PSA

Piston Surface Area (PSA)

What do you want? 4 Piston, 6 Piston, 8 Piston, 12 Piston. Whay so many? Is more better? Does the number of pistons make the caliper clamp more on the rotor? Let's clarify piston questions right now. It's simple and without question. Clamping force is line pressure times piston surface area.

In a given location, you cannot put 6 pistons with the same surface area as four pistons. The six pistons will always be smaller in overall surface area. Also, some manufacturers would have you believe that six pistons spread the force more evenly over the back of the pad. However, even if they did gain here, (which they don't), the resultant weaker caliper as a result of placing a piston in the key stress area of the caliper, creates a far weaker caliper.

Use the formula below to calculate your Total Clamping Force (TCF).

CLAMPING FORCE = PISTON SURFACE AREA (ONE SIDE OF ROTOR) x LINE PRESSURE

See the chart below to calculate your Total Clamping Force (TCF) from your caliper.

Diameter of Piston	Radius (equals 1/2 diameter)	R2	Piston Surface Area
			(radius squared x PI)
0.50000	0.25000	0.06250	0.19635
0.62500	0.31250	0.09766	0.30680
0.68750	0.34375	0.11816	0.37122
0.75000	0.37500	0.14063	0.44179
0.81250	0.40625	0.16504	0.51849
0.87500	0.43750	0.19141	0.60132
0.93750	0.46875	0.21973	0.69029
1.00000	0.50000	0.25000	0.78540
1.06250	0.53125	0.28223	0.88664
1.12500	0.56250	0.31641	0.99402
1.18750	0.59375	0.35254	1.10753
1.25000	0.62500	0.39063	1.22718
1.31250	0.65625	0.43066	1.35297
1.37500	0.68750	0.47266	1.48489
1.43750	0.71875	0.51660	1.62295
1.50000	0.75000	0.56250	1.76714
1.56250	0.78125	0.61035	1.91747
1.62500	0.81250	0.66016	2.07394
1.75000	0.87500	0.76563	2.40528
1.81250	0.90625	0.82129	2.58015
1.87500	0.93750	0.87891	2.76116
1.93750	0.96875	0.93848	2.94831
2.00000	1.00000	1.00000	3.14159
2.12500	1.06250	1.12891	3.54656

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