Tamiya 9803567 Damper Piston (Part 42391) for TRF421X  [9803567]

Replacement Piston: Key Details

This Tamiya spare piston is identified as part 42391 and is intended for installation in TRF421X shock assemblies used on Tamiya scale RC cars. The piston meters oil flow inside the shock body and therefore influences damping response and rebound behaviour when paired with suitable oil and the correct shock length settings.

It is supplied as a direct replacement for TRF421X suspension maintenance or targeted setup work; confirm part 42391 on your shock parts list before purchasing to ensure compatibility. When rebuilding shocks, inspect piston faces and shock shafts for scoring and change any worn seals or spacers in line with the TRF421X rebuild procedure.

For tuning, changing pistons or their orientation modifies the oil flow path and can be used to adjust mid-speed and low-speed damping behaviour without replacing springs or the shock body, which makes piston swaps a practical tool for step-by-step setup changes.