Winning Pinewood Derbies - One Wheel Up

One thing you often see recommended is putting one of the wheels up so that it doesn't run on the track.  The idea is your reducing the amount of friction by going from four wheels to three.  The question is does this work?  So I decided to put it to the test.  I did one wheel up for each trial with one in the front and then one in the back to see if it makes a difference.

As you can see in the tables leaving one wheel up does make a big impact on the performance of the car.  It is interesting that leaving a front wheel up has a larger impact than leaving a back wheel up.  I rationalize it by noting that the center of gravity is towards the rear of the car.  Thus since most of the weight is near the back then having both wheels down helps to distribute the load and keep the car running true.

The final test ran was to alternate which wheel in front was up.  The reason I do this is after I prepare my axles and wheels I give them a spin test.  This is done by holding the axle in one hand and spinning the wheel and then timing, (I just count or you could use a timer), how long the wheel spins.  Longer is better, if is spins more than 30 seconds you are well on your way.  It should spin smoothly and without wobble. I then take the best three pairs, (axle & wheel), and these are the wheels I put down and the slowest one I leave up.  So for this test the slowest wheel is on the left front. As you can see from the last table leaving the slowest front wheel up does produce the best results.


My recommendation it to put the three fastest wheel/axle combinations down and put the slowest one in front and raise it off the track.  However do not raise it to high as it still need to be able to ride the center strip of the track and help keep the car on course.


      Trial (sec)        
Test 1 1 2 3 4 5 Avg STD
All Wheels Down 2.313 2.328 2.310 2.320 2.330 2.320 0.009
Front left Up 2.242 2.258 2.254 2.254 2.255 2.253 0.006
          difference 0.068  
      Trial (sec)        
Test 2 1 2 3 4 5 Avg STD
All Wheels Down 2.482 2.452 2.481 2.476 2.452 2.469 0.015
Back Left Up 2.468 2.46 2.447 x x 2.458 0.011
          difference 0.010  


Test with the slowest wheel/axle combination on the left front of the car.

      Trial (sec)        
Test 1 1 2 3 4 5 Avg STD
All Wheels Down 2.350 2.345 2.351 2.330 2.344 2.344 0.008
Front left Up 2.243 2.245 2.249 2.254 2.286 2.255 0.018
Front Right Up 2.294 2.3 2.303 2.297 2.297 2.298 0.003
          Front Left Difference 0.089  
          Front Right Difference 0.046  

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