Yokomo YOKYS8D Diaphragm Cap Upgrade for Yokomo/Associated Shock Bodies  [YOKYS8D]

Diaphragm cap technical briefing

This diaphragm shock cap set is made for Yokomo and Associated shock bodies and replaces the normal solid cap with a flexible nitrile membrane. The design helps maintain internal pressure, cut down oil aeration, and keep damping responses more consistent over repeated compressions.

Compatibility is restricted to the brands shown in the product name; confirm that the cap form matches your shock body before fitting. By keeping oil shielded from air, the diaphragm reduces foaming and helps deliver repeatable damper behavior throughout a session.

To install: remove the shock from the car, handle or drain oil as required, remove the original cap, seat the diaphragm flush with the shock body, and reassemble carefully to avoid catching the seal. Cycle the shock slowly after fitting to ensure smooth movement and no leaks.

As part of a tuning plan, use the diaphragm to protect oil performance rather than as a tuning element itself; it helps your chosen springs and oil remain stable between runs and reduces variable damping from aeration.