“Our novel truncated airfoil may look odd and flat, but it is up to 5.84 watts faster than the [outgoing] Terra CLX II, with aero gains that matter from mile one to mile two hundred,” says Roval.
Specialized’s component brand has launched what it’s claiming is “the fastest gravel wheel family ever built”. For the first time it is offering separate aero and lightweight options in response to the discipline diverging. The Terra Aero CLX features the new Chopped Aero Speed Shape which Roval says is equivalent to a 70mm deep rim in the wind tunnel, while the new Terra CLX III weighs a claimed 1,079 grams with valves and tape, and is the lightest in its class according to the US brand.
Here’s the rationale: “The Terra CLX II wheelset established the benchmark for lightweight speed and confident handling across mixed terrain. But elite gravel racing has evolved: courses are faster, riders are stronger, and equipment demands both aerodynamic efficiency and terrain compliance. Oh, and they have to be able to take an absolute pounding and keep air in the tyres.”
So the two new wheelsets are designed to “dominate” everything from Unbound to everyday epics. Roval says they build directly on the heritage of the Terra CLX II, inheriting the low weight, carbon layup and racing pedigree while pushing into new territory with aero shaping, composite spokes, overall wheel durability and “massive improvements” in puncture protection.
Roval Terra Aero CLX
Roval has recognised that gravel racing is being done on rougher terrain with bigger tyres at higher speeds. It doesn’t quote the usual phenomenal average speed of the latest Unbound winner compared to five years ago – everybody gets it. But to sum up, WorldTour-level riders on gravel are hitting speeds where aerodynamics matters – and with riders running wider tyres too, it’s gone back to the drawing board to design what it says is a specific aero gravel wheel that isn’t derived from smooth-road hypotheticals.
Why does an aero gravel wheel need its own rim shape? Because, as British brand Parcours explained when it launched its groundbreaking FKT aero gravel wheel last year, if you were to try to create an airfoil rim behind a 40mm gravel tyre to achieve the optimal 4:1 ratio, the rim would need to be around 120mm deep – which would severely compromise handling and would be very heavy. Parcours used a hybrid truncated virtual foil design that it said “helps to manage airflow from the wider tyre, reducing turbulence caused by the more extreme tread required for gravel”.
Roval seems to have taken a similar approach, optimising the Terra Aero CLX for a 45mm Specialized Tracer tyre, reflecting how wider tyres are become the new normal for racing, with many using bigger tyres even than that.
However, Roval ended up with a very different shape from Parcours – and also from Zipp, whose 303 XPLR launched last year deployed a similar truncated airfoil shape. “The first of its kind, our Chopped Aero Speed Shape tests like a 70mm front wheel, providing aero gains without weight penalties,” says Roval. The front has a rim depth of 50mm and the rear 45mm, and the Roval Aero Composite Spokes by ARRIS are claimed to be pre-shaped for maximum aero benefit. Although it’s optimised for a 45mm tyre it is compatible with 35-60mm rubber.
How did Roval arrive at the very unusual rim shape?
It says the Terra Aero CLX development team began with more than 300 digital rim shapes, each created through multi-factor shape optimisation models that weighed together aerodynamic drag, crosswind stability, hook strength, structural stress ratios, weight minimisation, tyre interface performance (35-60mm). Each model was evaluated not only for pure drag but also for how it performed with real gravel tyres moving through complex yaw angles.
Traditional CFD, it continues, treats the wheel as a standalone object. For the Terra Aero CLX (as with all Roval wheels), CFD includes the wheel matched with a tyre in a frame – in this case the Crux.
The simulations included:
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Airflow around a 45mm Tracer gravel tyre on the Crux bike
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Tyre tread height and turbulence effects
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Sidewall bulge and casing profile
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Bike fork spacing and wheel offset
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Rider’s expected on-course yaw distribution (0-20°)
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Rough-surface micro-yaw fluctuations specific to gravel racing
According to Roval, this whole-system modelling produced insights that do not appear in classic road-based CFD, finding that several shapes that looked fast in isolation produced turbulence at the tyre-rim junction that erased gains. The successful shapes smoothed airflow off the tyre, with the final Terra Aero CLX rim shape delivering the aerodynamic speed of a 70mm deep road wheel while retaining the weight and stability of a shallower gravel rim. Roval notes that its aero gains are especially strong from 5° to 12° yaw, where gravel riders spend most of their time.
The width plays a key role: the Terra Aero CLX uses a wide 38.5 mm cross-section designed to work with 35-60 mm tyres without the flow separation seen with narrower road-derived outer rim widths that lead to the ‘lightbulb’ profile – the rim and tyre are designed to work as a single airfoil, with flow off the tyre shoulder guided by the rim’s larger leading radius. The internal rim width is 27mm and it uses a 5.38mm bead hook. The claimed weight is 1,340 grams including valves and tape.
Roval Terra CLX III
Roval doesn’t spend so much time explaining the Terra CLX III, simply claiming it is “the lightest, most compliant competitive gravel wheelset available”.
“Compliant” isn’t usually a plus point for road wheels, but in the gravel sphere the bicycle and wheel designers are still trying to find the right balance between stiffness and comfort. Stiff is not necessarily good in gravel – it can easily be a negative. That’s why Roval quotes for the Terra CLX III a surprisingly precise 21.52% improvement in lateral compliance for comfort and control compared with the outgoing CLX II.
It has a 38mm external rim width and 27mm internal, and its sweetspot is 45mm tyres. And, like the Terra Aero CLX, it has 4.86mm bead hooks rather than a hookless design for “maximum tyre choice and pressure flexibility”.
The 1,079g weight is very impressive – the Roval Aero Composite spokes by ARRIS (as used by the Terra Aero CLX) save crucial grams here. They’re quoted as being 20% stronger than steel while significantly lighter, with titanium ends.
Specifications
Roval Terra Aero CLX
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Rim depth: front 50mm; rear 45mm
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External rim width: 38.5mm
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Internal rim width: 27mm
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Weight: 1,340g
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Price: £1,299 front/£1,699 rear
Roval Terra CLX III
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Rim depth: 27mm front and rear
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External rim width: 38mm
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Internal rim width: 27mm
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Weight: 1,079g
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Price £1,149 front/£1,599 rear
We have a set of Roval Terra Aero CLXs on test, so keep an eye out for our review.
