How to Check the Roundness of Your Pinewood Derby Car Wheels
Pinewood Derby Wheel Concentricity Gage
To check the concentricity of a wheel, slide the wheel on the pin with the spoke side of the wheel facing to the left. The gage pin should ride on the center area of the wheel tread.
Depending on the diameter of your wheel you may need to zero the gage. To do this, loosen the indicator set screw with the provided allen wrench and lightly tighten the screw so you can move the indicator up and down with light pressure on the set screw. Adjust the indicator up or down until the indicator hand reads zero. Lightly tighten the indicator set screw.
The indicator reads .001 inches per division. Rotate the wheel one turn and record the high and low reading on the indicator. For example, if the indicator reads –2 divisions and plus one division then the wheel is out of round by .003. The ultimate goal is zero reading movement as you rotate the wheel. The more a wheel is out of round, the more the wheel will bounce as it rolls.
If you have access to extra wheels, use the gage to find four wheels with the least amount of deviation.
Or, you can round your wheels by using our Wheel Shaver tool.