Things You'll Need
Very fine-grain sandpaper
The Pinewood Derby is a major event in the lives of many Cub Scouts. Designing, building and painting their cars is an annual tradition that stretches back decades. While the kit contains all the car parts--wood block, wheels, axles and instructions--Cub Scouts must squeeze every bit of performance out of them to win the derby. Since you can't change any of the parts, it is important to know how the parts can be modified. One promising way to improve the speed of the car is to alter the basic wheels that come in the kit.
Wheel Polishing and Coning
Place a wheel on the end of a drill bit. Any bit works as long as the wheel slides on snugly without deforming the hub.
Attach the drill bit and wheel to your power drill. Tighten the bit.
Spin the drill while rubbing the wheel's tread on the sandpaper. You can hold the sandpaper in your hand; the wheel shouldn't spin long enough to heat up. Use a sanding block as an alternative.
Rub the wheel until it is smooth.
Take a little extra off the outside of the tire surface to create a slight cone shape. This minimizes the amount of wheel on the ramp and reduces friction.
Hold a wheel so the outside is facing down.
Poor liquid epoxy into the opening in the middle of the wheel until it is about 3/4 full.
Tap the wheel firmly on a hard surface to make sure the wheel is full and there are no air pockets.
Let the wheels dry for 24 hours.
Test your wheels to make sure they are all the same weight. If not, you can add more epoxy to an underweight wheel, but it probably still won't balance. It is generally easier and faster to start over with another kit and four new wheels.
Make sure you are familiar with your area's Pinewood Derby rules. While these tips are not against the Scouts’ rules, each pack can customize its own rules.