Even if the wheels weighed the same. the 14" wheel would spin more easily than a 17" or 18". The distibution of mass is different. Because in the 14" wheel the weigh actually has a shorter path to complete around the axis of rotation. It's like an ice skater they spin the fastest when their arms and legs are tight against their body and and to slow themselves down they put their arms and leg out. So for a rotating mass the smaller the better. Hell find 13" rim for the track, and you'll have another gain.
Sorry if this explanation didn't make sense I haven't had to do physics in a couple years now. If something doesn't make sense let me know I'll try to elaborate

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Michael J. Kulaga
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