The official Mini 4WD race regulations (Japanese: ミニ四駆公認競技会規則, Mini Yonku Kōnin Kyōgi-kai Kisoku) is a set of rules set by Tamiya for Mini 4WD race tournaments.

About the rules

Since the first Japan Cup, Tamiya create the race regulations so racers can races fairly. Organizers and racers must adhere to those rules when entering the tournament.

It should be noted that the rules will changes annually, so a racer has to check out the rules so he/she wouldn't violates any of the rules set by the regulations.

Regarding Mini 4WD cars

Usable Machine Type

Most Mini 4WD cars, except those from Wild Mini 4WD series and Original Mini 4WD series, can be used in the race. Depends on the race classes, usable machine type may be further restricted.


All Mini 4WD cars must be four-wheel drive, and the bodyshell must have the sticker applies or be painted. It should be noted that home-made bodyshells and bodyshell made from the leftover of the runners may be prohibited. A Mini 4WD cars must be assembled by the racers themselves.


All Mini 4WD cars must be within the measurement ranges as set by Tamiya:

  • Max length: 165mm
  • Max width: 105mm, with all GUPs attached
  • Max height: 70mm, with spoilers and GUPs attached
  • Minimum ground clearance: Over 1mm from flat surface
  • Tire diameter: 22 to 35mm for both front and rear tires attached to the wheels.
  • Tire width: 8 to 26mm for both front and rear tires attached to the wheels.
  • Minimum weight: Over 90g, with battery attached.
  • Rollers: Unlimited (2018 special rule)
  • Gear ratio: must be the matching gear sets
  • Mass damper: racer can freely install the rotatable mass damper to anywhere, as long as they are within the maximum width.

In addition, the roller stays should not extend pass the front and rear driveshafts.

Usable Motor

For single-shaft motor powered Mini 4WD cars, the original Hyper-Dash Motor, Turbo-Dash Motor, ZEN-Tuned Motor, Jet-Dash Motor, Ultra Dash Motor, Mach-Dash Motor and Plasma-Dash Motor, cannot be used in race tournament. There is no restriction on the usable motor for the double-shaft motor powered Mini 4WD cars. Dissemble the motor is prohibited.


Usually, only the Tamiya-branded AA batteries may be used. For TR-1 Chassis cars, the use of Alkaline batteries is a must. The battteries would be rejected it they appear to be damage in anyway. On some tournaments, organizers may allows of use of AA batteries from other brands.


The chassis can be only modified by cutting away parts and/or cutting out holes on them. Homemade chassis and homemade parts (i.e. those that are not modified from Tamiya's GUPs and/or AO parts) are prohibited.

In most race events, only Tamiya-branded parts, modified or not, may be used. However, modified parts must be modified in the way that the car inspectors can identify what parts they are using. Racers can combine the different tire material into one wheel, as long as they don't change the material of the tire surfaces. Gears may be only modified by cutting out holes and/or shave away part of them, and a Mini 4WD car's running gear must be installed according to the set gear ratio. Modification that can cause harm to the race track, cause injury to a person, or spilling oil or other substances onto the track are all prohibited.

The use of soldering and double-plated terminals are prohibited.

Regarding race courses

For race tournaments, an organizer must make sure that their circuit is within the exact measurement as set by Tamiya:

  • Individual lane width: 115mm
  • Fence height: 50mm
  • Adjusting the height and lane width of lane change sections, bank turn sections, etc. for smoother racing operations is permitted.

Regarding compete in the race tournament

The start of the race will be indicated by a signal from either the race official or a automated starting signal system. Racers will switch on their cars, hold them in the air with one hand, and drop them vertically into their assigned lane at the start signal. Doing things that breaking other racers' concentration before the start signal was shown, such as using camera, are prohibited. It should be noted that throwing or pushing the car forward is also prohibited.

There are five ways in which a racer is immediately retired from the race. This includes having the car flying off the track, being flipped over, jumps onto another lane, the car's bodyshell completely detached during the race, and blocking the progress of other racers.

The car's race is finished when it cross the finish line, and qualifying and final positions are determined by either the race finishing order or Time Attack time.

Regarding car inspection

All racers' cars must undergo the inspection by the car inspectors before they can enter the race. If the car didn't pass the inspection due to violating the rules, a racer must make necessary change to the car in order to enter the race. Racers are not allowed to modify their car during after the car inspection and before the race. Car inspection can occur at any time in a race tournament.

Regarding disqualification

A racer would be disqualified if:

  • Their car is determined to have modifications that will cause physical harm to other racers, other cars, or the race track.
  • Their car is is determined to have modifications that are designed to deliberately obstruct other cars.
  • He/she deliberately puts grease or other substances onto the track to affect track surface conditions.
  • He/she is determined to have modified his/her car after it had passed the car inspection.
  • He/she does not follow the instructions of race officials or otherwise impedes the operations of the race track.
  • He/she has a false start, or is determined to have thrown or pushed their cars forward at the start of a race.
  • He/she is determined to have acted against the spirit of fair play or caused distress to other participants.

Regarding race operation

Any racer can raise their objection to the race official. However, these objections must be made before the next race begins.

In addition, race officials may reserve the right to announce the use of special regulations at any time during the race.

Regarding participant restrictions

It should noted that some race classes has age limitation. With the exceptions for endurance races, it is against the regulations to have more than 2 racers using the same car.

Regarding manners

In Tamiya-sponsored race tournament, particularly those in Japan, racer is not allowed to bring any battery charger, electrical component that use to break-in the motor, motor checker and battery warmer to the race track. So is the spray can, due to being highly flammable. Sanding parts at the race tournament is not allowed, due to the danger of having the sanded dusts inhaled.

Because the locations where the race tournament was held are mostly anti-smoking area, smokers are advised to move to the place where smoking is allowed. Drinking any kind of alcohol drinks at the race tournament is also not allowed.