Long and Short Cage Derailleurs Explained: What are GS and SGS?

In the mountain bike industry, there is less worry about long vs. short cage derailleurs thanks to the popularity of 1X drivetrains and the extinction of the front derailleur. However, the problem hasn't been solved entirely. Reddit, various forums, and comment sections are still trying to figure out the advantages of short versus long cage rear derailleurs and whether or not they will be compatible with their current cassettes.

While SRAM , TRP , and many gravel and road groupsets are moving to 1X options, the questions remain. Shimano still offers mountain bike rear derailleurs in two sizes and even provides a 2x12-speed drivetrain with its XT and XTR components. So why would you ever need a short cage derailleur?

MTB Short Cage vs. Long Cage Derailleurs

Thankfully, you won't need to learn the difference if you are using a modern SRAM 1X drivetrain, as it only offers one cage length across the entire range. But if you are a Shimano enjoyer, you have likely been bamboozled by the SGS and GS options, but what is the difference?

Shimano uses the designation "SGS" to signify a long cage rear derailleur, which will be the most common in the modern age of 1x12 drivetrains with the widest range. An SGS rear derailleur will accommodate a 10-51t cassette.

GS will signify that the rear derailleur is only compatible with a 10-45t cassette, which will most likely be a rare requirement for most riders looking to replace the original derailleur or purchase an upgraded component. Why would you want the shorter cage, though? A short cage rear derailleur will offer more ground clearance if you ride somewhere with a lot of rocks and tech that can often grab and destroy the lower-hanging long cage options. The Shimano website states that the GS rear derailleur has "greater ground (28mm more than SGS) clearance and supports aggressive riding."

Which Derailleur Do You Need?

To answer this question, first, you need to know what cassette you want to use. Is it the full range 10-51t, or are you looking for tighter gearing and wish to use the 10-45 option?

A longer cage is likely necessary if you want to utilize the full range of modern 1X drivetrains, and it is only a select few recreational riders and high-level racers who are looking for shorter cage options these days.

Thankfully, this will likely not be a common conundrum in the world of mountain biking for much longer as 1X groups are proving to be the preferred choice for everyone, and there is no reason not to go after the most range possible.

Outside of MTB

If you are looking for an answer for the gravel bike, then the same problem still exists, but it seems to be much more clear cut, with SRAM offering the XPLR options for their long cage components and 1X being the industry norm for gravel at this point. If you are a 2X stalwart like myself for gravel and road bikes, Shimano has a similar breakdown for their GRX groupsets and drivetrains, and there is a clear distinction between which rear derailleur is intended for what cassette and crankset option.

The GRX ( RD-RX822-SGS ) SGS option is the mechanical rear derailleur designed for 1x12 drop bar drivetrains with a 10-51 cassette, and the GS ( RD-RX822-GS ) is designed for the shorter 10-45 cassette configuration.