The Wilwood 1-inch-bore tandem master cylinder with remote reservoirs comes with internal residual pressure valves for drum brakes in both the front and rear outlets. Per the instructions, we removed this spring and rubber seal from the front circuit, which is where we’ll hook up our disc brakes. Like most systems, the rear-most output on the master cylinder is for the front brakes. When sizing the bore of a master cylinder there are several things to take in to account; drums, discs, vacuum boost and so on. The easiest thing to do is to call the folks at Wilwood Tech and Sales support to help you figure out what bore size you need when ordering a master cylinder.