Ridley Astr: 52 mm with a 1x drivetrain, 47 mm with 2x. Stock builds ship with a 47 mm Vittoria Terreno T50.

Ridley Kanzo Fast: 42 mm officially, with 38 mm Vittoria Terreno Dry tires stock on most builds.

That 10 mm gap is the headline difference between these two bikes. On chunky Midwest gravel or wet Belgian forest tracks, it's the difference between rolling through and walking.

The Astr, by a clear margin. The Astr RS frame comes in under 900 g and a complete top-spec build with SRAM Red AXS XPLR and DT Swiss carbon wheels weighs around 7.6 kg — light enough to embarrass plenty of road bikes.

The Kanzo Fast's complete builds typically land between 8.2 kg and 8.8 kg in size M, depending on wheels and groupset. Tire inserts on race builds add a touch more. Equivalent trim, the Astr is roughly 0.5–1.0 kg lighter.

Yes — both use deep, NACA-profiled tube shapes, dropped seatstays, integrated cable routing, and a one-piece carbon cockpit. Ridley publishes a 17 W savings claim for the Kanzo Fast over an 'ordinary' gravel bike at speed, and the Astr inherits the lessons of the Falcon RS road race frame.

The catch: aero gains scale with speed. Below 25 km/h on a winding farm road, you'll never feel them. They start to matter on long, flat, paced efforts — gravel races, fast group rides, and tarmac links between trail sections.

Not really. The Astr has only top-tube and down-tube bottle cage mounts — no fork mounts, no fender mounts, no third bottle, no rear rack provisions. Reviewer David Arthur called the lack of mounts a 'missed trick' for buyers who don't actually race.

The Kanzo Fast is slightly more versatile — it adds dedicated mudguard mounts front and rear, which makes it a viable winter trainer or commuter, but it's still short of true bikepacking duty.

If you want a Ridley with real bag and rack capacity, the Kanzo Adventure is the bike to look at.

Both are firm. Reviewers describe the Astr as 'a firm, firm ride' even on 47 mm tires at 20 PSI — Ridley uses tire volume, not frame compliance, to take the edge off. On 'exposed rocks at high speeds' the ride was called 'quite jarring.'

The Kanzo Fast uses lowered seatstays and a D-shaped carbon seatpost to soak up high-frequency buzz, and reviewers consistently note the seatpost-and-saddle combo as a genuine compliance feature. But moderate to large hits still come through; the comfort 'reaches its limit' on rough or rooty terrain.

Neither is a Giant Revolt or Enve Mog. Both are race tools first.

The Kanzo Fast's frame was designed without a front derailleur mount on purpose — Ridley deleted it to save weight and clean up airflow. Riders who want 2x range have to use the Classified Powershift hub, which adds a two-speed gear to the rear hub (and adds cost).

The Astr keeps the option open: order the 2x setup with a Shimano GRX 800 front derailleur, accept that tire clearance drops from 52 mm to 47 mm, and you're set. It's a more flexible platform — Classified is still available, but no longer mandatory.

Either works. With a wheel and tire swap (slim 28–32 mm road tires on a road wheelset), both transform into credible aero road bikes — Ridley calls this out explicitly for the Kanzo Fast, and the Astr's even closer road-bike weight makes it just as plausible.

The Kanzo Fast has a slight edge for this duty because the mudguard mounts also make it usable in the rain. The Astr is lighter and arguably faster, but if you're buying it specifically for road rides, you're probably looking at the wrong bike — get a Falcon RS or Noah Fast instead.

It depends on your terrain. If your gravel is mostly compact and dry and 38–40 mm tires cover your needs, the Astr's gains are real but marginal — lighter, sharper aero, modern cockpit. It's not a transformation.

If you've found yourself wishing for a 45 mm or 50 mm tire on rougher courses, or you're racing events with mixed surfaces where the Kanzo Fast feels overmatched, the Astr is a clear step forward. The 52 mm clearance changes which races you can sensibly enter on a single bike.