Avona Callis: Aero-gravel on 32-inch wheels

​The Callis from German newcomer Avona is one of the first 32-inch carbon gravel bikes. With a design optimised in the wind tunnel and well-thought-out geometry, the bike is set to make a real impression.

​Conclusion: Focus on speed and driving pleasure

The Avona Callis 32 is not a custom bike with large wheels, but a carbon production racer that has clearly been developed with a great deal of technical expertise. As well as the extensive laboratory and practical tests, the focus on an improved riding experience is also exciting. The aim is to combine greater riding enjoyment and safety on challenging terrain with increased speed when it really counts. We’re keen to see how the bike performs in our test. - Adrian Kaether, Test & Technology Editor.

Avona: A small brand with a wealth of expertise

Behind the Callis 32 is Avona, a young company based in Mogendorf, Rhineland-Palatinate – and therefore no unknown quantity. Co-founder and managing director Jonas Müller has developed products for companies including Arc8, BMC and DT Swiss, and is also the driving force behind the Callis and the extensive laboratory tests that underpin its development. Avona already has a competitive 700c gravel bike in its range in the form of the classic Callis. The Callis 32 is the logical next step in its evolution – and sets itself ambitious goals.

Why 32 inches?

At Avona, they were sceptical at first. Do we really need 32-inch wheels? Larger wheels mean less scope for geometry, more aerodynamic drag, more toe-overlap and more weight, which has to be offset by costly investments in lightweight construction. The frame requires longer forks and longer chainstays, which increases the wheelbase and detracts from the riding experience.

However, 32-inch tyres can also noticeably improve handling and grip off-road. The result: greater confidence on difficult terrain and the ability to maintain higher speeds through slippery bends. Comfort is also enhanced thanks to improved roll stability. We’ve already put this to the test ourselves with the Chiru Veldt to see how it works in practice.

The tests: wind tunnel and virtual elevation

Avona has based the development of the Callis 32 on two pillars: Wind tunnel tests carried out in the GST wind tunnel, which we also use for our wind tunnel tests at our sister magazine, TOUR. And field tests using the so-called Virtual Elevation Method (also known as the Chung method), which provides an approximate measurement of the resistance encountered whilst cycling.

The result: 32-inch wheels outperform standard wheel sizes – with the same tyres (Schwalbe G-One RX, 50 mm) and at the same speed – in some cases by a significant margin. The rougher the surface, the more clearly the giant wheels demonstrate their superior rolling resistance. And the aerodynamic disadvantage of 32-inch wheels is less than expected, even at high speeds. Avona cites a saving of around 8 watts, depending on the surface, at just 20 km/h, and as much as 12 to 13 watts at 35 km/h. This would result in a significant advantage, particularly in gravel races. The victories of Robin Gemperle at the Unbound Gravel on 32-inch wheels, and of Leon Kaiser at the UCI gravel race as part of Sea Otter Girona, also support this. You can read our own fact-check on the subject of 32-inch screens here.

Faserwerk Kornkreis: Its own 32-inch wheels

32-inch standard wheelsets have been in very short supply so far. To fit the Callis with tyres, Avona also relies on its own brand, Faserwerk, under which Avona develops its own carbon wheelsets, handlebars, seatposts and chainrings. The Kornkreis wheelsets feature a 42 mm rim height and a 27 mm internal width; they are handcrafted in Germany and are available with DT Swiss 240 or 350 hubs. They thus complement the as yet limited availability of standard 32-inch wheelsets. Alternatively, Avona offers the Callis aincluding high-profile carbon wheels from Newmen to.

Faserwerk 32-inch wheels:

Designed to suit younger riders too: the geometry

One of the most unusual features of the Callis 32 is that it is designed to fit riders from 164 cm in height. This is by no means a given for a 32-inch bike, as larger wheels generally leave less scope for compact geometries. Avona solves this problem with a special geometry concept. Every frame size can be ridden in both a traditional and a forward-leaning position. The difference lies in the seatpost:

• 30 mm offset + short stem → classic riding position, effective seat angle 74°
• 0 mm offset + long stem → progressive forward riding position, effective seat angle 76°
• A 15 mm offset seatpost is also available as a compromise option

In the forward riding position, smaller riders can often ride a larger frame size – which in turn allows for lower oversize versions of the stack measurements. The result: according to Avona, the Medium frame is suitable for riders from 164 cm upwards, with the lower limit depending on the preferred riding position.

An overview of the geometry (with a 30 mm offset strut)

The 70° head tube angle has deliberately not been set too flat: as larger wheels increase the trail anyway, a flatter angle would have made the bike too sluggish. With a 60 mm fork offset, Avona keeps the trail at a manageable 82 mm – sporty yet stable.

As aerodynamic as possible: frame and components

Unsurprisingly, the Callis’s frame and fork are aerodynamically optimised to minimise the bike’s drag as much as possible. The carbon chassis has the following key specifications (manufacturer’s figures):

• Frame weight: 898 g (painted)
• Fork weight: 409 g (painted)
• Complete frameset including all parts: 1,728 g
• Ground clearance: up to 55 mm (with a 6 mm safety margin)
• Stiffness vs. Callis 700c: +7 per cent torsional stiffness, +12 per cent BB stiffness, same vertical compliance
• UDH interface (Universal derailleur hanger)
• Only Single crank
• Flat-mount brakes, 160 mm standard, 180 mm optional
• Integrated Frame storage compartment
• Two large bottle holders still fit
• Boost chain line, 12×148 mm at the rear, 12×110 mm at the front
• Ground clearance a maximum of 55 millimetres
• Enduro 440C stainless steel steering head bearing with a lifetime guarantee

Models and prices

Avona offers the Callis 32 in three configurations and as a frameset. Avona fits CeramicSpeed UFO Wax chains to all models.