Can I use the eTap AXS rear derailleur without the front derailleur to make a 1x drivetrain? May 23, 2019 19:12 Updated Yes. Related articles Is there a different eTap AXS rear derailleur for 2x and 1x drivetrains? What is the max cog size that is compatible with SRAM RED or Force eTap AXS™ rear derailleurs? Is there a WiFLi version of SRAM RED or Force eTap AXS™ rear derailleurs with a higher max cog size? Are 11-speed SRAM RED eTap derailleur batteries compatible with SRAM RED and Force eTap AXS derailleurs? Can RED and Force eTap AXS™ be fitted to a bike that is currently compatible with 8, 9, 10 or 11-speed groupsets?