GB-03
The GB-03 chassis is a completely new development for Tamiya in the world of 1/16 scale radio-controlled buggies; Tamiya designs and develops a four-wheel drive chassis that is entirely new.
The four-wheel drive, side battery access, different electronic layout and other small innovations require a clear change in the shape and concept of the chassis compared to all previously developed models in the GB-0X series. The chassis is now made of two shells and is no longer an open tub design.
The following factory-assembled model is part of the GB-03 Tamtech Gear family by Tamiya:
– Hot Shot mini, model number 56711, released in 2007 and available on the market until 2008. It is a scaled-down reproduction of model 58047 – Hot Shot
In this case, the mini version is not an entirely faithful replica of the original version: the front mono-shock system is common to both versions, but they differ in the rear suspension system, where the original model features a mono-shock system that becomes a dual-shock system in the mini version.
Tamiya uses some parts that are shared with previous two-wheel drive chassis models GB-01, GB-01S, GB-01T, GB-02 and GT-01. Other parts are specifically developed for this four-wheel drive chassis. Technically, the chassis has the following features starting from the rear and moving toward the front:
– Four-wheel drive powered by a type 370 motor with a Teflon pinion gear (see the four factory-supplied pinions with 12, 14, 16 and 18 teeth highlighted in the image below on the left in the first row). Technical specifications of the RK370 motor at maximum efficiency: 10,600 revolutions per minute, torque 5.4 Nm and current draw 1.8 Amps. To improve performance, install accessory number 40537 described as “Tamtech-Gear Sports Tuned Motor SPT”
– Independent suspension with double wishbone arms. At the front, the model features a mono-shock absorber reminiscent of the original 1/10 scale Hotshot design (see image below); at the rear, the model features dual shock absorbers inspired by the original 1/10 scale Hot Shot II design. The front suspension is stiffer than the rear and includes a stabilizer bar to optimize the action of the mono-shock. All three shock absorbers are red coil springs.
A solution is available to replace the red shock absorbers and improve performance: set number 22011 described as “TamTech-Gear GB-01S CVA Damper Set (4pcs.)”; if available, the blue version code 40529 can also be used. When updating the GB-03 chassis with this set, three technical upgrades can be carried out to significantly enhance performance.
First upgrade: replacement of the shock absorbers. Set 22011 includes four yellow shock absorbers (three are used for the GB-03 chassis). This set is designed for the GB-01 chassis and includes two long rear shock absorbers and two short front ones. The three shock absorbers on the GB-03 chassis have the same travel; when assembling the front shock absorber, remove the insert to reduce the stroke.
Second upgrade: set 22011 also includes twelve yellow plastic ball joints to be used for the steering (four pieces; two for the right arm and two for the left arm) and upper suspension arms (eight pieces; two for each arm of the four independent suspensions). To build the arms, add threaded rods to screw into the ball joints: a total of six threaded rods are needed because two are used for the steering arms and four for the suspensions. The threaded rods are included in set number 22017 described as “2.6 x 29 mm Aluminium turnbuckle shaft (6 pcs Blue colour)”.
Third upgrade: to complete this technical update, replace the factory-installed plastic threaded ball pins with aluminum ones: set number 40525 described as “GB-01 Aluminum 4mm Ball Connectors Blue colour” (contains 10 pieces, 12 are needed).
Front and rear planetary gear differentials previously installed only on the GB-01S chassis. This new differential is identified by code SP-1685 or 51695 described as Tamtech Gear GB-01S Spare Gear; it is more robust than the factory-installed ball differential on the GB-01 chassis.
The second function is to protect the gears from premature wear when the motor, during sudden acceleration, increases its rotation speed faster than the wheels can respond. The same occurs during sudden deceleration. The clutch prevents the model from losing traction and avoids unnecessary stress on the gears.
The clutch plays this dual role, ultimately preserving the mechanics inside the gearbox, where the most stressed gear is the motor pinion.
To achieve optimal performance, it is necessary to adjust the slip by acting on the calibration setting (indicated as “BA9” and highlighted in red in the image above on the left). Follow the instructions by compressing the spring until reaching a total length of 4.2 mm to find an initial operating point for the anti-hop clutch. Place the model on a table or flat surface, turn on the electronics, hold the rear wheels with your hands and give a short burst of acceleration. There are two possible outcomes: the model tends to move and the front end with the front wheels lifts off the surface (following the green line shown in the image below), or a noise is heard from the gearbox indicating that the clutch is functioning and the front end of the model does not lift off the surface. In the image, the hand is shown holding the rear wheels and the movement that the front axle should make in response to the acceleration burst is highlighted by the red arrow.
The best configuration is when the front end and front wheels lift slightly off the surface, losing contact with the ground; this is only a starting point. The optimal setup depends on the track surface conditions and its grip level; calibration must be adjusted accordingly.
The two worst configurations are the extremes of adjustment: the spring being too compressed or too loose. In the first case, the gears are directly and firmly connected to the wheel axle and the clutch completely loses its function. In the second case, the spring is so loose that it does not transmit any movement to the wheels, making it impossible for the model to move. In the Tamiya universe, the first anti-slip clutch called TTC (short for Tamiya Torque Control) was engineered for the Super Astute, which was released in 1991.
– GB-03 is equipped with a complete set of ball bearings. The gearbox, front axles and rear axles are fitted with ball bearings, while the shaft between the front and rear gearboxes uses 850-size bushings. To improve performance, the two 850-size bushings can be replaced with two ball bearings of the same size. For further performance enhancement, the plastic shaft can be replaced with a blue anodized aluminum shaft, code 40558 “GB-03 Aluminum Propeller Shaft (Blue)”.
– The central chassis made of two half-shells follows the concept of the Hot Shot chassis with a transverse battery, which can be accessed by removing it from the side. This solution ensures a low overall weight and lowers the model’s center of gravity.
– The transparent Lexan body, factory-painted in red, perfectly replicates the shape of the Hot Shot model from the 58xxx series. As a spare part, an unpainted Lexan body is available on the market under code 40170 “RC Body Hotshot 4WD Body Parts Set”
– Most of the screws used in models equipped with the Tamtech Gear GB-03 chassis have an M2.6 thread.
– The remote control system is based on AM technology at 27MHz and consists of the Expec SP TTU-03 transmitter (code 17254324 or 7254324) and the TRU-02 receiver (code 45036). The onboard electronics include the TSU-02 servo and the TEU-102 BK ESC (image taken from the packaging). As of today (2025), these components are no longer available on the market. Note that the TEU-102 BK does not have a “cut off” function and therefore cannot be used with Lipo batteries. Lipo batteries must not be fully discharged, so in the absence of a “cut off” function, it is advisable to replace the electronic speed controller if you intend to use next-generation batteries.
List of all parts that are accessories to improve performance or parts not included in the factory GB-03 package; some accessories are shared with the GT-01 family and other GB-01xx families:
22011 TamTech-Gear GB-01S CVA Damper Set (4pcs.)
22012 TamTech-Gear GB-01S Setting Spring Set
See image below showing how to install the springs from accessory number 22012 according to the color, which corresponds to their stiffness: lighter springs are stiffer than darker springs.
22013 TamTech-Gear GB-01S Wheel Collar (Blue) & Bolt Set, alternate code 40523
22014 TamTech-Gear GB-01S Aluminum Wheel Hubs (Blue 2pcs.), alternate code 40526
22017 TamTech-Gear GB-01S 26x29mm Aluminum Turnbuckle Shaft (Blue 4pcs.), alternate code 40524
40525 GB-01 Aluminum 4mm Ball Connectors (Blue colour)
22021 TamTech-Gear GB-01S 05 Hard Coated Aluminum Pinion Gear (16T)
22022 TamTech-Gear GB-01S 05 Hard Coated Aluminum Pinion Gear (18T)
54919 Torque Tuned motor, equivalent to RK-370-SD-3265; technical data at maximum efficiency: 15,000 revolutions per minute, torque 6.8 Nm, current draw 2.1 Amps. Alternate code 40514
54860 Sport Tuned motor, equivalent to RK-370-SD-4045; technical data at maximum efficiency: 21,000 revolutions per minute, torque 7.7 Nm, current draw 3.3 Amps. Alternate code 40537
51685 TamTech-Gear GB-01S Spare Gear Set
54928 Metal Cross Join. See image below for how to install set number 54928. This accessory becomes necessary if you decide to install the 54860 “Sport Tuned motor”.
There are several alternatives for installing tires that offer excellent grip on various types of surfaces. It is possible to install the tires from the GB-02 TamTech Buggy Champ chassis, which fit the rims of the GB-03 chassis. The codes are:
– Set number 40155 described as GB-02 front tires, which are the factory-installed tires on the GB-02 chassis
– Set number 40156 described as GB-02 rear tires, which are the factory-installed tires on the GB-02 chassis
Alternatively, the same tires are available with foam inserts to make the sidewalls stiffer:
– Set number 40542 described as GB-02 front tires
– Set number 40543 described as GB-02 rear tires
These tires fit the following rims that can be installed on the GB-03 chassis:
– Set number 40109 white front rims factory-installed on The Frog mini, The Hornet mini and Desert Gator
– Set number 40110 white rear rims factory-installed on The Frog mini, The Hornet mini and Desert Gator
– Set number 40552 chrome front rims, equivalent to 40109 in chrome, accessory sold separately, never factory-installed on any model
– Set number 40553 chrome rear rims, equivalent to 40110 in chrome, accessory sold separately, never factory-installed on any model
– Set number 40133 gold-plated front rims factory-installed on The Fox mini. This option best replicates the wheels of the 1/10 scale Hot Shot model
– Set number 40134 gold-plated rear rims factory-installed on The Fox mini. This option best replicates the wheels of the 1/10 scale Hot Shot model
– Set number 40160 white front rims available in the GB-01 kit code number 57102, chassis only
– Set number 40161 white rear rims available in the GB-01 kit code number 57102, chassis only
