When it comes to rolling out new gravel offerings, Shimano has taken their component evolution in steps. Following the release of their gravel-specific GRX drivetrain two years ago, it seems the last piece of the puzzle is finally getting rolled out—a carbon wheelset. Curiously, in the time since the GRX was launched, both their road-specific Dura-Ace and Ultegra lines now enjoy a 12-speed upgrade, but the gravel-specific GRX is still only 11-speed (and even 10-speed) compatible. The new RX870-TL wheelset is Shimano’s modern take on a carbon gravel wheel that still plays well across their entire drivetrain line.
With valves and tubeless tape added, the new carbon GRX wheels hit our scales at 1484 grams to be exact (656 grams front and 828 grams rear). The external rim profile is symmetric with a 32mm depth. The external width
is 30.8mm with a 25.2mm internal width that uses a hooked bead and tubeless design.
There are 24 spokes front and rear laced to alloy Shimano hubs that utilize a cup-and-cone ball bearing, as well as Centerlock brake-rotor mount. It seems that Shimano only offers the rear wheel with their HG freehub, reducing its compatibility with SRAM and Campagnolo drivetrains. The rear hub has 18 points of engagement, which is 20 degrees. Shimano says they have optimized the wheelset for 32–50mm tires, and that it will work with tube-type tires too. There is a max pressure rating of 72 psi for all tire types.
Setting up the GRX wheels was a breeze; all of the tubeless tires we tested seated on the rim with ease. The tubeless tires do snap into the bead bed and hold well, even when pressure is too low. For us, this is a big plus and makes fixing a puncture with a tire plug quick, easy and without having to re-seat the bead.
The hooked rim profile was a bit of a surprise in a modern carbon rim designed specifically for gravel. With that said, Shimano isn’t known for leading the wheel-trend category, and with a hook, they can accommodate a wider range of tires and inevitably riders less willing to adopt tubeless.
Since the wheels use a cup-and-cone ball bearing, consumers can adjust bearing tension, but it is not recommended unless you know what you are doing and when to do it. Throughout our testing we didn’t need to make any adjustments to bearing tension. Still, we were surprised that Shimano chose this design for a gravel wheel over a cartridge bearing, which normally has better sealing characteristics.
Gravel-specific or not, when it came to hitting the road, the GRX wheels were great. They seem to offer a bit of vertical compliance but hold solid through corners. We didn’t have too many hard hits to the rim bead, but it seems to be holding up fine from the durability ride we did with the tire pressure too low. At almost 1500 grams, the GRX wheels are well built, and we might even say they swing over their weight category when it comes to durability.
Compatibility is where the GRX wheels fall short. Currently, Shimano only offers the wheels with their HG freehub, meaning SRAM and Campy users will not be able to use these wheels on their drivetrains unless they can find a cassette that matches. SRAM does offer a few options, but they don’t feature their 10t cog, so top-end speed is compromised. In reality, we don’t see consumers wanting to mix Shimano-branded wheels with SRAM- or Campy-branded drivetrains; there are just so many other options on the market.
At the end of the day, Shimano has delivered a carbon gravel wheel that we think could also be a solid choice for road riders, too. For more road-oriented riders, 28mm is the smallest tire we would recommend, but for a rider weighing over 250 pounds, they might need to bump up to a 30mm tire to stay under the max pressure rating. The 72-psi max rating also follows in line with what we have been saying for years now: you simply should not run a modern tire (tube or tubeless) over 75 psi. For most gravel tires you won’t ever exceed 50 psi, even when running a 35mm tire.
The bottom line is that these wheels are a true value at just $1400 for the set. With the value does come some drawbacks, and the biggest in the performance category is the 20-degree engagement. Gravel riders who do a lot of technical riding and are on and off the power a lot will wish they had more than 18 points of engagement. The other drawback that we can see is the potential risk of bearing contamination from the cup-and-cone design. It hasn’t been an issue during our testing, but from our experience, as opposed to sealed bearings, it can be more common.
Overall, Shimano is setting themselves up to launch more gravel components, likely following the road market and adding another speed to the cassette. If they do, it doesn’t look like they will be changing their theories on gear ratios and will remain with the 11t being their tallest cog gear. Only time will tell.
• Great value
• No SRAM or Campy hub body
• Solid construction
Weight: 1484 grams, 656 grams front, 828 grams rear