XX1 cranks have carbon arms with a forged aluminum spider. The alloy chainring bolts thread directly into the chainring which lays into the stepped spider for a very solid interface that eliminates the need and weight of chainring nuts. SRAM offers the XX1 crank in two Q-Factors: 156mm or 168mm so you can dial in frame clearance and/or riding position.
The chainrings on most double and triple cranks have to be designed for chain movement which can lead to the dreaded dropped chain (which always seems to happen at the worst time). Since XX1 is a single front chainring system, the chainring can be designed around chain retention.
SRAM engineers looked into the causes of chain drop and video analysis showed side to side movement was the main culprit. They came up with a CNC-machined, wide tooth, narrow tooth pattern which perfectly mates with the XX1 chain for a snug fit. This profile known as X-Sync also features slight taller, squared-off teeth that makes chain drop a virtually non-issue.
From world cup racing to Marathon to downhill, XX1 is taking the mountain bike world by storm for some big reasons. XX1 is about 200 grams lighter than the next lightest cross country group because there is no front derailleur, shifter or front cabling required. Secondly, the chainring is engineered to retain the chain where chainrings on double and triple systems needs chainrings that allow chain movement. Because there is a reduced need to reel in chain slack, the rear derailleur can be designed for faster shifts and quiet performance with chain slap virtually eliminated.Features