Gravel Riding is Changing Rapidly: Why Wider Tyres Demand Better Safety Standards
Gravel riding is on the verge of a massive transformation. Behind the scenes, almost every major cycling brand is actively developing products around the 32-inch wheel platform—from custom frames and wide rims to specialized forks and ultra-wide rubber.
However, before the industry forces another standard on riders, we need an honest conversation about how gravel bikes are actually being used—and whether the frame engineering is keeping up with how hard we are pushing them.
Over the summer, Paul at Mapdec Cycle Works put three distinct gravel bikes through their paces across local Lake District routes, tarmac links, and rugged singletrack. Here is what testing these three setups revealed about the real state of gravel biking today.
1. The Accelerated Road Bike: TIME ADHX 45
The TIME ADHX 45 features exceptionally stiff carbon layup and precise handling. When taking it down technical Lake District descents, its rigid construction allows skilled line-picking through rocky terrain.
However, with 45 mm of maximum tyre clearance, its geometry and clearance profile function far more like an extended road or endurance bike. Running slick or semi-slick tires makes it brilliant for fast tarmac transitions, light gravel, and back-road touring.
The ASTM Rating Gap
Modern "all-road" bikes designed around 40 mm–45 mm clearance often carry an ASTM 1 rating:
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ASTM Category 1: strictly designed for smooth road surfaces with continuous tire contact (zero drop rating).
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ASTM Category 2: designed for cyclocross/paved surfaces with smooth drops under 15 cm (6 inches)—essentially the height of a standard street curb.
If you hop off a curb or pick through a modest drop on a trail, you are already pushing an ASTM 1 or 2 frame into safety-margin territory. While the TIME ADHX 45 remains a fantastic, high-performance option for light multi-surface rides, calling modern 45 mm bikes "true gravel" is becoming a stretch.
2. The Do-It-All Benchmark: Wilier Rave SLR
The Wilier Rave SLR strikes a sweet spot between race-line speed and real-world compliance.
| Feature | Wilier Rave SLR Specs |
| Tyre Clearance | Up to 55 mm |
| Frame Design | Aerodynamic, fully integrated cabling |
| Best Suited For | Group rides, unknown routes, mixed tarmac & trail |
| Handling | Nimble, fast-rolling, high compliance |
3. The Super-Wide Trend: 3T Extrema Italia (57 mm Clearance)
Driven by massive multi-surface races like Unbound Gravel and the Trailfinder series, frame clearances are pushing 57 mm to 60 mm+. To test this ultra-wide trend, we spent significant time on the 3T Extrema Italia.
The High-Volume Dilemma
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Speed on True Gravel: On pristine, unpaved endurance courses, 57 mm tyres carry insane momentum and traction over loose surface layers.
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Drag on Tarmac: On mixed European routes or local road connectors (like the Rebellion Way in Norfolk), 57 mm rubber feels slow, heavy, and draggy.
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The Confidence Trap: Ultra-wide volume provides massive cushioning, encouraging riders to hit rock gardens and singletrack at mountain-bike speeds.
Hitting mountain bike features at high speed on a drop-bar bike built around cyclocross frame tolerances creates a major structural mismatch.
The Case for New Safety Standards: ASTM 2.5 and MTB Axle Dimensions
If the cycling industry continues to push 60 mm tyre clearances and 32-inch wheel platforms, frame engineering standards must change alongside tyre width.
1. Introducing an ASTM 2.5 Drop Rating
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ASTM Category 3 covers mountain bikes tested for 61 cm (24 inch) drops.
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Gravel bikes need an intermediate ASTM 2.5 rating to guarantee frame, handlebar, and wheel impact resistance when running wide tires at speed over rough terrain.
2. Transitioning to Mountain Bike Standards
Running 2.25-inch (57 mm+) tires on standard road axle widths (12x142 mm) and narrow road bottom brackets (68 mm) strains frame clearances and bearing durability.
Just as the mountain bike industry shifted from 68 mm to 73 mm/89 mm bottom brackets and 148 mm Boost spacing when tires widened, extreme gravel bikes need to adopt wider stance widths and reinforced axle hubs.
Summary Checklist: What to Look For in Your Next Gravel Bike
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Match Your Local Terrain: If your rides are 60% tarmac and 40% light gravel, look at endurance/all-road setups with 40 mm–45 mm clearance.
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Check the ASTM Rating: Ensure your frame's safety category matches the drops, curbs, and trail obstacles on your regular routes.
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Consider Rolling Resistance: Ultra-wide 57 mm+ tyres excel on continuous loose gravel, but add drag on road connectors.
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Look at Hardware Standards: Pay attention to axle width and bottom bracket design if you plan to run tires over 2.0 inches.
Join the Conversation
Is your current gravel bike handleable like an agile road bike, or are you charging down technical singletrack on 57 mm rubber? Do you think manufacturers should adopt wider MTB axle standards for extreme gravel, or should gravel stay light and simple?
Drop your thoughts in the comments below, or visit the workshop at Mapdec Cycle Works to discuss custom gravel builds, frame fits, and suspension setups.
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