acting to actuate and load the shoe against the backing roll similar terminology is utilized with respect to the secondary piston and its nip loading force against the shoe through the secondary pivot rod when hydraulic pressure is applied to both the primary and secondary pistons less pressure is required in the primary piston to produce a predetermined nip loading force in pli of the shoe against the belt felts and web over the backing roll than would be required if the primary piston alone was used to provide the nip loading force further at a given nip load force in pli smaller hydraulic pressures acting on the secondary piston will maintain the corresponding resultant nip load force at decreasing offsets from the plane p in the downstream direction as shown in fig4 in other words the effective resultant nip load force 64 is located at a specific offset from plane p depending on the hydraulic pressure applied to the secondary piston as mentioned above and with reference to fig5 when hydraulic pressure is applied to the secondary piston 30 the hydraulic pressure required in the primary piston 22 is less due to the geometry selected to size the primary and secondary pistons in this case a primary piston having a 6 inch width and a secondary piston having a 3 inch width it has been found that at a given hydraulic pressure applied to the small piston half of that hydraulic pressure can be subtracted from the hydraulic pressure which would otherwise be applied solely to the primary piston to arrive at an actual or revised hydraulic pressure applied to the primary piston to effect and maintain.