Argon 18 Dark Matter GRX Review

Argon 18 makes race-bred bikes, full stop. So, when it came time to launch a gravel bike, the crew from Montréal didn’t shy away from the fact that the Dark Matter maintains Argon 18’s race DNA. I first saw “Goldie” (what I call the gold-colored Dark Matter) at the 2018 Sea Otter Classic and it has been on my shortlist since then. Two years later, it’s here and after a few hundred miles, the Argon 18 Dark Matter has won me over with its fast and efficient take on gravel riding.

2020 Argon 18 Dark Matter GRX Features:

• Monocoque T700 mid-modulus carbon fiber
• Removable front derailleur mount
• Simple, clean internal cable routing
• 3D+ head tube for responsive steering and personalized fit
• Shimano GRX RX810 groupset
• GRX 1x 40t crankset with 11-42t M7000 cassette
• HED Ardennes GP Plus tubeless wheelset
• Challenge Gravel Grinder 700x42c tires
• FSA stem and NS Adventure flared bars
• Argon 18 TDS-C carbon 27.2 seatpost
• Up to 45mm tire clearance
• Weight: 19.6 lbs complete (medium, actual)
• MSRP: $4199

It all started in Monterrey

On a beautiful spring day at 2018 Sea Otter Classic, the Argon 18 crew were showing off their golden-clad gravel bike — the Dark Matter.  I got a detailed overview of the new bike, its features and Argon 18’s take on the segment. While the Dark Matter is built to be on the racy side of the spectrum, it’s plenty versatile for all-day gravel adventures. While some gravel bikes are built for either 700c or 650b wheels, Argon 18 states that the Dark Matter is built for and recommended with 700c wheels in mind. With up to 45mm tire clearance, you can fit some wide rubber on there to add capability and comfort.

For 2020, the Dark Matter is available with Shimano’s full GRX RX810 1x mechanical groupset. I waited specifically to test this build and it was worth the wait. It doesn’t take long to remember just how dialed Shimano’s mechanical groupsets are.

The Dark Matter isn’t a lightweight frame by any stretch of the imagination (~1300 grams), but it’s built with rugged features that you’ll appreciate for years to come. There’s a rubber downtube/bottom bracket protector as well as rubber chainstay protectors. As rocks are flying around on the road, the added protection adds peace of mind. I much prefer the dead thud of a rock hitting rubber versus the telltale “ting!” it makes when hitting bare carbon.

Rounding out the frame features, it also has a drain port at the low point of the dropped chainstay (just in case stream crossings are a part of your regular rides). And, it features Argon’s 3D+ head tube that gives riders the sleek look of a slammed stem at 0, 15 or 30mm stack height. Not only does it look good, but the system maintains proper steering stiffness regardless of your stack height. If you need extra tall stack, you can go up to 60mm, which is something that you would never want to do with any other frame. It’s a cool feature that’s found throughout the Argon 18 lineup.

And, it continued to Utah

On my home turf, the Argon 18 Dark Matter was subjected to the typical test loops that I use for all gravel bike tests. These loops consist of between 20-40% gravel, some singletrack and a good portion of tarmac. The reality is, unless you live in the Midwest United States, you’re still going to want your gravel bike to be at home on paved roads, group rides and local gran fondos. That’s one of the best characteristics of the Dark Matter — it’s a proper road bike at heart, so rolling on the road is delightful. Road climbs are excellent and it’s easy to throw power down, when necessary. Plus, it descends capably and is super-stable.

Stepping on the Dark Matter, you’ll immediately notice how cohesive it feels. The combination of the 3D+ cockpit and stable, but responsive geometry really makes for a lively ride. I find myself hopping over obstacles and generally playing around on this bike in a way that’s not always common. It just feels immediately comfortable and solid. For my fit, I opted for the 15mm top cap with 10mm of spacers under the stem and I swapped the saddle for the stubby PRO Stealth Offroad. Again, dialing in the fit on this bike is a breeze.

Cockpit duty is an FSA affair with 44cm NS Adventure Compact flared bars providing the handling. The overall shape and width are great and the flare is nice to have when things get dicey, but there’s no getting around how stiff these bars are. On my list of upgrades would be a better alloy or carbon bar to smooth things out (or installing a Redshift ShocksStop Stem). It was most noticeable at first, when jumping from other bikes, but became less jarring with time. In a recent compliance test, the Dark Matter’s curved fork actually tested quite well, so I blame it on the stiff bars.

The rear end of the bike is very compliant — thanks to ample seatpost and frame deflection. Off the bike, you can depress the saddle and the whole seatpost and dropped-stay frame visibly flexes under load. In the saddle, the comfort is palpable and well-received on the roughest terrain. On any bike, the best way to add comfort is to let air out of your tires. With that, the Challenge Gravel Grinder 42c tires weren’t my favorites overall. Initially, the bike arrived with tubes installed (kind of a head-scratcher), so I was riding just over 40 psi to avoid pinch flats. On the 21mm internal width HED Ardennes Plus GP wheelset, these measure out to 43.3mm, which is about as large as I’d go on this frame for proper mud clearance.

After a couple of rides, I decided to convert to tubeless. HED makes great tubeless wheels and the Challenge Gravel Grinder’s are tubeless-ready, so it should be a breeze. Install and seating was a snap (with the help of the Blackburn Chamber floor pump). A quick tubeless change allowed me to reduce pressure for more comfort. However, while the Gravel Grinder tires did seat up quickly, their sidewalls are porous and they let air escape in a jiffy. A 2-hour ride could easily result in a 4-5 lb. pressure reduction due to seepage (see the porous sidewalls). And, setting the bike on the wall for a couple of days always resulted in completely flat tires, which was annoying. To fix this, I had to double the amount of sealant that I usually add to tires of this size and, after copious amounts of seepage, things finally improved. 

On the proper terrain, the tires are a great choice. The tire/wheel combo actually rolls extremely well on the road and performed among the best combos in my standard roll-to-stop tests. For hard packed trails and gravel, these tires are great, but on steep or loose terrain, the rear tire does lose traction pretty quickly. I’d get something a little more aggressive and with reliable tubeless performance (something like the Specialized Pathfinder Pro or WTB Venture).

The ideal Dark Matter rider

When considering a gravel bike, you need to ask yourself if you want something more on the adventure/bikepacking side or something on the racy side. If you’re going for the latter, the Dark Matter is an easy choice. Aside from a bento box mount on the top tube, you’d be hard-pressed to get the Dark Matter decked out for a long weekend. But, if you’re a hard-charging roadie, looking to crush all the gravel in sight, the Dark Matter is simply awesome. And, it’s a capable/comfortable bike as well that handles predictably and doesn’t feel sluggish when pushed hard on the road.

One of the best things to do on the Dark Matter is to stitch together a bit of road, singletrack and gravel. And, in this process, I think I may have found my new favorite 25 mile loop with a bit of everything.

I’ve appreciated the Shimano GRX RX810 mechanical groupset and found the shifting to be smooth and chainring gaps to be good overall. Yes, 1x drivetrains do tend to have wide gaps, but I love the reliability and simplicity they provide. It did take me a little time to eliminate random ghost shifts from the 21 to 19t cogs, but I did it. Honestly, it’s refreshing to reach back and twist a knob to make adjustments instead of going through a series of beeps and boops on electronic drivetrains. Braking is excellent, but I’d like to see a 160mm rear rotor to add a little more power. The all-new GRX hoods are outstanding on rough terrain and add a dose of confidence.

The Good

• Balanced, cohesive feel
• Rear end compliance is excellent
• Tackles gravel with speed
• Loves to dabble in singletrack
• Very nimble and fun
• Tons of value in the GRX build
• HED wheelset rolls fast and are great for tubeless
• 3D+ head tube maintains steering precision
• Shimano GRX 1x groupset shifts well and brakes with precision

The Bad

• Stock tires have porous sidewalls
• FSA bars are stiff (but they are 44cm wide, which is nice)
• 160mm rear rotor would give added braking power
• Full build is a little heavy

The Bottom Line: Argon 18 Dark Matter GRX

I really have had a blast on the Dark Matter. It’s everything I imagined it would be — fast, fun, capable, comfortable and smooth. For me, a racier gravel bike is preferred and this one ticks off all the boxes. And, if you add in the sleek 3D+ head tube and 45mm tire clearance, Argon 18 has delivered a quality, fast-riding gravel bike that will put a smile on your face on mixed terrain.

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