TRF421X Front Knuckle Arm for 42391 - Tamiya 9803566  [9803566]

Front knuckle arm for TRF421X chassis

This aluminium knuckle arm is listed as Tamiya part number 9803566 and corresponds to the 42391 TRF421X assembly. It functions as a direct replacement for the front steering carrier on hobby-grade 1/10 scale touring cars that employ the TRF421X knuckle layout.

As the steering pivot, the knuckle arm transfers steering inputs to the wheel hub and affects alignment factors such as camber change and steering response. When maintaining or tuning a TRF421X-based chassis, swapping this part is a common way to address wear or to evaluate changes in steering behaviour.

Fitting the knuckle arm is standard RC maintenance: remove wheel and hub carrier fasteners, disconnect the steering linkage and any pins or retainers, fit the new knuckle arm, then reassemble while torquing to the vehicle manufacturer's recommendations and securing clips or set screws. After reassembly, check free hub rotation and confirm wheel alignment before running.

Tuning tip: replacing the knuckle arm can alter toe-in under compression and transient steering feel; make small adjustments and perform test runs to assess handling. Also inspect ball bearings, hex screws, and steering linkages for wear during the swap to ensure consistent behaviour.