We carry an assortment of rear derailleurs for every type of bike, terrain and riding style. Each performs the same basic duty: it moves the chain across the rear sprockets, so you can always be riding in just the right gear. Unless you’re a diehard single-speeder, that’s a pretty magical thing.

Most rear derailleurs share the same basic design, with two pivots (upper and lower) plus a cage and two pulleys for the chain to run through. The derailleur is bolted to the frame via a rear derailleur hanger. Movement of the derailleur is controlled by a handlebar-mounted shifter. The shifter, usually positioned on the right side of the bars, either pulls a cable that moves the derailleur, or, in the case of electronic drivetrains, communicates with the derailleur electronically.

There are a few things to know when shopping for a rear derailleur. We carry dozens of models from top brands like Shimano, SRAM and Campagnolo, so to narrow down your search, start by selecting either road or mountain bike. You should also know how many gears your drivetrain uses. And lastly, you’ll need to choose a cage length. Long-cage derailleurs accommodate a wider gear range and are more common on mountain bikes or other off-road bikes (which may use a single chainring up front), allowing the chain to run across all the gears with a stable chain line. Road bikes typically use short-cage rear derailleurs, which are lighter weight and ideal for lightning-fast shifts across a tighter range of gears.

Many modern mountain bike drivetrains use a clutch rear derailleur, which helps maintain tension in the chain and prevents the derailleur cage from bouncing and causing noisy chain slap on the frame. Both Shimano and SRAM offer clutch type rear derailleurs.

One other variable to consider is electronic versus mechanical. If you have an electronic drivetrain on your bike, your rear derailleur choices will be fairly straightforward, as you’ll need to choose something that’s compatible with the shifters. One thing is certain, your rear derailleur is one of the hardest working components on your bike. Having one that’s well maintained and functioning properly can make or break your ride. If you have any questions at all, hop on a call or a chat with one of our expert Gear Advisors today at 888-880-3811 so that we can help you find that perfect item.