Competition Class Primer

Open Class 

Open Class mirrors the official Tamiya Japan Cup regulations.   As it has the least number of restrictions, it is the heart of Mini4WD competition and is therefore the most fundamental of all the competitive classes.  The limited restrictions also result in what is considered to be the most advanced of the classes.  It is particularly characterized by the extreme modifications racers make to their machines to make these the fastest and most stable in all of Mini4WD competition.  The necessary ability of the racer to build their car in Open Class extends past kit assembly to include the use of tools to modify parts for different and creative purposes.  

In general terms, as long as a machine is made from parts the race official can recognize as in coming from the Tamiya catalogue, anything goes.  And if you do it well, it goes very, very fast.

Tuned/Basic-MAX (B-MAX)

Tuned class was designed to allow racers the ability to race machines fitted with add-on parts, like rollers and mass dampers, but without the need to have advanced tools or ability to modify the cars body, chassis, or parts themselves.  Its popularity among racers limited to 3-lane track resulted in a formal codification of the ruleset and the launch of the Basic-MAX Grand Prix in 2021.  The B-MAX rules are an “updated” and living ruleset that aims to provide a standardized ruleset for the Tuned level of racing.  As such, the terms Tuned and B-MAX are often used interchangeably.  However, it is very important to know the differences.  Albeit minor, the details can mean the inclusion or exclusion of a particular machine come race day.

Compared to B-MAX, Tuned is a more restrictive version of B-Max as it limits machines to Rev motors and has a strict no-cut/no-modification rules for body, chassis, and plate.

Compared to Tuned, B-MAX is an ever-so slightly more expansive version of Tuned Class that allows Dash motors.  Additionally, it allows some minor modifications to body, chassis, and plate for the purpose of accommodating more part/chassis combinations along with some generally accepted best practices.  In short, a machine built to Tuned regulation can run B-MAX.  However, a B-MAX machine might not qualify for a Tuned class race.  Check your event’s specific regulation to make sure.

Special Note:

In relation to other classes, these “mid-level” classes are the most important for racers to read and understand the race regulations for each specific event.  As these classes are trying to sit between the extremes in build/tuning limitations, they tend to have a greater number of specific rules than other classes.  However, as a general principle is important to remember the purpose of these classes- to support tuned machines with advanced parts, but without the need for modification.  The many differences in similar mi-level classes are therefore along the line of what counts as “modification.” Reading the rules with this in mind will help greatly.

Box Stock

Box Stock is the most restrictive of all the competition classes and therefore has the simplest requirements for participation.  Racers are limited to what is in the box when they build a kit and modification of any type to any part is prohibited.  This simplicity has earned it the mantle of being the common entry point a racer will have to Mini4WD.  However, mastering the skills required to excel in this class are as difficult as they are fundamental to success in other less restrictive classes.

Variations

There are many more classes designed to create specific challenges for willing racers.  While each class is designed to be distinct, it can be helpful to think of all other classes as being a variation of one of the above. 

Box Stock Variations

Box Stock 5:1

A Box Stock variation that is limited to machines with a 5:1 gear ratio, such as the popular Animal Racer series.  The purpose is to allow these kits to compete with other 5:1 machines in a more family friendly competition class.

Kit Class

Kit Class turns Box Stock into an extended event as racers must first assemble an unopened kit in a limited amount of time.  It is also common for these to be kit specific events, making them a true test of building fundamentals.

Pro Stock

Racers in Pro Stock are allowed to assemble a machine from parts found in any basic kit.  It is still Box Stock, with the provision that you can use multiple boxes to assemble a machine.  This opens the door to basic tuning of rollers, wheel/tires, and gear ratios all while adding an element of fun for those who enjoy a bit of collecting or treasure hunting.

Rat Stock

These ultra-light and, at times, dangerously fragile machines are the pinnacle of what can be done without the use of additional parts.  Rat Stock allows racers to modify their machine’s body and chassis to lighten or redistribute its weight.  It is the proving ground for the notion that tiny changes can matter greatly in a machine’s performance.

B-MAX/Tuned Variations

P-Max/Stock Advanced

Typically built on Tuned or B-MAX rules that limit modifications, these classes further restrict racers to only using plastic parts, such as rollers and bushings for their machines.  HG parts such as bearings, aluminum rollers, and carbon plate are all prohibited.

Stock-EX/Rat Stock-EX

These classes advertise parade as Box Stock but are much closer to Tuned Class. Allowing the use of any part that does not require the use of a vertical screw/pole for mounting (such as traditional mass dampers or high mounted rollers) the resultant machines look stock, but are capable of much faster track times.

Open Variations

High Speed

Using unsanctioned motors and custom extra-large diameter and ultra-thin wheels, these machines typically require special track conditions to run.  They might not be “legal”, but they are the fastest Mini4WD machines on the planet and the epitome of what it means to build a machine from the ground up.