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Gravity Car Wheel Size

I have built several adult soapbox derby/ Gravity cars. I'm working on a new build that may require a smaller front tire, such as a 16inch tire.

My plan is to run 2 26inch rear wheels and 1 16 inch front  wheel, with a total car weight of 225lbs.   Since there is no gearing, just gravity, and just considering size, will smaller front wheel effect my speed?


Thank you



JM19992 years ago

Make sure you use good bearings on the hubs!

When I coast my bicycle down a hill my 27" wheels act as more effective flywheels than the 26" wheels of anyone coasting beside me. This results in my rolling faster when nothing but gravity is propelling us. Larger diameter wheels take longer to come up to speed, but have a greater top speed than smaller diameter ones. There is certainly some way to calculate the optimum ratio of velocity to top speed for a hill of any given length and grade. This calculation must acquire an added dimension when multiple wheels are spinning, and yet another added dimension when those wheels are varying sizes.