We have a pressure reducing valve, P/N 260-8419, and we recommend its installation with front brakes. With discs on both the front and rear the percentage could be higher depending on the weight distribution and tire size but should still use the pressure reducing valve. This is especially important when using drum brakes on the rear. A starting point would be 70% of the rear line pressure to the front brakes. Because of the small front tire contact area compared to the rear large slick contact area, the rear brakes must absorb more of the stopping energy than the front (contrary to a normal street car). When any four piston caliper is used with drum brakes on the rear, a pressure reducing valve must be installed for front pressure control. Several considerations must be taken into account when installing these kits. The main advantage is the reduction of weight compared to the stock braking system they are designed to replace. Proportioning (Pressure Reducing) Valve The front brake kits with the integral hub and adaptor are designed for Drag Race applications. This allows the bleeder to be highest point, ensuring that all air is removed from system. To bleed the system, the calipers must be positioned at 3 or 9 o’clock.
Drag racing master cylinder install#
Install your wheels to make sure the caliper to wheel clearance is adequate both radially and from outer face of the caliper to the inner face of the wheel. Misalignment can cause caliper mount deflection which is one of the causes of a “spongy” pedal. 015” ( MW catalog page 63 or online P/N 71009). Shims are available to correct the alignment moving the disc outward. See the chart below for stand out dimensions for MW brake kits. Install the axles and check axle standout (face of axle flange to face of housing end) as accurately as possible. To check stand out, first verify that the housing ends are square to the tube and axles. Master Cylinder Displacement (1.25" Stroke)Ĭaliper Alignment Clearance and Position Axle stand out controls the alignment of the brake system and as a result is extremely critical. First find the correct caliper combination from the chart, then find the correct ratio for your master cylinder size. A balanced system includes the following things: 1) A lever that moves the entire stroke of the master cylinder 2) A Lever that moves comfortably in the confines of a car 3) Uses a reasonable amount of force to reach the desired system pressure 4) Is aligned well enough to minimize lever travelīelow is a calculator to help you find the correct ratios. Pedal force, system pressure and lever travel all need to be taken into account. The goal then is to balance the entire system. For instance, moving from a 3/4" master cylinder to a 1" requires 77.7% more force on the push rod. The result after adding the larger master cylinder is a harder pedal which needs much more pedal pressure to create the same amount of braking force.
While a larger master cylinder will take up system slack with less pedal stroke, it will take more force to create the same system pressure. While a larger master cylinder creates a larger displacement, it takes more force to create the same pressure as a smaller bore. One of the most common misconceptions is that a larger master cylinder will create more pressure. Slack comes from two factors: retracted pistons must be moved back out, and misalignment caused by deflection in the axle and housing mis-alignment. Brake systems inherently have slack in the system that must be taken up before work can be done by the pads.
If the desired pressure can not be easily attained the pedal ratio must be increased until the minimum pressure of 1000 psi is easily reached.Ī common problem in many applications is a spongy pedal. We recommend using a pressure gauge connected to the system to verify the maximum available pressure before running the car. A pedal ratio versus line pressure calculator is available below. With the correct master cylinder in place, the pedal ratio must be great enough to produce 1200 psi system pressure under severe braking conditions. Mounting the master cylinder to a frame rail or roll bar is recommended to ensure a solid mount.
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