It looks like gravel wheels are about to get even wider. The new Reserve 40|44 GR wheels are 27.4mm/27.mm wide. That’s the internal width, not external. That makes them wider than some current XC mountain bike wheels, though that kinda makes sense with how gravel bikes are being ridden these days.
Reserve states that the added width allows the rims to accommodate tires up to 50mm wide, with the recommended tire range listed as 30-50mm in width.
More than just being super wide, the 40|44 GR claims to be super aero as well. While Reserve was founded by Santa Cruz Bicycles in 2014, they’ve gradually made their way from MTB, to gravel, to Pro Tour road racing with Team Jumbo Visma in 2022. Given that Santa Cruz / Reserve and Cervelo are now both owned by PON, the collaboration makes sense and it has allowed the two very unique brands to work on a unifying project – aerodynamics.
Using what they call “exclusive Turbulent Aero wind tunnel testing,” the Reserve 40|44 GR shape was validated with simulated real-world airflow. They go into more detail here, but it seems that the wind tunnel can create turbulence that you would typically only see in a real-world environment, which helped them create a rim profile that is fast in the real world, not just in the wind tunnel.
The result is a wheelset with slightly different profiles. The front is a 40mm depth with a 27.2mm internal width, while the rear is a bit taller and narrower at 44mm deep and 27mm internal. Externally, the rims measure 36/34.4mm wide, and both run 24 straight pull spokes. Those spoke holes are internally reinforced to resist pull-out with specifically engineered carbon plies that Reserve has developed over years of building carbon rims for mountain bikes.
Rather than use a hookless design, Reserve uses what they are calling “semi-hooked”. There is a definite lip around the edge of the rim, and it allows the rims to offer an 80 psi maximum pressure which seems pretty high for a rim this wide meant for gravel bikes.
The 40|44 GR wheels are only offered in one build with a Centerlock DT Swiss 350 EXP hub set with a 36t ratchet. At the time of launch, they are offered with HG or XDR freehub options. That means if you’re running the new Shimano GRX 12 speed 1x group, you’ll have to purchase a Microspline freehub separately. Note that the new Shimano GRX 12 speed group is split on its freehub use – 2x groups still use HG freehubs, while 1x use the Microspline.
Reserve 40|44 GR Actual Weight
With claimed weights of 425g and 445g for the rims, the complete wheels check in at 684g for the front and 791g for the rear. Those weights are with tape and the included Fillmore valves installed, so it seems the wheels are well within the claimed weight of 1444g for the set.
Reserve 40|44 GR Initial Review
Reserve sent over a set of the new wheels, and I was excited to check them out – mainly because I wanted to see what riding a rim this wide would feel like on a gravel bike. Out of the box, the rim tape on both wheels needed some attention. One wheel had the valve hole punched in the tape so it was an oval that the Fillmore valves wouldn’t seal. The other had the end of the tape lifting up, so both rims required some extra tape to be added to offer an air-tight seal. We’ve seen similar issues on other brand wheels from time to time, so it’s not a Reserve specific issue. Just be sure to inspect your tape before installing the tires and valves, and if there’s an issue Reserve will help you out.
I was also planning to run these wheels on a bike with a GRX 12-speed 1x drivetrain which required a Microspline freehub. As mentioned above, Reserve isn’t offering a Microspline option yet, so I sourced my own. It was an easy swap, and the hubs were ready to go.
It’s still pretty wet outside, so I opted to install some WTB Raddler 700c x 44mm tires I had on hand. While the first tire bead was a little tight to install, the second bead went on easier without tools. With some sealant in the tire, the beads seated very easily, immediately sealing without any additional effort.
When I’ve used the Raddlers previously, they’ve never quite measured a true 44mm. But on the 40|44 GR wheels, they measured 44mm almost immediately. One thing is for sure, rims this wide will impact the shape of narrower tires. On the Raddlers, the tread ends up fairly flat, with the widest point of the tire being the sidewall by a large margin.
On my first few rides, the 40|44 GR wheels are easy to love. In my opinion, the Raddlers aren’t a particularly fast tire, especially on pavement. Yet when mounted to the Reserve wheels, they feel faster than I remember. Coupled with the carbon rims, the ride quality is fantastic – which is only accentuated by the quiet freehub of the DT Swiss hubs. I don’t mind loud freehubs on the mountain bike, but on the road or gravel, I find the louder hubs more intrusive.
I can’t say that the wheels felt particularly aero, but the sense of speed and stability seems to reinforce Reserve’s claims. Considering that these wheels are guaranteed for life with free replacements, I would not hesitate to buy these for daily use even though they’re the perfect option for your next gravel race.
