Stan’s NoTubes needs no introduction as one of the industry leaders in tubeless technology. The company’s Valor rims have made their way into the professional cyclocross ranks and the Iron Cross, Valor and Avion wheels are popular with the cyclocross and gravel crowd.
Today, Stan’s NoTubes officially announced the expansion of its gravel and cyclocross wheel line with the new carbon Grail CB7 and alloy Grail MK3 models. Geoff Kabush, Kae Takeshita, Jake Wells and our own Andrew Yee tackled the biggest weekend in gravel on the new Grail CB7 carbon wheels at Dirty Kanza and Lost and Found, and we’re bringing you the details and initial impressions after a few weeks of riding.
Stan’s Grail CB7 Carbon and Grail MK3 Alloy Tubeless Gravel Wheels
With both the Grail CB7 and MK3, Stan’s set out to design a wheel specifically for high-volume, low-pressure tubeless riding.
The lightweight Grail CB7 rim has a head-turning claimed weight of 300g and the MK3 checks in at a respectable 440g. Stan’s designed both wheels for optimal performance with the wider tires run at low pressures that are becoming increasingly popular for gravel riding.
Both the carbon and alloy rims use Stan’s patented BST-R tubeless rim shape for ease of inflation and a more secure fit.
With the carbon CB7, the company built an ultra-lightweight rim that has a claimed weight of 300g. For comparison, other carbon rims we have recently looked at have weights at or above 400g each.
All wheels come with rim tape and valves pre-installed for easier setup.
The company was able to achieve the light weight in part by designing the rims specifically for low pressures. With a claimed maximum tire pressure of 85 psi for 28mm, and 55 psi for 40m tires, the company was able to save grams over tubeless road rims designed for 100+ psi pressures.
Short sidewalls and a shallow 19.6mm depth also help reduce material and save weight. These are not aimed to ace wind tunnel tests.
The rim’s 21.6mm internal width (26.4mm external) provides room for wide tires, and it is designed with what Stan’s calls its RiACT impact-absorbing design. Stan’s optimized the Grail CB7 for use with tires 28-40mm wide, which makes them well-suited for cyclocross racing as well.
Full wheelsets come with Stan’s Neo Ultimate hubs that have six pawls and 5-degree engagement and are laced with Sapim Lazer spokes, 24 front, 28 rear.
The full wheelset is listed at an eye-catching 1,277g. Our test set tipped the scale at just 1,274g including tape and valves. Without tape and valves, we estimate the wheels to tip the scale around 1,250g. That’s lighter than most rim brake carbon tubular wheels.
The Grail MK3 alloy wheels join the Grail CB7 as a low-pressure, disc brake offering. The 6069 series aluminum rims have a claimed weight of 440g, which is similar to the alloy Alto AMX29 we recently reviewed.
The internal profile of the MK3 is 20.3mm (external is 24.0mm), and the rim can withstand pressures up to 110psi. Accordingly, Stan’s designed the rims for optimal performance with 25-40mm tires. The alloy wheels are also a bit deeper than their carbon counterparts at 24.5mm.
Full MK3 wheelsets come with Stan’s Neo hubs with Durasync and Sapim Force spokes, 28 front and rear. The full wheelset weighs 1,675g.
Stan’s Grail CB7 Tire Installation
The NoTubes Grail CB7 carbon rim follows NoTubes’ tradition of a reliable rim/tire interface at low pressure.
The NoTubes’ rims, with the exception of the Alpha series of rims, have historically been some of the best options for burp-proof tubeless setups and great candidates to convert non-tubeless tires for tubeless use. The rims’ internal shape, especially the wide shoulders along the center channel and short sidewalls, help lock a tire bead’s in place and keep the tire from sliding over the center channel and leaking air.
We’ve installed Challenge Gravel Grinder TLR 42mm tires, Kenda Flintridge Pro DCT 40mm tires, and a non-tubeless ultralight ChaoYang Merlin 29×1.9 tire. All three installed with a loud snap after several blasts of a tubeless charging pump, and held air with minimal leakage overnight. Would they hold air on the ride?
A 113mm wide (bead to bead) Challenge Gravel Grinder 42mm tire measured at nearly 45mm on the CB7 rim at psi.
Stan’s Grail CB7 Ride Impressions
We’ve had four mixed terrain rides including five hours of rough dirt roads at the Lost and Found to test the new Grail CB7 wheels, and have come away relatively impressed. First, it’s impossible not to notice the weight savings. We’ve tested plenty of carbon disc wheels that weigh nearly a pound or more, and the Grail CB7 300g rims ensure that much of the weight savings are rotating weight—not just the hubs. Hit the accelerator and the wheels respond willingly. Throw the bike on your shoulder, and you might just start looking for more run-ups. You can be sure we’ll be angling to hold onto these test wheels into cyclocross season. Dressed with tubeless cyclocross tires, we’ll be shedding weight over most carbon tubulars.
The Grail CB7 rim provides impressive airtight bead security. With tires as low as 16psi, we tried to bottom out the rim and see if we could burp the beads in corners. While the tire started to fold in corners, it remained airtight, and the wheel remained true.
Pick up a pair of 1250g disc brake carbon wheels and you probably shouldn’t expect the world’s stiffest wheel, and the Grail CB7 Pro wheelset is no exception. On power climbs and sprints, there’s noticeable flex, even under the middling power of a 160-pound tester. How can we tell? On our test bike, with 2-3mm clearance on each side of a 44mm tire at the chainstays, we were scraping away paint during sprints.
Perhaps sprints are rare in gravel, but power climbs may not be—heavier or more powerful riders, or cyclists with limited tire clearance might want to take note—and perhaps look for stiffer build options than our Pro wheelset build.
It’s also worth noting that the weight savings at the hubs comes at the expense of some robustness. The thru axle caps pop off easily and fit loosely, making swaps between 12mm and 15mm caps up front easy, but offering the elements easy access to bearings.
Out back, the rear hub is similar. After accidentally knocking over a rear wheel that was leaning against the wall, we saw a thru axle end cap go flying and the freehub and cassette fall off the hub. Not all was lost—after brushing off some dirt we put it all back together—but the experience revealed the simple but lightweight hub design, which contrasts to threaded axle designs we’ve seen by Alto Cycling and American Classic.
Even with such quirks, the gram-shedding Grail CB7 Pro wheelset is appealing to anyone looking for a reliable tubeless system or with weight weenie tendencies. At $1635 for the top-end Pro wheelset, the price is right in the middle of the range of carbon offerings we’re seeing nowadays. Are they worth the price? We think the answer depends on how they’ll hold up over time. Stay tuned.
Stan’s Grail CB7 Specs
Price: Pro: $1,635, Team: $1,400, Rim: $600
Weight: Rim: 300g (claimed), Wheelset: 1,274g (actual, valves and tape)
Width: 21.6mm internal, 26.4mm external
Hubs: Stan’s Neo Ultimate with Speedsync, 24-hole front, 28-hole rear
Tire Sizes: 28-40mm recommended
Stan’s Grail MK3 Specs
Price: Wheelset: $700, Rim: $105
Weight: Rim: 440g (claimed), Wheelset: (1,675g claimed, valves and tape)
Width: 20.3 internal, 24.0 external
Hubs: Stan’s Neo with Durasync, 28-hole front, 28-hole rear
Tire Sizes: 25-40mm recommended
More Info: notubes.com