Built for gravel riders who want a clean, uncluttered drivetrain, the Shimano GRX FC-RX820-1 is a 1x12-speed crankset from the top-tier GRX groupset. Hollow-forged aluminium arms keep rotating weight low while delivering the stiffness needed for hard efforts on mixed terrain — whether that's a punchy gravel race or a loaded bikepacking route.

Highlights

• Hollowtech II construction: Hollow-forged aluminium crank arms and integrated spindle reduce weight without sacrificing lateral stiffness, putting more of your power into the drivetrain.
• 1x12-speed simplicity: A single chainring paired with a wide-range 12-speed cassette gives you all the range you need with a lighter, simpler setup and no front derailleur to manage.
• 110mm asymmetric BCD: Shimano's asymmetric four-bolt spider accepts 40T or 42T GRX chainrings, with the potential to run other compatible gravel chainrings as well.
• 49.7mm chainline: Optimised for use with road disc hubs (135/142mm spacing) and designed to clear wide gravel tyres without compromise.
• Five crank arm lengths: Available in 160, 165, 170, 172.5, and 175mm to suit a wide range of rider heights and fit preferences.
• GRX 12-speed ecosystem: Designed to work seamlessly with GRX RD-RX822 rear derailleurs, GRX ST-RX820 shifters, and 12-speed HG chains for a fully integrated gravel drivetrain.

Gravel-First Engineering

The GRX series is Shimano's dedicated gravel platform, and the FC-RX820-1 sits at its mechanical 12-speed peak. The 1x drivetrain format eliminates front shifting complexity, reduces chainline variation, and sheds system weight — all without giving up the gear range modern gravel riding demands. The Hollowtech II outboard bearing system places the bearings wide in the frame shell for improved load distribution and pedalling stability over rough surfaces.

Compatibility & Fit

The FC-RX820-1 is a 12-speed single-chainring crankset requiring a separate Shimano Hollowtech II bottom bracket (such as the SM-BBR60 for threaded shells). Chainring options: 40T or 42T at 110mm asymmetric BCD. Chainline: 49.7mm. Q-factor: 151mm. Compatible with frames using 135mm or 142mm rear spacing and chainstays of 415mm or longer. Pedal threads are standard 9/16". Pair with a GRX RD-RX822-GS or RD-RX822-SGS rear derailleur depending on cassette capacity. Bottom bracket sold separately.