The Shimano GRX FC-RX610-1 38T chainring is the official replacement part for 12-speed single chainring cranksets from the GRX RX610 range, designed for gravel and demanding mixed terrain. With its 110 mm asymmetric BCD 4-arm design and Thick-Thin tooth profile, this chainring guarantees exemplary chain retention, even on the most technical and muddy trails.

Technical Highlights

• 38T tooth count for versatile gearing: the 38-tooth chainring offers the perfect compromise between speed on asphalt and low gearing on rough trails, to be paired with a 10-45T or 10-51T cassette according to your needs (close intervals or ultra-wide range).
• Optimized Thick-Thin profile: the alternating wide/narrow tooth geometry ensures maximum chain retention and reduces the risk of derailment on rough terrain, without the need for an additional chain guide in most configurations.
• Dynamic Chain Engagement technology: special Shimano tooth shape to improve chain engagement, reduce wear and guarantee smooth, silent pedaling, even in extreme conditions.
• High-strength painted steel construction: unlike aluminum chainrings, steel ensures increased longevity against abrasion, impacts and repeated stresses of off-road pedaling.
• Extended compatibility: designed for the GRX FC-RX610-1, this chainring also installs on the FC-RX600 (11-speed) with reservation, and works perfectly with higher-end RX820 cranksets sharing the same BCD.

Standards and System Compatibility

• 110 mm asymmetric BCD with 4 arms: Shimano GRX 12-speed standard, fastened by 4 M8 x 8.5 mm bolts (not supplied).
• 50 mm chainline: identical to original Shimano GRX specifications for perfect alignment with 12-speed cassettes and RX810/RX812 derailleurs.
• Required chain: Shimano 12-speed Hyperglide+ (HG+) chain to take full advantage of the tooth profile and Dynamic Chain Engagement technology.
• Recommended cassettes: Shimano CS-M7100-12 in 10-45T for close spacing oriented toward speed, or 10-51T for ultra-wide range favoring steep climbs and adventure routes.

Available Variants

• 38T variant (current): Ref. Y0SR9801T / EAN 4550170293475 — intermediate ratio, ideal for mixed gravel/fast road use.
• 40T variant: Ref. Y0SR9802T — for faster or rolling routes, offering slightly higher gearing while maintaining the same technology and compatibility.

Real-World Performance

The GRX 38T chainring shines on long-distance gravel rides alternating between paved sections and rough sectors. Its Thick-Thin profile virtually eliminates any risk of chain drop, including on technical singletrack or when clearing obstacles. The steel construction guarantees thousands of kilometers without premature wear, while compatibility with 10-45T or 10-51T cassettes allows fine-tuning of the drivetrain to your terrain and skill level.

Installation and Maintenance

Official Shimano replacement part supplied without hardware (use original M8 x 8.5 mm bolts from crankset). Simple installation by removing the old chainring, cleaning the contact surface, applying a thread of degreaser to the bolts, then cross-pattern tightening to recommended torque. Check alignment and cleanliness of the Hyperglide+ 12-speed chain to preserve the lifespan of the chainring and the rest of the drivetrain.