The Shimano GRX FC-RX610-1 is a purpose-built 1x12-speed crankset engineered for gravel and mixed-terrain riding. Paired with a 38T narrow-wide chainring, it delivers ultra-low gearing for loaded bikepacking expeditions or technical climbs, and works seamlessly with 10-45T or 10-51T GRX cassettes for a wide range that handles everything from flowy singletrack to sealed roads.

Highlights

• 1x12-speed drivetrain: Clean single-chainring setup eliminates a front derailleur, reducing weight and mechanical complexity on rough terrain.
• 38T narrow-wide chainring: Alternating tooth profile retains the chain under vibration and on rough surfaces without a chain guide.
• Wide gearing range: 38T pairs with 10-45T or 10-51T cassettes for a range that climbs the steepest gravel pitches and keeps up on descents.
• Shimano Hollowtech II spindle: Two-piece hollow crank axle delivers excellent stiffness-to-weight and long-term reliability.
• 110 BCD asymmetric: Shimano asymmetric 4-bolt spider allows future chainring swaps between 38T and 40T options.
• 175mm crank arms: Full pedalling leverage suited to gravel and adventure riding across mixed terrain.

GRX Gravel Engineering

The FC-RX610-1 is part of Shimano's GRX 12-speed mechanical groupset, designed specifically around the demands of gravel cycling. The steel narrow-wide chainring is built for durability over long distances and abrasive conditions, resisting wear that alloy rings can't match. At approximately 812g (175mm / 38T), it balances performance with the robustness required when you're far from a bike shop.

Compatibility & Fit

Compatible with Shimano GRX 12-speed drivetrains. Requires a Shimano Hollowtech II bottom bracket (sold separately) — suitable for road disc frames with 135/142mm rear spacing and chainstays of 415mm or longer. BCD: 110mm (Shimano asymmetric 4-bolt). Chainline: ~49.7mm. Q-factor: 151mm. Chain: Shimano HG 12-speed compatible. Not compatible with 11-speed GRX or road groupsets.