From my Haynes manual 42027 for more recent CR-V 2012 - 2016 and Civics 2012 - 2015, page 1 - 2 the minimum pad thickness is 1/8 inch (3 mm), and the minimum shoe thickness ( parking brake ) is 1/16 inch (1.5 mm). Apparently parking brake shoes are not very thick when new and do not need to be very thick when used because in general they only hold, and are seldom used to slow a moving vehicle.