I am looking to upgrade the Tektro calipers on my CAAD 10-5 to Shimano 105's. In looking online I find calipers with a 49mm drop but I don't know how that is measured. My current calipers measure about 49mm from the underside of the brake arm to the bottom of the flange where the pad mounts. Am I measuring in the correct place and do I need 49mm calipers? Thanks.