If this wheelset played baseball, it'd certainly be a utility player.
The inclusion of disc brakes on road bikes continues with its momentum and we are beginning to see some excellent, race-worthy road framesets and wheelsets. Component manufacturers are now releasing groups with hydraulic offerings on its top-tier lines, and the new Dura-Ace ST-R9120 and ST-R9170 mark the first time we've seen hydro disc brakes under the Dura-Ace moniker. Naturally, Shimano has expanded its wheel offerings, embracing discs and drawing heavily from its mountain bike development along with its proven road technology. The wheelset that we are most excited about is the Tubeless Dura-Ace 9170 C40 Carbon Disc Brake Road Wheelset as it pairs our two favorite revelations in road bike tech over the past few seasons, tubeless tires and road disc.
Disc brakes have numerous advantages on the road and one of the biggest ones we can think of right off the bat is the ability to run wider rubber. By repositioning the calipers closer to the hubs, the fork crown as well as seatstay and chainstay clearance increases allowing for more room for big tires. Of course, as the rubber gets bigger, rims need to increase their width too, to better support the sidewalls and allow for a better tire/rim profile for improved aerodynamics. These rims' external width sit at 24mm wide which Shimano recommends pairing with tires in the 23-32mm range for maximum aerodynamics. The lower rolling resistance and greater ride comfort are quickly appreciated over rougher roads as you take on your own classics.
The depth of these full-carbon rims places it as a perfect all-arounder, perfectly suited to the puncheur or rouleur who needs a lightweight and stiff wheelset for repeated sharp attacks on steep cols and bergs as well as nabbing a sprint in a small select group at the end of a 5-hour slugfest. Its depth offers increased lateral rigidity and gives it enough aero benefit to help that attack stick if that's 30k from the line or a late race surprise inside the flame rouge. Shimano offers a deeper wheel at 60mm for even more aero benefit, but for most riders, we feel this wheelset, at 37mm deep, add enough of an aero benefit without losing stability in windy conditions.
Shimano engineers considered both frontal and crosswind forces when developing the rim's profile. Through prototype testing, both in the wind-tunnel and on the road yielded a wide rim shape with a deep tire bed as the best performer across a wider range of conditions. This shape, known as D2, reduced drag better than previous versions and competitor's profiles at yaw angles ranging from 0 to 15-degrees. An added bonus of the rim's profile is its improved vertical compliance for increased control and comfort over rougher roads. Helping bolster the aero benefits, even more, Shimano uses bladed spokes and places the spoke nipples internally which makes truing the wheels a little more of tricky, but given these wheels' track record on the WorldTour circuit, we don't see ourselves having to do that very often, if at all.
Shimano relies on 24 spokes on the front and rear to handle power transmission and braking forces. The rear wheel sees its OptBal spoke system featuring 16 spokes on the drive side and 8 on the non-drive side. As freehub spacing for the fitment of a cassette causes uneven tension (almost twice as high on the drive side) between sides, by placing fewer spokes on the non-drive side, it requires higher tension, thus helping to balance the overall tension relative to both sides. High and low tensions have a tendency of creating broken or loose spokes affecting durability and strength. The OptBal design rebalances spoke tension improving rigidity and strength for more durability.
The hubs are designed for the centerlock standard offering easy rotor install with its spline mounting interface and a lock ring. In our experience, it's not only quicker and easier to install, it improves the rigidity of the rotor, improving the overall braking performance. Both hubs are designed for 12mm thru-axles which Shimano refers to as E-Thru. While thru-axles help with torsional rigidity and we can't imagine riding a disc brake bike without the additional security it provides, it'd be a shame if we lost any of the tech that Shimano bestows on its quick-release hubs. Luckily, it doesn't and we still get flanges set as wide as possible for the best lateral stiffness. Another favorite Shimano hub feature is the angular contact cup and cone style bearings. It offers greater strength than sealed cartridge bearings as it can displace both lateral and vertical loads more effectively for the smoothest rolling and enhanced durability. This setup also allows for easier, user-friendly maintenance and adjustability.
These wheels tip the scale at 721g for the front, 865g for the rear.
- A versatile wheelset that's tubeless and disc ready
- D2 carbon rim profile improves aerodynamics across more yaw angles
- Rim depth pairs aerodynamic speed and confident stability
- OptBal spoke system better balances rear spoke tensions
- Wider rim width is optimized for 23-32mm tires
- Tubeless compatibility lets you lower tire pressure
- Dura-Ace hubs with cup and cone bearings roll smooth and fast