A slack adjuster for use with a railway braking system which has an increased let-out length that enables the use of brake shoes having an increased thickness. The slack adjuster includes at least oneof a dual spring and canister assembly, an external yoke trigger, or a combination of both a dual spring and canister assembly and an external yoke trigger. A method of retrofitting a truck mounted brake system is provided, in which the slack adjuster is positioned within the brake system in order to increase the let-out length while maintaining a predetermined spatial envelope within the brake system. The slack adjuster has an increased let-out length enabling the use of thicker brake shoes without requiring modification of the interacting components of the truck mounted brake system since the overall size of the slack adjuster remains the same.