Most Mini 4WD cars, except those from Wild Mini 4WD series and Original Mini 4WD series, can be used in races. Depending on the race classes, usable machine types may be further restricted. Although not indicated, R/C Mini 4WD cars are prohibited from entering races.
All Mini 4WD cars must be four-wheel drive (thereby banning Mini-F cars), and the bodyshell must be applied with decals or painted, at the minimum. The use of home-made bodyshells and bodyshells made from the leftover of the cut-off bodyshells are prohibited. A Mini 4WD car 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 (2020 special rule)
Gear ratio: For single shaft chassis: 3.5:1, 3.7:1, 4:1, 4.2:1. Must be matching gear sets, For Double shaft/Pro Chassis: 3.5:1, 3.7:1, 4:1. Must be matching gear sets.
Mass damper: racers can freely install a rotatable mass damper anywhere on the chassis, as long as they are within the maximum width.
In addition, the roller stays must not extend beyond the front and rear driveshafts.
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 any official race tournament. There is no restriction on the usable motors for the double-shaft motor powered Mini 4WD cars. Disassembly of the motor or use of unofficial motors from other brands are prohibited.
Usually, only the Tamiya-branded AA batteries may be used. For TR-1 Chassis cars, the use of Alkaline batteries is a must. Batteries would be rejected if they appear to be damage in any way. On some tournaments, organizers may allow 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. Incompatible roller modification, such as using plastic rings on incompatible rollers and modifying plastic rollers (that doesn't have native support for ball-bearings) to have the ball-bearings inserted, are prohibited. Attaching HG aluminum setting boards, setting gauges and pinion pullers to the car are prohibited.
Racers can combine the different tire material into one wheel, as long as the wheels themselves (especially the hook) doesn't touch the road surface and racers doesn't change the material of the tire surfaces.
Gears may be only modified by cutting out holes and/or shaving away part of them, and a Mini 4WD car's running gear must be installed according to the set gear ratio. Modifications deemed harmful to the race track or any person, or spilling oil or other substances onto the track are all prohibited.
The use of soldered or double-plated terminals are prohibited.
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.
The start of the race will be indicated by a signal from either the race official or an automated starting signal system. Racers will switch on their cars, hold them over the start ramp with one hand, and drop them vertically into their assigned lane at the start signal. if a racer does any action that breaks other racers' concentration before the start signal, such as using a camera's flash, they are immediately disqualified from competing in that day's races. 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 fly off the track, being flipped over, jumps onto another lane, the car's bodyshell completely detaching 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.
All racers' cars must undergo inspection by the car inspectors before they can enter the race. If the car did not 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 after the car inspection and before the race. Car inspection can occur at any time in a race tournament.
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.
Competitor was found applying grease or other substances onto the track to affect track surface conditions.
Modification of a car after it had passed the car inspection.
Refusal to follow the instructions of race officials or any actions that impedes the operations of the race track.
Engaging in a false start, or is determined to have thrown or pushed their cars forward at the start of a race.
At organizer's discretion, found to have acted against the spirit of fair play or caused distress to other participants.
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.
It should noted that some race classes has age limitations. With the exceptions for endurance races, it is against the regulations to have more than two racers using the same car.