Enlarge / Haven Mercer’s prototype front assembly for an automatic bike transmission. (credit: Haven Mercer)

Depending on how you look at it, either a lot or not very much has changed about the way bikes shift gears since the mid-19th century.

A lot has been refined along the transmission path, in which your feet push cranks, those cranks turn a big gear, and a chain connects that big gear to a smaller gear on the rear wheel. Shifting has picked up lots of improvements, be they electronic or wireless, as have derailleurs and internal gearboxes. Materials and tolerances have only improved over the decades.

But in almost all cases, you’re still manually adjusting something to move the chain and change gears, depending on the resistance you’re feeling on the bike. Even the most outlandish recent ideas still involve indexed movement between different-sized gears.