How to Select a Master Cylinder - AIRHEART Brakes

1 AIRHEART brake A DIVISION OF TOL-O-MATIC, to Select a Master CylinderCylinder SelectionIn putting together a good vehicular braking system, selecting thecorrect Master Cylinder is Cylinder requirements are linked to pedal ratio. Therecommended pedal ratios are based on 150 pounds maximum forceon the lever to attain the maximum rated pressure for the mastercylinder. The mechanical advantage or pedal ratio, is the "A"dimension divided by the "B" recommended push rod cone angle is 5 degrees the bore size of the Master Cylinder is decreased and the mechanicaladvantage (pedal ratio) and push on the pedal remain the same, thefluid pressure (PSI) and the stroke both example, a 100 pound push on the pedal and 4:1 mechanicaladvantage (pedal ratio) gives a 400 pound push on the a 7/8-inch bore Master Cylinder , the piston area is squareinches and the pressure developed is 400= 667 stroke to move cubic inches of fluid is 1 a 3/4-inch bore Master Cylinder , the piston area is squareinches and the pressure developed is 400= 909 stroke to move cubic inches of fluid is a general rule, a person is able to exert approximately 150 poundsof pedal pressure, 75 pounds of lever pressure and 50 pounds of advantage of pedal ratioPedal ratio is best explained by referring to the following series ofdrawings.

2 Figures 1 and 2 are two basic types of "swing" pedalmounts. Figures 3 and 4 are the basic lever or floor mount each figure, the following values are:A Distance from pivot to mid-point of push or pull;B Distance from pivot to point of push on the Master Cylinder ;P Pivot point;F Force of distance in every case is from the pivot to the point of push onthe Master Cylinder or pedal regardless of which type of installation mechanical advantage or pedal ratio is the ratio of A to B (A:B).As A:B increases (that is as B gets smaller or A gets larger) with thesame push on the pedal (or pull on the handle) pressure will increase,but so will the example is a 1-inch Master Cylinder stroke and a 100 pound pushon the pedal. With a 4:1 ratio, the pressure is 4 x 100 = 400, and thestroke is 4 x 1 = 4 inches.

3 With a 5:1 ratio, the pressure is 5 x 100 =500, and the stroke is 5 x 1 = 5 MAXIMUMF 150 POUNDS"A""B"FP"A""B"F"A""B"PF"A""B"FIGUR E 1 FIGURE 2 FIGURE 3 FIGURE 4PF"A""B"3800 COUNTY ROAD 116 HAMEL, MN 55340 PHONE: (763) 478-8000 FAX: (763) 478-8080 pressureResidual pressure of8 to 12 PSI must be used with drum Brakes and isrecommended with caliper disc Brakes incorporating mechanicalretraction such as AIRHEART hydraulic that depend onseal deflection for retraction (such as all American manufacturedautomobile calipers) must not have residual pressure in the pressure is provided by a valve which is either a componentof the Master Cylinder or as an external valve plumbed into the linebetween the Master Cylinder and the the caliper is at the same level or higher than the mastercylinder,a 2 PSI Residual Pressure Valve is necessary (if an 8-12 PSIvalve is not used)

4 To prevent backflow fluid evacuation from thecaliper and,in turn,causing greater pedal travel to actuate the following diagram shows typical drag race brake systems with amaster Cylinder DRAG brake SYSTEMS WITH RECOMMENDED Master CYLINDERSYSTEM 1 COMPONENTSM aster Cylinders:One 1-inch boreFront Calipers:Two 175H brakesRear Calipers:Two 175X2 QCII brakesSYSTEM 2 COMPONENTSM aster Cylinders:One 3/4-inch and 7/8-inch boreFront Calipers:Two 175H brakesRear Calipers:Two 175X2 QCII brakesSYSTEM 3 COMPONENTSM aster Cylinders:One 7/8-inch boreFront Calipers:NONERear Calipers:Two 175X2 QCII brakesSYSTEM 4 COMPONENTSM aster Cylinders:Two 3/4-inch boresFront Calipers:NONERear Calipers:Two 175X2 QCII brakesSYSTEM 5 COMPONENTSM aster Cylinders:Two 7/8-inch boresFront Calipers:Two 175X2 QCII brakesRear Calipers:Two 175X2 QCII brakesSYSTEM 6 COMPONENTSM aster Cylinders:One 3/4-inch and 7/8-inch boreFront Calipers:Two 175X2 QCII brakesRear Calipers:Two 175X2 QCII Brakes AIRHEART brake A DIVISION OF TOL-O-MATIC, COUNTY ROAD 116 HAMEL, MN 55340 PHONE: (763) 478-8000 FAX: (763) 478-8080