The 48/31T chainring combination on Shimano's GRX FC-RX820-2 reflects a specific philosophy about gravel gearing that differs from the wide-range 1x approach. Where 1x drivetrains prioritize simplicity and range at the expense of gear spacing, this 2x setup maintains the tight steps between gears that road cyclists rely on for cadence control. Paired with an 11-34T or 11-36T cassette, you get 24 gear combinations with minimal redundancy and smooth transitions when the terrain changes. That matters in competitive gravel events and fast group rides where finding exactly the right gear keeps you efficient rather than grinding or spinning awkwardly between available ratios.

The 17-tooth chainring difference spans a useful range for mixed-terrain riding. The 48T outer ring handles fast descents, tailwind sections, and paved road connections where you need top-end speed. The 31T inner ring provides legitimate climbing capability without the massive jumps in cadence that wide-range cassettes create when paired with 1x systems. You still get low gears for steep gravel climbs, but you arrive at them through gradual steps rather than dramatic shifts that disrupt your rhythm.

Hollowtech II construction integrates the bottom bracket spindle with the drive-side crank arm, creating a stiffer assembly that resists flex under hard efforts. The hollow aluminum crank arms reduce weight while maintaining the structural integrity needed for aggressive riding. At 710 grams for the 170mm version, the FC-RX820-2 sits in performance territory for an aluminum 2x crankset. The 47mm chainline works with the FD-RX820 front derailleur's offset cage design to provide clearance for gravel tires up to 40mm or wider depending on your frame.... Read More