SRAM X-SYNC Direct Mount Chainring for BOOST

If you have a crankset with a completely removable spider, there’s a pretty good chance you can pull the crank, remove the spider, and install an SRAM X-SYNC Direct Mount Chainring for the ultimate in light weight, simplicity, and strength in single ring applications. These rings mate with right crankarms that have a splined mount and three bolts that secure the chainring onto the splines. As a contrast, Cannondale’s Hollowgram cranks have splines as well, but are secured to the arm via a lockring. X-SYNC refers to the design of the teeth. You may think that single-ring setups just take one ring from a double-ring crank and that you’ll need a chain guide to keep the chain on the ring. With X-SYNC, there’s no need for any secondary retention system because the ring is designed for the chain never to shift off this one ring. The key is a unique tooth profile. The teeth themselves are taller than you’ll find on shiftable chainrings. The tops of these teeth are also squared, rather than triangular. And then SRAM goes farther. The base of the teeth has been engineered to possess mud-clearing recesses. They created a unique wide-narrow alternating tooth pattern which lines up with the inner and outer cage plates on the chain. The tooth pattern synchronizes with the chain. They recommend their standard eleven- and ten-speed chains. The chainring teeth and recesses have been designed with this chain in mind. Chainrings range in size from 26 to 40 teeth. A 26 weighs 61g, while a 40 weighs 119g. SRAM recommends matching the X-SYNC with their XX1, X01, and GX drivetrains, though it certainly can work in other single-ring applications. Here’s where knowing which ring to choose gets a bit tricky. There are two different offsets. There’s a 6mm inboard offset for standard chain lines. There’s a 3mm inboard offset for Boost chain lines. Boost is the 148x12mm rear hub standard, which moves the cassette body 3mm towards the right chainstay. Boost is a new standard, common to 27.5 plus bikes and some other applications. Further, as there are two different bottom bracket spindle standards, there is a second piece of info you’ll need if you’re setting up this Direct Mount chainring on the second standard. The first, btw, is a 24mm spindle diameter, which is SRAM’s standard GXP dimension and most common. The second is a 30mm spindle, which works with a number of oversized bottom brackets, particularly BB30 and PF30. To fit the Direct Mount ring on the 30mm spindle, you also need to measure the drive side spacer to know which offset you’ll need. If you have a 15.46mm spacer, it’s the same thing as with a 24mm spindle: the standard chainline takes a ring with 6mm of offset and Boost with 3mm of offset. If there’s a 9.11mm spacer, the standard chainline works with 0mm of offset, and it is not compatible with the Boost chainline. SRAM’s X-SYN Direct Mount Chainring is the simplest and lightest way to have a 1x crank.