Gravel vs. XC MTB: 100 Miles Off-Road: Which Is Faster?

GMBN took the “gravel vs cross-country MTB” debate out of the comments section and onto a brutally honest test: the Cotswolds 100, a 168 km loop starting and finishing in Bath with 3,000 m of climbing, ridden at FKT pace. The route was the perfect mixed-terrain reality check: roughly 100 km paved, 30 km fast gravel, and around 40 km of genuinely rough off-road where line choice and control mattered as much as speed. Both bikes rolled on Reynolds Blacklabel wheels making this not just a bike comparison, but a clear showcase of how the right wheelset shapes performance on either side of the “drop bar vs flat bar” divide.

The Setups XC Bike: Reynolds Blacklabel XC 309 The mountain bike build featured Reynolds’ new Blacklabel XC 309 wheelset, with a 30mm internal width, a new asymmetric rim profile, and Reynolds’ MR5 carbon layup. Paired with a 2.4” tire, the wide internal supports modern XC rubber for stability, traction, and confidence, especially when fatigue sets in and the terrain gets unpredictable. Gravel Bike: Reynolds Blacklabel ATR On the gravel side, the bike ran the Blacklabel ATR (All-Terrain Road) wheelset: a 42mm-deep rim with 25mm internal width, aero-optimized for 35–45mm tires, exactly the range they used (45mm front and rear). With tire inserts added for peace of mind on rough descents, the gravel setup was built to stay efficient on long paved stretches while still handling real off-road conditions.

What the Ride Revealed On the road-heavy sections, the gravel bike’s efficiency showed immediately: more aerodynamic position, multiple hand positions, and sustained speed that’s hard to match on an XC bike over long pavement. When most of your day is fast rolling and paved connectors, that advantage adds up. But the minute the route turned chunky and technical, the XC bike clawed time back. Suspension, tire volume, traction, and control all mattered, not just comfort, but the ability to carry speed safely and consistently through rough descents and steep, loose climbs. The key takeaway from the presenters was simple: the route didn’t reward one category universally. It rewarded the right tool for each section, and they even concluded that a “middle ground” setup (think XC speed with drop-bar efficiency) could be the ultimate solution.

The Reynolds Thread Through Both Bikes That’s exactly why Reynolds matters in this discussion. Whether you’re chasing speed on mixed-surface roads or pushing hard through technical XC terrain, Reynolds builds wheelsets designed for the demands of modern riding:

MR5 carbon layup tuned for the balance of speed and real-world resistance
Asymmetric rim design to help balance spoke tension and durability
Purpose-built internal widths to properly support today’s wider tires
Blacklabel-level performance across both gravel and MTB categories

Two very different bikes. One consistent theme: wheels that keep speed high when the route refuses to be predictable.

Gravel vs XC? Depends on the Route. If this video proved anything, it’s that “gravel vs XC” isn’t a clean binary, especially in places where riding flips quickly from pavement to rough trail. Sometimes aero efficiency wins. Sometimes traction and control win. Most of the time, it’s a mix, and the right wheels help you stay fast through all of it.