The stock Pickup and 4Runner master cylinder on 1979 – 1995 rigs are designed for discs brakes up front and drums in the rear. It does not have a residual valve for use with rear disc brakes. Without a rear residual valve in the system the rear disc pads expand after braking. This causes excess peddle travel the next time you step on the brakes. To solve this we sell a FJ80 brake master cylinder that is equipped with two residual valves, one for the front system and one for the rear. It’s 1″ bore size is larger than older 13/16″ bore cylinders for more fluid volume.