On a 22SRR pump, you find O-rings at different locations (tank hose entrance, fill cap, sometimes as guiding joints).

The most important point: The material. The seals used in hydraulic braking must imperatively be in EPDM (ethylene-propylene).

• The danger: If you are using a "standard" O-ring (often in NBR / black nitrile bought in DIY store), it will swell, disintegrate and pollute your circuit in less than a few hours in contact with the Brake fluid DOT 4 /5.1.

On your 22SRR pump, the "pin" (pin or pivot axle) of 5x15mm is the piece that undergoes shear forces at each braking.

• Function: It serves as a hinge for the lever that operates the piston of the pump.

• Why a specific room? Unlike a metal rod cut at the right time, this pine is in Treated steel (tempered). If you are using a "soft" stem of hardware, it will dig and deform in a few tours, creating an important game in your pedal (the famous "blur" at the beginning of the race).

The 22SR EVO piston is a precision piece. Unlike appearances, it's not just a metal cylinder. It is machined with extremely low tolerances to allow the joints (cups) to slide without flee while generating a constant hydraulic pressure.

• The evolution "EVO": It guarantees a surface finish (polishing) optimized to reduce friction and increase the lifetime of the cups.