Properly prepared wheels and axles, along with weighting, are where the majority of speed gains lie in a Pinewood Derby® car. As a result, League racers spend most of their time working on the wheels and axles.
Official Pinewood Derby® wheels leave much to be desired and need a fair amount of work to maximize their potential. The kits’ wheels will have imperfections, such as rough areas, runout (high and low spots on the tread), etc. This chapter will focus on fixing these imperfections and maximizing the wheel’s speed potential!
PRO RACER TIP FROM HurriCrane Racing: If your rules do not prohibit modified/lightened wheels, use them!
Stock vs. Modified wheels - Modified and lightened wheels significantly boost speed. Lighter wheels have a lower inertia coefficient. As a result, they begin rolling sooner and take less energy to start rolling than stock wheels. These lighter wheels translate into a faster start for the car and savings in energy that can be used to propel the car down the track! Additionally, these wheels experience less aerodynamic drag. Modified wheels are available for purchase here!
Modified wheels are lighter and have reduced contact points with the axle, car body, and track. As a result, these wheels decrease friction, drag, and rolling inertia, resulting in a much faster car!
Both modified and unmodified wheels have five areas that need to be polished. They are: Tread, Tread Edge, Outer Hub, Inner Hub, and Axle Bore (hole).
To maximize wheel speed you will need a few supplies and tools:
• Handheld power drill • Method to hold the wheels in the drill
• High grit (1000) sandpaper • Plastic polish
• Cotton swabs (Qtips™) • Dish soap with a small bowl
• Microfiber cloth • Wax (synthetic automotive wax will work)
• Paper towel or cotton cloth • Fuzzy pipe cleaners
Optionally there are kits designed explicitly for this purpose and contain everything you need to create professional, league-quality wheels!
You will need a method to hold the wheels in the drill so they can be spun and polished. As of the writing of this book, the paper stalk of Target® brand cotton swabs will fit tightly into the BSA wheel bore. Cut off both ends and carefully insert the stalk into the wheel. There should be enough friction to hold the wheel while spinning to polish it. Alternatively, there are tools designed specifically for this purpose and are the preferred method for many league and Scout/Youth racers.
Using your preferred method for holding the wheel in the drill, follow these steps:
STEP 1: Start with the wheel’s tread edge. When using wheels straight from the kit, there can be flashing on the wheel from the manufacturing process. Use the high grit (1000) sandpaper to sand the edge of the wheel while spinning it with the drill. Do not over-sand; you want to sand just enough to remove the flashing. With modified wheels, you’ll want to sand off any burs from the cutting process but don’t round over the edge. Next, use a wet paper towel or cloth to clean any plastic and sandpaper particles from the wheel. This is the only step utilizing sandpaper on the wheels.
PRO RACER TIP FROM Reece Racing: Don’t sand your wheels aggressively with multiple grits of sandpaper. Every hand drill and most drill presses have a fair amount of runout (wobble) in their chuck. You’ll sand this runout INTO the wheels, something you want to avoid. Instead, use polish to prepare the wheels.
STEP 2: Apply a small amount of polish to the microfiber cloth (or use a cotton swab). Spin the wheel, using light pressure, polish the tread edge with the microfiber/polish for 1-2 minutes. Use a wet paper towel, cotton cloth, or soft bristle toothbrush to clean any remaining polish on the wheel. BE CAREFUL with the cloth near the spinning drill as it can become entangled with the drill chuck, and pull fingers in with it. Cutting the microfiber or cotton cloth into smaller pieces or using a cotton swab can help reduce this risk.
The target RPM for each polishing step is around 600; adjust the time accordingly if your chosen tool is slower or faster than this.
STEP 3: Repeat Step 2 on the inner hub for 1-2 minutes with the microfiber (or cotton swab) and polish. Use a wet paper towel, cotton cloth, or soft bristle toothbrush to clean any remaining polish off the wheel. You can also rinse in a sink to remove the polish.
Inspect the tread edge and inner hub, ensuring the surfaces are smooth with no remaining flashing/burs and the plastic is shiny. A magnifying glass or jeweler’s loupe is a handy tool for wheel inspection. If you feel the plastic is not quite shiny enough, repeat the polishing steps, but do so in 30-second intervals.
STEP 4: Turn the wheel around to polish the tread. Apply a small amount of polish to the microfiber cloth (or cotton cloth). Spin the wheel, using light pressure polish the tread with the microfiber/polish for 1 minute. Use a wet paper towel, cotton cloth, or soft bristle toothbrush to clean any remaining polish off the wheel. You want the wheel treads to be smooth but NOT slippery, so don’t overdo polishing the wheel tread.
STEP 5: Apply a small amount of polish to a cotton swab. While spinning the wheel, use medium pressure to polish the outer hub. If using stock wheels from the kit, you’ll want to concentrate on the outer step. Polish for 1-2 minutes adding polish every 30 seconds. Use a wet paper towel, cotton cloth, or soft bristle toothbrush to clean off any remaining polish on the wheel. Next, inspect the hub making sure it is smooth and shiny. A magnifying glass or jeweler’s loupe is a handy tool for this. If you feel the plastic is not quite shiny enough, repeat the polishing steps, but do so in 30-second intervals.
STEP 6: Remove the wheel from the drill. It is now time to polish the bore. A Target® brand cotton swab stalk works for this step. Or, bore polishing tools are available in the wheel polishing kit and are the preferred method of professional league racers. If using the swab stalk, ensure the seam on the stalk is oriented so it runs with the direction of rotation when spinning. Apply polish to the swab stalk or polishing implement from the kit. Spin the drill as slow as it will go. Insert into the wheel from the front and move the wheel forward and back slowly for 15-20 seconds. Remove the wheel, add more polish, flip the wheel and polish the bore for another 15-20 seconds. Rinse the bore in a sink with warm water. Inspect the bore making sure it is smooth and shiny. A magnifying glass or jeweler’s loupe is a handy tool for this. Hold the wheel toward a light so you can see in the bore. If you feel the plastic is not quite shiny enough, repeat the polishing steps, but do so in 10-second intervals. Remember, you want to spin the drill slowly when polishing the bores.
PRO RACER TIP FROM JBD Racing: When polishing the bores, it is IMPORTANT to run the drill SLOWLY. Too much speed will enlarge or deform the bore, making the car more likely to wiggle and significantly affect performance.
Once you have polished all critical surfaces, soak the wheels in a mixture of warm water and dish soap for 5 minutes. Soaking the wheels will help remove any residue from the polish. Next, rinse the wheels thoroughly to remove all traces of the soap.
Pinewood Derby® Wheel Preparation - Waxing/Sealing the Wheels
After polishing and cleaning the wheels, it is time to seal the polished surfaces. Synthetic car wax will work, though there are sealer/wax blends formulated and tested specifically for this purpose, and they are the preferred choice by league racers.
Using a cotton swab or applicator from the kit, apply wax to each polished surface, excluding the treads. Use the applicator from the kit or a pipe cleaner for the bore. If using a pipe cleaner, be careful when inserting it into the wheel, so the metal wire does not scratch the bore. Allow the wax/sealer to dry, and then buff off using a microfiber cloth or cotton swab. For the bore, use a new pipe cleaner to buff, or if purchasing the kit, there is a special tool and technique that does an excellent job of buffing the bore and is a step where younger members of the Race Team can fully participate! Make sure to remove any excess wax/sealer. If sealer builds up in the wheel spokes, use a soft bristle toothbrush (dry, no water) to clean the wheel once the wax has cured. Multiple coats of wax (2-4) can help add additional speed!
Do a final inspection of the wheels for any polish/wax residue or lint from the polishing cloth, cotton swabs, or pipe cleaners. Any foreign material trapped on the polished surfaces can reduce speed.
PRO RACER TIP FROM Mojo Racing: Be careful when handling the wheels, especially once they’re polished and sealed/waxed. They can be slippery, and dropping them on the floor can very easily lead to a chipped edge and slower speed! When working on the wheels, lay a towel on the work surface so a dropped wheel won’t roll off the table!
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