The Obsidian colourway is darker, more understated, and for a lot of riders that's the one they come back to once they've seen both in person.
Underneath the finish, the Specialized Diverge 4 Sport Carbon Obsidian is the same build: FACT 9r Carbon frame, Future Shock 3.1, Shimano GRX 600 1x12, DT Swiss G540 wheels, and SWAT 4.0 internal storage.
At 9.79 kg, it's a lightweight gravel bike that's competitive with anything else at this price point, carbon or otherwise.
The frame
FACT 9r Carbon gives the Diverge 4 Sport a noticeably different character to the alloy versions in the range. The ride is smoother under rough conditions, more composed on fast descents, and more efficient on longer climbs where a stiffer frame pays back the effort you're putting in.
Future Shock 3.1 handles the front-end compliance, a 20mm travel unit in the headtube that takes the repetitive vibration out of long gravel days without softening the handling. On the kinds of tracks and bridleways you find across the UK, it earns its place quickly.
Shimano GRX 600 1x12
GRX is purpose-built for gravel and mixed-terrain use. The clutch derailleur keeps the chain where it should be over rough ground, the gear range is wide enough for loaded or technical riding, and the 12-speed steps are fine enough to hold a proper rhythm on long climbs.
For a carbon fiber gravel racing bike at this price, having GRX 600 rather than a road-derived groupset matters. It's designed around the conditions you'll actually ride in: mud, loose gravel, wet descents, and long days where mechanical reliability matters as much as performance.
DT Swiss G540 wheels are tubeless-ready and built to take repeated rough-road use without constant fettling.
SWAT 4.0 storage
The internal downtube storage on the carbon Diverge 4 Sport is SWAT 4.0, a step up from the 3.0 system on the alloy models. Enough room for a tube, levers, and a multi-tool, all inside the frame and out of the way. Useful on a gravel off-road bike where a saddlebag can interfere with certain frame shapes or bikepacking setups.
Specs at a glance
- Frame: FACT 9r Carbon
- Suspension: Future Shock 3.1 (20mm travel)
- Drivetrain: Shimano GRX 600 1x12
- Wheels: DT Swiss G540
- Storage: SWAT 4.0 internal frame storage
- Weight: 9.79 kg
Who this suits
Anyone who wants to buy a Specialized Diverge 4 Sport in a colourway that doesn't announce itself is the obvious answer. But beyond the aesthetics, this is the same strong case as the Emerald: a legitimate carbon gravel bike with a gravel-specific drivetrain, proper internal storage, and a weight that sits comfortably among the best carbon gravel bikes in 2025 and 2026 at this price.
Works for gravel sportives and racing, longer bikepacking routes, and the kind of UK riding that involves a bit of everything over the course of a year.