FAST GRAVEL BIKES

Argon 18 Dark Matter Force AXS XPLR

£5,500 | Rugged racer from Canada

Weight 8.54kg (L) Frame Carbon Fork Carbon Gears SRAM Force AXS XPLR (10-44, 42) Brakes SRAM Force Hydraulic Wheels Hunt 42 Limitless Gravel Disc XDR Finishing kit Argon 18 TDS seatpost, Prologo Scratch-M5 AGX saddle, FSA OS-99 stem, FSA A-Wing Pro AGX handlebar, Vittoria Terreno Mix TLR G2.0 40c tyres

Argon 18 describes the Dark Matter as a performance gravel bike that’s as at home racing as it is being a rough, rugged adventurer. That’s quite a bold claim, though the frame and fork do combine elements of both sub-disciplines of gravel riding. For the racer, the steep seat angle and race-adept head angle will be welcome. For the bikepacking adventurer, the myriad of mounts and taller stack will appeal.

The chassis uses Argon’s TCS design method, which combines frame design and tube shaping with the physical properties of the carbon fibre to maximise stiffness where needed and introduce more compliance where vibration damping is a must. If you draw a line from the top of the head-tube to the rear axle, everything below is maximised for stiffness, and for accurate steering and optimal power transfer. Above that line, the top-tube, seat-tube and seatstays are all designed for compliance to absorb vibrations. The tapering fork with its forward sweep is also designed to absorb chatter while maintaining steering accuracy.

There are lots of fittings: front and rear mudguard mounts, top-tube mounts, twin bottle mounts on the seat-tube and six bottle bosses on the down-tube, plus triple anything mounts on the forks. And the down-tube has armour to protect it from rock strikes. The bike still weighs within a few grams of the other test bikes though.

Dropped chainstays and a broad fork bring a generous 45mm tyre clearance, while Argon’s 3D head-tube system integrates the headset top into the frame and allows internal brake hose routing. I chose the 0mm 3D top piece, but the 25mm option heightens the stack without compromising stiffness with spacers.

The steep seat and head angles are similar to road endurance geometry, and the stack is the tallest here, but the bike also has a generous reach (the reach shortens with the 25mm 3D headset topper). The long chainstays and wheelbase help with stability in the rough.

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Built to last

This is the range-topping model, and the build reflects that. At its heart is SRAM’s latest Force AXS XPLR groupset, a step up from the Cervélo’s Rival AXS and an update over the Riverside. The gearing is the most performance orientated of our trio, mixing a 42t chainring and 10-44t XPLR cassette, for speed on and off-road.

The bike rolls on Hunt’s hugely broad 42 Limitless gravel wheels, with rims 42mm deep and 25mm internally. Hunt says these give aero advantages optimised for 38-40mm gravel tyres. Vittoria’s Terreno Mix 40c tyre are good all-rounders and they come set-up tubeless here.

“Its comfort and practicality make the Dark Matter a star performer for long, multi-day events”

FSA’s cleverly shaped A-Wing Pro AGX alloy bar combines a flattened, ovalised top section with a subtly flared compact drop and is wrapped in excellent cushioning bar tape. At the back, Argon 18’s compliant carbon seatpost is topped with ProLogo’s brilliant gravel-specific Scratch-M5 AGX saddle with slightly beefed-up padding.

A solid partner

The Dark Matter is fast and smooth on mixed surfaces; it feels like a great endurance bike but its tall gearing helps it maintain road-bike pace on tarmac.

In its natural habitat it excels too, with a subtly compliant feel that’s superior to the Riverside GCR, especially when things get rough. But the Áspero beats it in that regard: rear comfort is a match, but the front feels a little harder, so it would be worth upgrading to a high-quality carbon bar like the Cervélo has, at some point.

Similarly, while the Dark Matter handles technical terrain and chunky gravel very well and it takes a lot to unsettle the bike, it’s not quite the flickable funster that the Áspero is. The Hunt wheels are fast yet forgiving with a quick freehub pick-up, and the Terreno Mix tyres are brilliant in damp conditions but don’t feel compromised in the dry or on tarmac.

With its slightly relaxed ride position and impressive contact points, the Dark Matter is more endurance bike than racer, its comfort and practicality making it a star performer for long, multi-day events. Its geometry and stable handling wouldn’t disadvantage anyone but the fastest riders in the heat of competition, though.

The Good

Great all-round handling; endurance-biased ride position

The Bad

May not be racy enough for some

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Photography Russell Burton