Stuart,
After looking through my 6800 manual again I came across a little diagram for checking pad wear. Think the 3600 should be the same. Right at the bottom of the brake pedal, there is a wear limit mark that you should be able to see when brake is fully depressed. The bottom of the brake pedal kind've points to it. There is an adjuster too, what we were talking about before, turn the butterfly screw to line up the fixed washer with a mark, if that makes any sense.
Rattosh51
YT6800