The Dura-Ace R9170 C40 Disc wheelset is Shimano's premier offering in a carbon rim disc wheelset built with a 37mm rim height for all-around riding conditions. The beautiful satin finished carbon rims have the Shimano D2 rim profile to improve aerodynamics across a wide variety of yaw angles, making the wheel seem slippery in all conditions including cross and quartering winds. The rims feature tubeless compatibility and are fixed to a pair of Dura-Ace C40 specific hubs with forged straight pull spokes. The standard thru axles design with modern rim profile and width makes the C40 Disc an excellent choice for any contemporary disc frameset.

One of the best parts of owning a Dura-Ace wheelset is the hubset. The R9170 hubs feature Shimano's familiar wide flange and bearing spacing, as well as the proven CBN finish cup and cone system, which features contact seals that have premium stainless steel bearings. The fully serviceable hubs have a titanium freehub body which saves weight, but also resists wear from the constant force and torque applied by the cassette. The titanium composition is harder than the cassette, so you will not see the scoring and excessive wear that occurs with aluminum freehub bodies. As with all Dura-Ace hubs, engagement is rapid, smooth and quiet. The stiff machined aluminum hub shell uses an oversized and hollow alloy axle, as well as reinforced spoke flanges for optimal strength and to help reduce flex.

The 24 spoke C40 wheels use straight pull spokes coming directly off the reinforced hub flange which allows for high tension build quality. While the front wheel uses a standard 24 hole radial lace design, the rear uses Shimano's OPTBAL spoke system, that feature a total of 8 spokes on the non-drive side and 16 spokes on the drive side (for a grand total of 24). Building the rear wheel in this manner helps to balance and regulate the tension on both drive and non-drive sides of the wheels, effectively balancing the load put on the wheel from the torque of the drivetrain. The net effect of OPTBAL is a very stable and strong wheel that holds high tension, but is resilient enough to have a smooth ride quality.