Open class

Open class rules are based on the Official Tamiya Japan Cup regulations.

Machines

Usable machine types

Only Mini 4WD REV, Mini 4WD PRO, Racing Mini 4WD, Super Mini 4WD, Fully-Cowled Mini 4WD, Aero Mini 4WD, Mighty Mini 4WD, R/C Mini 4WD, and Truckin’ Mini 4WD machines are permitted. Further restrictions on machine types may be possible depending on the race event or race class.

Machine Assembly

All machines must be four-wheel drive. Modifications that result in rear-wheel or front-wheel drive are prohibited. Bodies should have stickers applied or be painted, and must be securely attached to the chassis. Please be warned that bodies which are particularly small, or those which it is difficult to check are painted or have stickers applied, may be prohibited. Home-made bodies are prohibited. All machines must go through car inspection and machines that do not pass inspection cannot participate in the race. As a general rule, machines must be assembled by the racer. Some exceptions may be applied. Please ask Race Officials.

Machine dimensions

All machines must have a 4WD setup and will be subject to the same measuring system as shown below.

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  • Maximum Car Width: Under 105mm

  • Overall Car Height: Under 70mm

  • Overall Car Length: Under 165mm

  • Minimum Ground Clearance: At least 1mm

  • Minimum Car Weight (including batteries and motor): At least 90g

  • Front and Rear Tires: Diameter: 22-35mm, Width: 8-26mm (Note that tires must be attached.)

  • Rollers: There is no limit on the amount of rollers that can be used.

  • Mass Dampers: The installation positions of rotating mass dampers are no longer limited.

When adding parts to the bumpers, side guards or the chassis, please note the zone restrictions below.

※Definition of Bumpers – For MS chassis, the bumper is the section on the Front or Rear Unit not including the Bumperless Unit. On other chassis, bumpers are the sections forward and rearward of the front and rear gearboxes respectively.
※Definition of Side Guards – Parts that extend from the sides of the chassis between the front and rear tires.

  • Parts which extend around the outside of the wheels to completely frame the chassis are not allowed.

  • Parts attached to the front bumper cannot extend past the line of the front axle.

  • Parts attached to the rear bumper cannot extend past the line of the rear axle.

  • Parts attached to the side guards must remain within the lines shown: (back edge of Front Tire & front edge of Rear Tire)

  • Chassis: Extension parts which are attached to the chassis itself are subject to the same zone restrictions as similar parts attached to the bumpers or side guards.

※There are no rules for parts which pass above or within the outside edges of the tires.
※There are no rules for mounting rollers, etc. to the body as long as they are above the level of the wheel axles. If they extend below this line, they will be subject to the same limits as parts which are attached to side guards.

Motor

Machines may use the kit-included normal motor, Rev-Tuned Motor, Torque-Tuned Motor, Atomic-Tuned Motor, Sprint-Dash Motor, Power-Dash Motor, Hyper-Dash 2 Motor, Hyper Mini Motor, Light-Dash Motor, Hyper-Dash 3 Motor, Rev-Tuned 2 Motor, Torque-Tuned 2 Motor and Atomic-Tuned 2 Motor. Mini 4WD PRO machines may only use the kit-included normal motor or motors designed for use with the Mini 4WD PRO series.

  1. Depending on the race event, other Tamiya motors may be permitted.

  2. For speed-limited race events or classes, if your speed exceeds the allowed limit, even the above motors may not be installed.

  3. Disassembling the motor to change the number of coils and other such illegal modifications are prohibited.

  4. If there are indications that the motor cap has been detached, it will be judged as being illegally modified.

Batteries

Only Tamiya-branded R6/AA/UM3 batteries are permitted. R/C Mini 4WD cars and TR-1 chassis cars may use alkaline batteries only. If the battery appears to be damaged in any way, they will not be accepted for safety reasons. Please note that some events may have different rules regarding which types or brands of batteries can be used.
In UK based races we recommend any brand of batteries are permitted, some events may specify and supply a control type battery.

Please follow the guidelines below when modifying your car. Also note that for modifications not listed, race officials will have the final absolute authority to grant or deny their use.

Modifications

  1. Chassis modifications are limited to cutting away plastic material or cutting holes out of the stock chassis. Homemade chassis and homemade parts are prohibited.

  2. Parts used for modification are limited to Tamiya Mini 4WD, R/C Mini 4WD, and Dangun Racer parts only.

  3. Part modifications are limited to cutting away the material or making holes in the stock part.
    Note: Original part shape must be clearly identifiable.

  4. Gear modifications are limited to making holes or shaving away material to reduce weight and installing ball bearings. All running gears must be installed according to the set gear ratios.

  5. Only kit-included battery terminals or Grade-Up Part battery terminals, installed according to the instruction manuals, may be used. Soldering or double-plated terminals are prohibited.

  6. Modifications that cause physical harm to the track, cause injury to any person, or release grease and/or other substances onto the track are all prohibited.

  7. Modifications to the tire’s shape are allowed if they comply with the Car Measuring System outlined above. However, changing the material properties of the tire surface (including, but not limited to, applying glue or other substances to the tire surface) are prohibited.