Review: Viathon G.1 Carbon Gravel Bike – Cyclocross Magazine

Earlier this year, Viathon Bicycles launched with a direct-to-consumer business model and a catalog of high-end carbon bicycles, taking an approach similar to the one Canyon has used.

Viathon’s G.1 carbon gravel bike is Walmart’s attempt to capture some of the high-end, direct-to-consumer bicycle market. © A. Yee / Cyclocross Magazine

The brand, which is a property of Wal-Mart, is helmed by industry veterans with design and engineering provided by Kevin Quan Studios, one of the bright minds behind Knight Composites.

We welcomed a demo G.1 gravel bike for a review. Did Wal-Mart do its homework before its first foray into high-end bikes and gravel? We were anxious to find out.

The Frame

Some cyclists couldn’t care less about the owner of their bike’s brand, while others may steer clear of a bike from the famous big-box retailer without local bike shop service. The rest might be skeptical of such a venture. Perhaps the G.1’s stats could reassure wary consumers?

The G.1, one of 3 models launched by Viathon, is a modern gravel bike with a 1,010g claimed 54cm frame weight with hardware. Thanks to a dropped chainstay design, the G1 clearance for 700c x 40mm or 650b x 2.1” tires and a maximum chainring size of 50t, according to the website, while boasts 700c clearance up to 51mm tires. Take your pick, there’s a lot of room.

The Viathon G.1 has plenty of clearance for wide tires. © A. Yee / Cyclocross Magazine

The Viathon G.1, like all Viathon offerings, is a full carbon frame and fork. As expected, the frame features 12mm thru-axles front and rear with flat mount brakes and internal cable routing by way of removable cable stops.

Viathon’s G.1 carbon gravel bike routes everything internally. (Our tough testing left a battle scar.) © A. Yee / Cyclocross Magazine

Home mechanics will rejoice at the inclusion of an English threaded bottom bracket. For further utility, the frame is equipped with fender mounts and threaded bosses for both front and rear racks as well as an adventure-ready three bottle cages.

Viathon’s G.1 carbon gravel bike review has you ready for wet riding or hauling gear with fender and rack mounts. © A. Yee / Cyclocross Magazine

Geometry is versatile with 582mm of stack and 387.6mm of reach for a size 56. The frame boasts a moderate 72-degree head tube and 48mm fork rake, yielding 61.9mm of trail, coupled with 42.5cm chainstays and 6.9 cm of bottom bracket drop. Sizes 56 and smaller have slightly steeper-than-average seat tube angles, with the 56cm featuring a seat tube angle of 73.5 degrees. Racers with a more setback position will want a setback post, and consumers trying to decide on an appropriate size should value the reach numbers over top tube lengths.

Despite the gravel-oriented name, the G.1 could easily pass for a cyclocross bike with its geometry. While we try to avoid putting much weight on labels and categories used in marketing, could the G.1’s build justify the gravel label?

The Build

With a price tag of $2,999, the G.1 Ultegra boasts an impressive spec list, but one that skews a bit more cyclocross than gravel. It includes a full Shimano Ultegra R8000 hydraulic disc groupset with the cyclocrosser’s standard of 46/36t chainrings.

Out back, there’s an 11-32t cassette, not the 11-34t made popular by the RX and GRX drivetrains. Although the G.1 is built with a 2x drivetrain, we’re surprised to see a non-clutch R8000-GS rear derailleur rather than an RX800 or GRX clutch derailleur. (Update: new production models are shipping with the RX800 rear derailleur, as shown on but not Viathon’s website.)

We’d replace the Ultegra Shadow rear derailleur for a clutch-based RX800 or GRX rear derailleur, but we only dropped our chain once. New production models now ship with the RX800, thankfully. Viathon’s G.1 carbon gravel bike review. © A. Yee / Cyclocross Magazine

A common way to save money on a build is by using a cheaper third party option where it’s harder to spot like the bottom bracket, but the G.1 features an Ultegra level BBR60 bearing set. Similarly, the bike ships with a Shimano HG701 chain.

The G.1 Ultegra comes out of the box with HED Ardennes LT wheels, which feature a tubeless-ready 21mm internal width rim and straight steel spokes for a 1549g claimed weight. Braking is handled by 160mm RT800 Centerlock rotors front and rear.

The G.1 also skews more cyclocross than gravel with its narrow-for-gravel 35mm Continential CycloX King tires. Maybe the width is moot, as the CycloX King is a tube-only tire, which many gravel or cyclocrosser racers will end up replacing. It’s a shame, because it’s a grippy tread and has decent volume for cyclocross. Continental finally offers tubeless tires, and they’d be an appropriate spec on this bike.

HED Ardennes tubeless wheels unfortunately come with non-tubeless 35mm Continental CycloXKing tires. Viathon’s G.1 carbon gravel bike review. © A. Yee / Cyclocross Magazine

Viathon didn’t skimp in the area of cockpit components—no generics or house brand components here. The G.1 comes with alloy Zipp Service Course SL bits for the handlebar, stem and seatpost.

Viathon’s G.1 carbon gravel bike doesn’t penny pinch with house brand components and features a Zipp Service Course SL cockpit. © A. Yee / Cyclocross Magazine

Interestingly, the G.1 ships specs list a zero-offset post, which in conjunction with a steeper seat angle, pushes the rider further forward than is typical of road or cyclocross fits. Thankfully, our test bike had some setback with a Service Course setback post for a familiar position, but Viathon made a running change and current models ship with the zero-offset but lighter SL version.

Viathon, just as with its cockpit, doesn’t cut corners in saddle choice. The post is topped with a name brand pick, a 138mm Fizik Aliante R3 saddle.

A two-bolt Zipp Service Course seat post offers a secure, name brand perch but production models ship with a zero-offset SL model. Viathon’s G.1 carbon gravel bike review. © A. Yee / Cyclocross Magazine

Notably, especially for a gravel oriented build, the bar is wrapped in white Fizik tape. Wash up after you make a mess, okay?

The entire package is reasonably light. Our 56cm test bike tipped the scales at 18.8 pounds, without pedals. If you’ve got your own race wheels, you’ll be putting them on a build that weighs a respectable 11.4 pounds without wheels. Of course, if you swapped out the heavy inner tubes for a splash of sealant and a lightweight tubeless tire, you could save more weight.

The Ride

Out of the box, the Viathon G.1 is capable but may send you riding to your local shop for some immediate upgrades. The Continental cyclocross tires are grippy and thankfully, at 35mm, don’t mistakenly adhere to UCI tire width rules. Still, they’re quite narrow and aggressive by current day standards for gravel.

Even worse, they’re not tubeless-ready, even though Continental has finally embraced tubeless and other brands have plenty of other capable gravel options. Spending $100 or more on new tires and valves to take advantage of the HED Ardennes tubeless wheels should be factored into any purchase decision. To avoid pinch flats and goat head flats, we spent much of our test time riding other wheels and tires, and the stock wheels and tires with Tubolito tubes (stay tuned for that review).

There’s plenty of clearance around the 35mm Continental cyclocross tires. We’ve fit 47mm gravel tires, and wish the bike came with something bigger that’s already tubeless-ready. Viathon’s G.1 carbon gravel bike review. © A. Yee / Cyclocross Magazine

Getting past the Viathon’s short-sighted tire choice, the Viathon is one of the more capable carbon frames we’ve tested recently. The G.1 boasts impressive tire and mud clearance for both gravel and cyclocross escapades. The frame’s official clearance is listed at 40mm on 700c wheels (and 51mm on, and it clears Soma Fabrications’ excellent 50mm Cazadero gravel tires (which measured 47mm on Easton EC90 AX test wheels).

That opens up a world of options for both cyclocross and gravel. Race cyclocross in the mud without pitting and ride the roughest gravel or chase mountain bikers with big-volume tires. Gravel tires keep getting bigger, and the Viathon is ready for tires bigger than 40mm. We picked the Viathon G.1, armed with 50mm tires, for a bumpy cyclocross race.

Mud clearance or tire clearance? The Viathon’s G.1 carbon gravel frame and fork have both. A 50mm (47mm measured) Soma Cazadero gravel tire has some room to spare. © A. Yee / Cyclocross Magazine

If you do max out that tire clearance, watch your toes and front derailleur cable. With 40mm or bigger rubber, size 45 shoes had enough toe overlap that we noticed it while real-world riding technical terrain—not just in parking lot tests. By the crankset, the front derailleur cable end contacts big tires like our 47mm-wide Soma Cazadero.

Viathon’s G.1 carbon gravel bike clears 47mm tires, but you’ll have to clip your front derailleur cable to be extra short to avoid generating unwanted buzz on your ride. © A. Yee / Cyclocross Magazine

All that tire clearance should be a godsend to cyclocross racers, as it translates into great mud clearance without as much toe overlap (unless you’ve stuck with the gravel tire in cyclocross philosophy).

Viathon’s G.1 carbon gravel bike review features a seatstay bridge but that didn’t limit our ability to ride 47mm tires. © A. Yee / Cyclocross Magazine

Mother Nature has not yet served NorCal with mud this season—at least at the time of writing—but the G.1 should keep any rider sprinting past the pit, rolling free and unclogged on muddy days. Let the traditionalists laugh at your gravel bike choice while you leave them stuck in the mud.

Viathon’s G.1 carbon gravel bike features a versatile frame. As equipped, the bike is better-suited for cyclocross than gravel. © A. Yee / Cyclocross Magazine

Some might even mistake your ride for a Santa Cruz Stigmata, or you for Tobin Ortenblad. While the G.1 shares sloping top tube and dropped seat stay of the Stigmata, by the numbers, it’s nearly a carbon copy of a Specialized CruX.

You can do the full comparison with a 56cm Crux, but we’ll give you some proof. A 56cm G.1 shares the same stack, head angle, chainstay length and bottom bracket drop, while the trail and reach are within 1mm. The biggest difference? The G.1 has a 5mm longer head tube and 2mm shorter wheelbase and front-center (remember that toe overlap?).

Mud clearance or tire clearance? The Viathon’s G.1 carbon gravel frame and fork have both. This is with a 47mm (measured) Soma Cazadero tire. © A. Yee / Cyclocross Magazine

We gushed over the Specialized Crux frame and nitpicked our S-Works build package. While a bike’s handling is influenced by more than just geometry, it looks like Viathon took a winning cyclocross formula and added even more tire clearance. That’s a safe bet, and one that should serve a cyclist who races both cyclocross and gravel quite well.

Those with pro-level watts should be pleased as the frame is quite stiff. You’ll need to lean on tire volume and pressure for a compliant ride. The boxy tube shapes and compact rear triangle help translate your effort into forward momentum and tire flex. Sprinting out of corners, up steep hills and navigating taped hairpins, it feels and handles like a race bike, not like a bike aimed at gravel and bikepacking designed to go straight for hours at a time.

On the run-up, the big, boxy tubes are a plus when the G.1 is resting on your shoulder. Its light weight and big tubes don’t leave a dent thanks to its boxy, flattened top tube shape.

The Verdict

If you can ignore the big G in the model name, and don’t value local bike shop service, the G.1 makes a strong case for a one-bike candidate. It’s got fender and rack mounts for commuting, versatile and moderate geometry that doesn’t steer towards slow tours or grass crits. And it’s more-than-ready to tackle your local cyclocross race.

As a gravel bike, our Ultegra-equipped G.1 test bike misses the mark with its rear derailleur, cassette, chain rings and tire selection. It’s a build we might have applauded five years ago but feel it’s lacking many of the features we’ve grown to appreciate in modern gravel bikes: high-volume tubeless tires, low gearing and chain security. Thankfully production models are now shipping with the RX800 clutch-based rear deraileur, but we’re still longing for lower gears and bigger tubeless tires.

Yay or boo? Viathon’s G.1 carbon gravel bike came with 36/46 chainrings, perfect for cyclocross duty, but perhaps not quite as low or wide as we’d want for long gravel days. © A. Yee / Cyclocross Magazine

However, as a 2x cyclocross bike, the G.1 has so much potential. The build is appropriate, the geometry is spot-on and the mud clearance is supreme. With geometry that nearly mirrors a Specialized CruX, you can even argue the Viathon G.1 is more of a cyclocross bike in gravel clothing, if labels are your thing.

Many of us race cyclocross, ride gravel and hit the trails, all on the same bike. If racing cyclocross is what gets your heart racing the most, you’re in luck with the G.1.

Although the Ultegra build has a few flaws as a gravel build, Viathon offers other build kit options including SRAM Force AXS eTap and Shimano 105.

Want to build your own Wal-Mart dream bike? Viathon didn’t originally offer the frameset by itself through its direct-to-consumer model, but now it does. Rejoice, because the G.1 frameset is a winner.

Andrew Yee and Brandon Grant contributed to this review.

Viathon G.1 Ultegra Gravel Bike Specs:

Frame: Viathon G.1 Carbon frame, 1010g claimed weight (54), internal cable routing, 12x142mm thru-axle, flat mount disc brakes, threaded bottom bracket, rack and fender mounts
Fork: Viathon G.1, full carbon, rack and fender mounts, internal brake routing, flat-mount brakes, 12mm thru-axle
Shifter: Shimano Ultegra R8020 integrated shift-brake levers, 11-speed mechanical shifting, hydraulic disc brake
Brake Calipers: Shimano Ultegra R8070 flat mount
Rotors: Shimano RT800, Centerlock, 160mm front and rear
Bottom Bracket: Shimano Ultegra BBR60, 68mm BSA
Crankset: Shimano Ultegra R8000, 46/36t chainrings
Cassette: Shimano Ultegra CS-R8000, 11-speed, 11-32t
Front derailleur: Shimano Ultegra R8000
Rear derailleur: Shimano Ultegra R8000-GS (on test bike), RX800 (on current production models)
Chain: Shimano Ultegra HG701
Wheels: HED Ardennes LT Disc, tubeless-ready, 21mm internal width, Centerlock disc mounts, 12mm thru-axle, 11-speed Hyperglide freehub, 1,549g claimed weight.
Tires: Continential CycloX King 700c x 35mm, non-tubeless
Handlebar: Zipp Service Course SL 70, alloy
Stem: Zipp Service Course SL, 110mm alloy
Seatpost: Zipp Service Course SL, zero setback, alloy (official spec, non-SL with setback on our test bike)
Saddle: Fizik Aliante R3, K:ium rails, 138mm width
Weight: 18.8 pounds without pedals, 11.4 pounds without wheels
More Info:

Viathon G.1 Gravel Bike Photo Gallery: