ajax bay the biggest cog on the rear is the 1st gear and the smallest cog is your highest gear
A 'cog' is not a gear. A combination of the large(st) chainring and the smallest sprocket affords one the longest and highest gear. A combination of the small(est) chainring and the largest sprocket affords one the shortest and lowest gear (for climbing).
Bottom cog? 1st gear? AASHTA
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Gear Numbering
People often want to number their gears sequentially, and will sometimes speak of "7th gear" or "13 th gear." There is, however no standardized way to designate gears in sequence by a single number. If you wish to give your bike's gears sequence numbers, that's fine, but don't expect to be able to communicate with anybody else using those numbers."