Aero-focused wheel brand Swiss Side has introduced two new Gravon gravel wheels to its range and given some interesting information on the significance of aerodynamics in gravel riding, including the importance of tyre choice.
A focus on aerodynamics in the gravel market is nothing new, of course – 3T introduced the Exploro as "the world's first aero gravel bike" back in 2016 – but these are the first gravel wheels from Swiss Side. The Gravon 420 comes with 42mm deep carbon rims while the Gravon 250 has 25mm deep aluminium rims.
Swiss Side says that there is "a significant performance advantage to be gained with the right setup" on gravel.
"A typical gravel bike setup has around 40W higher overall resistance at 30km/h [18.6 mph] than a road bike, with this penalty split equally between aero drag and rolling resistance." says Swiss Side. "[You can gain] up to 5W aero drag savings with Gravon 420 aero gravel wheels compared to standard gravel wheels [and] up to 12W aero drag savings just from the tyre choice.
"In a race like the Unbound Gravel 200 [a 206-mile gravel event in Kansas, USA], the right wheel and tyre choice alone can save over 8.5 minutes. To put this in context, the top four riders in 2021 finished within 1.5 minutes."
Of course, that doesn't mean that the fourth placed rider would have won with the right wheels and tyres because loads more factors come into play, but you get where Swiss Side is coming from.
We'll come back to the aero claims in a mo. First, here are details on the two new Swiss Side Gravon wheelsets:
"These 42mm deep carbon wheels take a modern approach to gravel riding: aerodynamically efficient, lightweight, and ideal for racing," says Swiss Side. "With a 24mm inner rim width that allows for tyre widths up to 69 mm, they also deliver minimal rolling and roll-over resistance, as well as optimal traction and comfort."
Wheelset weight 1,611g
Rim type carbon hookless tubeless rim (TSS), 700c only
Rim height 42.0mm
Inner rim Width 24mm
Outer rim Width 32mm
Hub DT Swiss 240 with Ratchet System 36SL, 12/148 mm thru axle, disc center lock. 10,11,12 & 13 speed groupset compatibility with freehub options for Shimano, SRAM and Campagnolo
Bearings Stainless steel
Spokes DT Swiss Aero Comp Straightpull, DT Swiss Pro Lock hidden aluminium nipples, front and rear: Two-cross (1:1 pattern)
Maximum system weight 130kg
Price €1,468 [approx £1,227]
"This 25mm deep aluminium wheelset excels on all gravel adventures as well as on- or off-road training rides," says Swiss Side. "Compatible with tyre widths up to 69mm [the same as the Gravon 420, above], they are the perfect mix to get (and keep you) hooked on gravel riding."
Wheelset weight 1,895g
Rim type Aluminium, hooked, crotchet tubeless TC, 700c only
Rim height 25.0mm
Inner rim width 24mm
Outer rim width 28mm
Hub DT Swiss 370 with 3 Pawl, 12/142 mm thru axle, disc center lock. 10,11 & 12 speed groupset compatibility with freehub options for Shimano, SRAM and Campagnolo
Bearings Stainless steel
Spokes DT Swiss Aero Comp Wide Straightpull, DT Swiss New Aero Straightpull, DT Swiss Prolock Squorx ProHead alu nipples, front and rear: Two-cross (1:1 pattern)
Maximum system weight 130 kg
Price €389 [approx £325]
The Gravon 420 and 250 gravel wheels are available immediately at swissside.com.
Swiss Side says that, as you'd expect, gravel bikes pay a big penalty compared with aero road bikes in terms of drag, especially at higher yaws.
"Aero road bike frame profiles are designed to ‘sail’ and harness the wind for reducing drag, whereas the gravel bike frame in this case [a Cervelo Aspero] has no aero profiles and has a significant ‘anti-sailing’ effect with increasing drag with cross-wind," it says.
"Future gravel bikes will certainly pay more attention to cross-wind aerodynamic performance in the frame design."
Swiss Side says that the reduction in drag you'll enjoy by fitting its Gravon 420 wheels will be increased on windier days due to the enhancing ‘sailing effect’ in cross-winds.
Swiss Side also says, "With the lower overall speeds of gravel riding, the effective cross-wind (yaw) angle is on average higher, so the performance advantage from improved sailing effects will be amplified in the real world."
Tyre width is also important. Swiss Side tested wheels with Schwalbe G-One Allround tyres in 35mm, 40mm and 45mm widths, and Continental Terra Speed in 35mm and 40mm widths.
"The results show that increasing the tyre width increases the aero drag and reduces the sailing effect," says Swiss Side, unsuprisingly.
"The measurement data was very consistent with both the Schwalbe and Continental tyres tested. The differences per 10mm increased tyre width, were around 3.6W at 30km/h, increasing to almost 12W at the higher speed of 45km/h."
Of course, tyre choice isn't just about aerodynamics. You'll want to consider grip, comfort and rolling resistance too.
Knobs and treads are important for grip when riding off-road but Swiss Side says, "In general, the rougher the tyre and the size of the knobs, the higher the aero drag and, in particular, the sailing effect is reduced.
"However, the Continental Terra Speed was a slight exception with a low aero drag level and relatively good sailing effect for its comparatively large sized knobs... The Continental Terra Speed tyre would appear to be a good choice in terms of compromise between aero performance and grip on loose surfaces."
As mentioned, you can check out the full report here.
Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been road.cc technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now pushing 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.