National USRA Technical Rules

All cars/racers are expected to comply with these guidelines. All drivers are responsible for the legality of their equipment. There is one car per driver per class, and one driver per car per class. ANY RULE THAT IS IN QUESTION OR BEING INTERPRETED IMPROPERLY WILL BE CLARIFIED BY THE NATIONAL DIRECTOR AND/OR RULES COMMITTEE.


The size of scale to which the cars must be built is 1/24th that of the actual race car


All cars may not be more than 3.25 inches (82.55mm) wide at any point. Round head body mounting pins may extend beyond this width. Other type body pins such as glass head or type are not allowed.


All cars must have front and rear wheels (2 each) with rubber tires.

A. Rear tire minimum diameter is .0750 inches (19.05 mm), unless otherwise specified. Rear wheels maximum width is . 8 10 inches (20.57mm), unless otherwise specified

B. Front tire minimum diameter is .0500 inches (1 2.7 mm), unless otherwise specified.

C. Front wheels or one piece wheel/tire units, must rotate on their axles.

D. Front wheels must be mounted so as to contact the racing surface, as the car is rocked to the side, before grounding on the chassis or body.


The minimum clearance for all classes (except Eurosport) chassis, gear, and motor is .062 inches (1.587 mm). No parts may drag. Guide flag/braid, front and rear tires are exempt from this rule.


One guide or pickup device per car.


Designs should resemble full size race cars. Manufacturers are urged to maintain scale proportions. Variations are allowed to conform to state-of-the-art practices.

A. Paint - All bodies must be fully painted and opaque when sitting on the tech block. The sides of the body may remain clear. They should be detailed to resemble full size race cars. Exhaust pipes, body lines, injector stacks, mirrors and decals are optional.

B. Numbers - All cars must display three numbers of reasonable size and position, 1/4" minimum.

C. Interior - All cars must contain a suitably painted, 1/24th scale, three dimensional driver with helmet, shoulders, arms and steering wheel mounted in the original cockpit position at all times during the racing. No paper drivers are permitted.

D. Windshield - Windshield must be clear and of original body.

E. Wheel wells - Wheel wells must be transparent, or cut to the horizontal center line of the front wheel so when viewed from either side of the car. 75% of both of the front wheel must visible through the wheelwell.

F. Body openings - The chassis must be completely covered by the body and air control when viewed from above, except for the cockpit opening or USRA legal body openings (such as accurate representations of vents, scoops, etc.)


A. No part may exceed 2.5 inches (63.5mm) inches, measured from the tech block surface. Any air control devices cannot be opaque.

B. Side Dams may be a maximum of 2.5 inches (63.5mm) high behind the rear wheel center line and continue on a taper making them a maximum of 2.0 inches (50.8mm) high at a point 3.75 inches (95.25 mm) forward of the real wheel center line. The same taper may continue ahead of the front wheels.

C. Must have the front edges taped and must have outside corners rounded in a manner suitable to avoid injury to race participants and spectators.

D. May affix any decals or markings on any air control surface but cannot be opaque.

E. Diaplane Maximum length is .500 inches (12.7mm) Corners must be rounded.

F. Rear spoiler cannot be opaque, although suitable decals may be affixed.


Any component may be replaced during competition except the original chassis or body. Any racer found to have switched chassis or body will be disqualified immediately. All replacement parts must conform to the rules of the class.



1. Any armature that has been purposely altered or tampered with, to make the stack appear longer, so as to attempt to comply with the length rules as listed, shall be declared illegal at the tech inspector discretion. Stack length minimums shall be required on all 3 poles of the armature (using calipers with the faces across each end of the pole) and only the actual lamination material shall be used to determine this figure. This is meant to specifically exclude, as an example, such practices as the insertion of spacer type materials between the laminations, abnormally thick applications of tings or any methods of artificial compliance with the rule.

2. Any armature presented for tech inspection that is found to be illegal for competition (such as short stack) will be impounded until the completion of the racing class.


Any controller / choke may be used as long as the controller / choke uses no batteries or additional power sources to increase or regulate voltage or amperage at track braid. Specifically prohibited are voltage multipliers or doublers, transformers, batteries, encapsulated components, and capacitors. Specifically allowed are simple wire chokes, and diodes. These lower power but, do not regulate. A variable choke operated by the driver shall not be considered regulated. Relays if used must be powered by the track current only. Controllers / chokes are subject to inspection by USRA officials to verify compliance with the above rules. The Ruddock DR-40 is approved for USRA use.