On the step bore OBS MC, the primary bore pushes high volume up to a certain pressure then transitions to the smaller secondary bore and begins to develop pressure at a more rapid rate.
I know this is an ancient thread,,, but, the purpose of the "step bore" MC is somewhat diff from above.
The step bore MC is made to supply "high volume/low pressure" to the rear drum brakes with the large bore piston.
The small piston supplies "low volume/high pressure" to the front discs.
The two pistons are separated by brake fluid, and their is no "transition of pressure" from low to high.
Each piston operates its respective circuit in an independent manner.
The "transition" type, or "quick take-up" MC, is used for the new "low drag" all disc systems, and it uses three pistons,, but is not like the "step bore" MCs on the older rigs.
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