Tamiya - RC TRF421X Chassis Kit

TRF421X Chassis Kit

TRF421X incorporates racers feedback from the past year to refine the 2 belt-driven 4WD platform with updated suspension and low center of gravity setup options for superior performance on high-traction track conditions.

This chassis features a newly designed aluminum motor mount that positions the motor 1.04 mm lower than on the TRF421 chassis kit, lowering the center of gravity for improved stability and more confident cornering. A contemporary, precision-focused design ensures accurate assembly and consistent performance. Complementing this is a new 2.0 mm–thick aluminum lower chassis deck, which allows the lowered motor position while optimizing balance, chassis flex, and weight distribution. When used together with the new aluminum motor mount, the lower deck is also compatible with the standard TRF421 chassis.

Both one-piece and two-piece upper chassis decks have been updated to refine chassis flexibility and handling response. The one-piece upper deck mounts using tubes, dedicated titanium low button-head screws, and shims, allowing fine adjustment of chassis flex with 0–0.3 mm shims. These upper deck components are fully compatible with the standard TRF421 chassis, offering easy upgrade paths and setup versatility.

Suspension performance has been further enhanced with new front and rear damper stays and upper and lower suspension arms molded from carbon reinforced nylon. Compared to the glass reinforced nylon used on the TRF421 kit, this new material delivers more controlled flexibility and improved stability, particularly in high temperatures, high-grip conditions, or on carpet tracks. The damper attachment positions have been moved 1.0 mm inward to refine suspension geometry and handling consistency.

The drivetrain has been refined to reduce friction and improve durability. A new front double cardan driveshaft and rear lightweight aluminum universal shafts now incorporate bearings, replacing the swing shaft caps used on the TRF421 kit. In addition, the front direct spool cups and rear differential have been redesigned, with materials changed from aluminum to steel for greater strength and long-term reliability.

Steering and suspension geometry updates further enhance responsiveness and grip. New upper arm mounts feature a 1 mm narrower pivot width for sharper cornering response, along with bushing-based pitch adjustment and a vibration-resistant modern design. Updated knuckle arms introduce revised hole positions: the front promotes a more outward Ackermann position for more direct steering feel, while the rear shifts adjuster rod attachment rearward to improve rear grip on low- to medium-traction surfaces. Precision stabilizers are included in 1.2 mm (two pieces) and 1.3 mm (one piece) diameters, allowing tuning to suit track conditions and driving style.

To fine-tune overall balance, newly added weights include a 20 g receiver weight and a 0.6 mm–thick 30 g battery weight. The receiver weight mounts with a single screw and also functions as a cooling fan mount, contributing to both balance and thermal management. Most components are compatible with the standard TRF421 chassis, making this an ideal performance-focused upgrade or standalone platform.

Required to complete the model are a 2-channel radio system, low-profile steering servo, ESC, 540 motor, wheels and tires, a 190 mm touring car or sports car body, a 7.4 V battery pack, and a compatible charger.

Key Features