from sheldon brown "The effective length of the arms of a caliper brake. This is measured from the centerline of the center bolt diagonally down to the middle of the brake shoe. Reach is commonly expressed as a range (allowing for the fact that the brake shoes are adjustable, typically over a 10-15 mm range.) For more information, see the article about caliper brakes.
from sheldon brown "The effective length of the arms of a caliper brake. This is measured from the centerline of the center bolt diagonally down to the middle of the brake shoe. Reach is commonly expressed as a range (allowing for the fact that the brake shoes are adjustable, typically over a 10-15 mm range.) For more information, see the article about caliper brakes.