SRAM's rear hub can be adapted for standard quick release or a 142/12-millimeter through axle by simply interchanging endcaps. We asked SRAM to walk us through the 142/12 version. Begin by sliding the rear axle from the hub.
Pull off the endcaps and the XD driver can be slid off the hub's stub axle. The pawls will fall off the XD's ratchet mech, so watch out for loose parts. The ratchet ring and stub axle are shown on the left. SRAM uses oil instead of grease to lubricate the ratchet to maintain operation in freezing conditions. The protruding axle sleeve supports the outboard bearing of the XD driver.
A look at the XD driver's three-pawl ratchet shows the stiff, flat springs and the unique, three-tooth engagement on each pawl. Threads on the driver (right) engage a sleeve inside the eleven-speed cassette. The driver has two sealed bearings. The outboard bearing protrudes about four millimeters and indexes the driver into a sleeve beneath the cassette's smallest cogs.
The black-anodized sleeve can be seen inside the XD eleven-speed X-Dome cassette. Normally, the XD driver will be installed on the hub's stub shaft before the cassette is installed, but we wanted to show how the driver fits into the cassette (right). Like the X.0 cassette, all pedaling loads are carried by the splines of the largest cog. In the case of the XD drive, however, the larger indexing spline that is used on conventional freehubs has been eliminated, because the remaining ten cogs are machined from a single piece of stainless steel and it is not necessary.
A close-up look at the X-Dome cassette(left) reveals the black-anodized splines of its inner sleeve. The cassette simply spins onto the threads of the XD driver using a Shimano-type freehub lock-ring tool. The XD driver's outboard bearing is visible inside the cassette. In real life, you'll need to install the driver first (right). Slide the XD driver over the axle stub and then turn it counter-clockwise to engage the ratchet. The endcap then snaps onto the axle stub.