Pack 421’s Pinewood Derby Rules

Last revision: December 13, 2020

For build resources, click here.

GENERAL

• The car must be built for the current Pinewood Derby Racing Season.

• No repeats or repaints.

• Complete cars purchased from a third party are not allowed.

• The car may not be sent to a third party facility for tuning or other performance enhancements.

• Each car should be given a name at check-in. Be ready with an awesome name!

body

• The main body structure must be made of wood.

• The car design may be enhanced by the addition of other stable materials such as plastic or metal.

• Any additions must be firmly attached and meet car size specifications. 

• The car must be freewheeling.

The car must meet the following specifications:

• Width: not to exceed 2.75 inches

• Length: not to exceed 7.0 inches

• Height: not to exceed 3 inches

• Weight: not to exceed 5.0 ounces on a scale accurate to 1/10 ounce

IMPORTANT: Car weight is strictly enforced to 1/10th ounce accuracy. It is advantageous to make sure the car weight is as close as possible to 5.0 ounces without going over. If a car exceeds 5.04 ounces at inspection, the Scout will be asked to remove excess weight (using a drill or file if necessary) until the weight is at or below the limit. Note: Most kitchen scales are not accurate enough to measure a derby car properly. Postal scales are more likely to have the required accuracy. Official weight of all cars will be determined by inspectors upon check-in using a single high-accuracy scale to ensure trueness and consistency. Be prepared to make adjustments if needed.

• Weights: The use of lead weight is strongly discouraged. Zinc, tungsten, brass, or other safe materials are recommended instead. If lead is used, it should be completely sealed and not exposed where it could be contacted by children or race officials. Drilling, cutting, or filing of lead (to reduce excess weight) will not be permitted at the venue due to safety reasons. If coins or other loose items are used for weight, make sure they are securely attached (use strong glue, not tape!), and take special care when placing weights on the bottom of the car to avoid creating obstructions that might interfere with the guide rail or braking.

• Clearance: The wheels are the only part of the car allowed to touch the track. Cars roll down the track on a center rail that is 1-5/8 inches wide and 1/4 inch tall. The underside of the car should leave a clear path for the rail and avoid having any protrusions or edges that might catch on the rail (see Car Bottom below). Note: If questions arise about a car’s clearance during check in, race inspectors should place the car on the track to verify that only the wheels touch the track.

• Car bottom: To clear the track rails, the bottom of the car should be no less than 3/8 inch from the surface. However, if the car rolls on the track without touching the rails, the height will be considered legal. Avoid irregular shapes on the bottom of the car. When the car hits the end braking section of the track, it will be sliding on the underbody of the car, not the wheels. If there are notches, grooves, or protrusions, they could cause the car to bounce up and off of the track, possibly injuring itself and/or other Scout’s cars.

• Fenders: Fenders or other body parts may extend below the car bottom on the sides of the body, but remember the guide rail width so the fenders do not rub.

• Wheelbase: You may use the precut axle slots in the BSA pinewood block or make new axle holes for a longer wheelbase. Longer wheel bases promote a more stable car path. Wheels may extend beyond the rear of the car, but may not protrude ahead of the starting pin (front edge of the car). The total car length including the wheels may not exceed 7.0 inches.

• Front Edge of Car: When placed in the starting position, the front edge of the car will rest on a retractable starting pin that protrudes upward from the center of the track. No part of the car (including the front wheels) may extend forward beyond the starting pin. The front edge of the car should be at least 1⁄2 inch wide at the center of the car. This recommendation ensures the car rests securely against the starting pin when placed in the starting position and is wide enough to trigger the electronic timer. A needle nose car will be permitted to race, however its performance will suffer because the nose will not trigger the electronic timer accurately. If you choose to run a needle nose car, the electronic time, even if it is slower than the car’s actual time, will be the official time.

The following items are prohibited:

• Springs

• Magnets

• Starting devices or propellants

• Electronic or lighting devices that make sound or interfere with the race electronics. (Decorative lights that do not interfere with race electronics are permitted. But note that you will not have an opportunity to turn them on or off after check-in. Make sure the battery is turned on prior to check-in and can last through the end of the race.)

• Liquids, wet paint, oil, sticky substance, or powders of any kind (other than axle lubrication)

• Glass or excessively fragile parts

• Wheel/Axle bearings, bushings, and washers

• Loose objects on car

Wheels

Only official BSA wheels are allowed. Official BSA colored wheels (available from Scout Shop and other suppliers) are allowed, but make sure they are official BSA wheels.

• All lettering and numbering on the outside and inside of the wheel must remain complete and visible for inspection.

• The decorative spokes and fluting (small dots) on the outside of the wheel must remain visible and complete around the entire circumference of the wheel.

• The outer tread surface (the flat part that touches the track) may be sanded, shaved, or polished to remove imperfections and to true roundness, but the tread must be flat and parallel to the wheel bore. Therefore, the following modifications are prohibited: Rounding of the tread surface, Grooving, H-cutting, or V-cutting the tread surface.

• The inside edge of the wheel may be trued and smoothed to ensure straightness, but the width of the tread surface must be at least 6.5mm. This rule is only in place to prevent extreme narrowing of the wheel tread width. Wheel tread width will not be measured unless a wheel has been noticeably and significantly narrowed.

• Lathing or removing material from the inner surfaces of the wheel is prohibited. Wheels will be checked for this during inspection. Wheels in violation can easily be detected due to having thinner than normal plastic thickness and/or non-standard machine marks (grooves or step edges) on the inner surfaces. Cars with illegally modified wheels will not be allowed to race in the Pack Championship Series or Open division, but may be entered in the No- Rules division.

• Drilling holes in the sidewall or tread of the wheel is prohibited.

• Wheel bore treatments are allowed, including polishing, waxing, sanding, and/or tapping. However, filling and re-drilling the wheel bore—or narrowing the wheel bore in any other way (e.g., bushings, bearings, etc.)—is prohibited.

• Washers, air shields, and air dams between the wheel and car body are prohibited.

• The inside cavity of the wheel may not be filled with any material except small amounts of fingernail polish for balancing.

• Accent paint on wheels is permitted but should be avoided on contact or friction surfaces. Stickers and decals should not be attached to wheels or axles.

Common legal modifications include, but are not limited, to the following:

• Truing the outer tread surface to correct out-of-round wheels (but do not remove so much tread material that any of the decorative fluting or dots on the sidewall is removed).

• Truing and shaping the inner edge of the tread surface to get smooth straight edges (but do not remove so much edge material that the tread width is reduced to less than 6.5mm).

• Applying wheel bore treatments such as polish and wax to smooth the bore.

• Truing or coning the tip of the inner hub and/or removing the step on the outer hub.

• Balancing the wheel by adding a small amount of material such as fingernail polish to the inside of the wheel.

Number of wheels:

• At least 3 free-spinning wheels must be attached to the sides of the car body using a legal axle.

• An aftermarket guide fin is legal to be used in place of the 4th wheel. You will not have an opportunity to adjust the alignment during the race.

• If you choose to run with 4 wheels, it is not required that all 4 wheels touch the surface of the track.

Pack Championship Series
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