SRAM produces XDR and XD drivers, allowing cassettes to be installed with 11 speeds or less. This is perfect if you want a 1x drivetrain or to equip larger gears. It helps eliminate the possibility of some of us topping out on flats and when descending.

For an explanation, please watch this video first. More information is available below the video.

Do you need SRAM's XD or XDR driver?

If you like getting your mountain bike dirty, you'll end up with an XD driver. The XD driver is the same size as an 8, 9, or 10-speed HyperGlide freehub body. The XDR driver is used for road bikes, cyclocross, gravel bikes, etc. The XDR driver is about 2mm longer than the XD driver and is designed to be the same as an 11-speed HyperGlide freehub body. An easy way to remember the difference is that the "R" stands for road bike. The XDR driver can mount a 10-speed XD cassette by using a 1.85mm spacer.

What is an XD driver?

In 2015, SRAM developed a new XD driver to use 10-speed cassettes. Using 10 speeds allows for a wider gear range on the cassette and enables 1x11 to function similarly to SRAM's double chainring setup. You can also find 9-speed versions from smaller, niche cycling component suppliers. SRAM open-sourced and released XD, so many companies jumped on board and began producing their own XD drivers. This was aided by the fact that XD was designed to work with existing axle designs and ratchet mechanisms. The only major company not involved is Shimano. SRAM also states that XD drivers have advantages over traditional freehubs. Cassettes have reduced wobble and are less likely to damage the body. Freehubs are more stable, and improved bearing durability can be expected.

What is an XDR driver?

XDR is the road bike version of the XD driver mentioned above. It is 1.85mm longer than the XD driver and was designed for 11-speed road bike wheels. Like the XD driver, it offers advantages over traditional freehub bodies, saving about 6-8 grams compared to a standard freehub body. The biggest advantage for XD and XDR drivers is that you don't need to readjust your wheel when changing to a larger cassette. Less time spent working means more time we can all spend enjoying our bikes.