Damper Piston 42391 for TRF421X - Tamiya 9803567  [9803567]

Piston Function and Fit

This Tamiya damper piston, referenced as part 42391, is made for TRF421X shock assemblies fitted to Tamiya scale RC cars. The piston serves as the internal flow metering element that governs oil passage through the shock, so it has a direct effect on damping response and rebound behaviour when used with appropriate shock oil and length settings.

The item is supplied as a replacement component for TRF421X maintenance or selective tuning; always verify the part 42391 reference against your shock parts list before ordering to ensure a correct fit. During service, check piston surfaces and shock shafts for wear and replace any damaged seals or spacers in accordance with the TRF421X service routine.

In practical tuning, swapping piston types or reversing piston orientation changes how oil flows and can refine mid-speed and low-speed damping behaviour without altering spring rates or the shock body, making piston swaps a straightforward method for iterative setup testing.