A brake control valve includes a housing, a quick braking chamber and a piston subject to brake pipe pressure on one side of the piston. A bore in the housing connects the quick braking chamber at a first end and the one side of the piston at a second end. A first valve is in the housing at the first end of the bore. A first operator is in the bore for opening the first valve for a range of positions of the piston. The bore has a first portion of a first diameter and a second portion of a second diameter larger than the first diameter. The first bore portion connects the one side of the piston to the second bore portion. A first operator in the bore is connected to the piston. A seal on the first operator is dimensioned to form a seal with the first bore portion and not with the second bore portion. The seal is located on the operator to lie in the first bore portion for a first segment of the range of piston positions and to lie in the second bore portion for a second segment of the range of piston positions.