Tamiya TRF421 Chassis Kit

The Tamiya TRF421 Chassis Kit (part number HC-42384) is a 1/10 scale, two-belt 4WD carbon fibre double-deck platform from the TRF series. Released on 31/05/2024, it debuts an updated drivetrain, revised lower and upper decks, A-shaped upper suspension arms, adjustable caster, and shorter dampers to deliver stable, efficient on-road performance.

Compared with the TRF420X (Item 42382), the TRF421 moves the motor 22.7mm toward the chassis centre, and employs identical-length front and rear drive belts for balanced handling and drivability. A revised spur gear and belt layout uses a single dedicated nut, streamlining maintenance and setup changes at the track.

Key Features

• 1/10 scale R/C chassis assembly kit.
• Two-belt 4WD drivetrain with the motor relocated 22.7mm toward the chassis centre versus the TRF420X; equal-length front and rear belts support stable drivability.
• Updated spur gear mounting uses a single dedicated nut for quicker, more efficient maintenance.
• New, smaller lower deck reduces ground contact when the chassis experiences roll.
• Choice of one-piece or two-piece upper deck; five total setup patterns available by changing screw positions.
• A-shaped upper suspension arms increase rigidity; longer lower arm spans limit swing width to enhance stability during roll.
• Front and rear suspension layouts change from blocks to balls; roughly 7mm-longer arm spans further improve stability.
• Toe angle adjustable via uprights (lower arm inner toe angle is 0 degrees).
• Three damper attachment positions (inner, middle, outer) on front and rear lower arms provided via two types of aluminium bushings.
• Shorter dampers are employed.
• Adjustable front and rear caster angles.

The TRF421 focuses on consistent handling and tuning flexibility. Longer arm spans and the A-shaped architecture work to keep the car composed as it rolls, while the upper deck options and simplified spur gear fixing make it easier to fine-tune response and carry out rapid changes between runs. As a modern carbon fibre double-deck touring car chassis, it embodies the latest TRF thinking for competitive on-road racing.