What is the mechanism located just under the wheel hub that is responsible for changing the rear gears?

The rear derailleur allows you to change the rear set of gears to adjust the resistance of your ride. When shifting gears while riding, the change in tension shifts the chain guide sideways derailing the chain onto another gear. The rear derailleur also is responsible for taking up chain slack.

Asked by Jason Forbes · Last updated 5 years ago · 5.4K views · SOURCE