them closely as they get thinner. They lose some thermal mass vs. when they are thicker and new, and they will burn more quickly the thinner they get. Also, make sure you always check the inner and outer pads in your calipers! The inners sometimes burn faster than the outers, so just peeking through your wheel spokes to asses the remaining life doesn't cut it! I've seen customers trash their discs when the steel backing plate digs into the the relatively soft iron disc ring.