TRF421X Upper Arm Nut Threaded Locking Pivot - Tamiya 9803565  [9803565]

TRF421X Upper arm nut details

This is a replacement upper arm nut for the TRF421X chassis, supplied as the Tamiya 9803565 spare part. It functions as the fastening element at the upper arm pivot, keeping suspension geometry fixed while you adjust ride height, camber, and other fine settings.

Compatibility is with TRF421X-series suspension assemblies as indicated by the part reference 42391. When installing this nut, start the threads by hand to prevent cross-threading, ensure mating surfaces are clean, and finish with the correct hex driver or wrench. Do not over-tighten because excessive force can damage plastic or composite arm inserts.

During setup and tuning the nut holds pivot position under load so alignment changes at the shock and turnbuckle stay consistent. Inspect the nut regularly during practice laps and re-check thread engagement whenever you swap arms or replacement components.