Aut cum scuto aut in scuto
Wrinklewalls....clever solution to providing a lower gear ratio at the start, the centrifugal force at higher RPM expands the diameter making the "ratio" higher. Shortening the sidewall also bows the tread surface out slightly to ensure full gtread contact for better traction. Expensive, but effective way to make a "variable speed transmission."
MAYBE one more notch on the clutch?