A clamp assembly of a vehicle leaf spring suspension is disclosed. The clamp assembly has an axle bracket secured to a vehicle axle and a top cap secured to the axle bracket by mechanical fasteners to define an axle seat. The axle bracket and top cap may include interlocking keys and keyways to cooperate with the mechanical fasteners in transmitting the load from the vehicle axle. A spring seat of the leaf spring is received within the axle seat and is tapered. The tapered spring seat, when combined with a deformable liner in the axle seat, effectively eliminates the inactive portion of the leaf spring to increase the effective length of the spring and minimize the spring rate.