Efficiency often comes down to cadence, so what pedal revolution cadence are you pedaling at?
I think most pedal at around 80-95rpm, above 100 and you're probably a fast twitch muscle build, below 70rpm and either you're just going slow or are pedaling too big of a gear and your knees might not last long.
Cadence times gearing gives you your speed, gear ratios by themselves without a cadence number is only somewhat helpful.
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