Inverse ... same external gear ratio, smaller wheels the gear inch (as if a big penny farthing bike wheel) is lower .

hence a use of a 16:53 with a 20" wheel.



a 29er wheel needs a lower ratio because the wheel diameter is bigger .

the hub manufacturers decision was to allow a 2.1:1 for 29ers , followed that need .


Of course us old people are not really the ones straining the mechanicals.