Wind tunnel testing aero bikes: Wild Factor prototype, Colnago Y1Rs, Cervelo S5, Ridley Noah and eight others compared in our biggest aero group test yet

Last month, the Cyclingnews tech team returned to the unassuming industrial unit that is fast becoming our second home: the wind tunnel at Silverstone Sports Engineering Hub, for the latest in the CN Labs series of empirical group tests, and this, I think, we can call "the big one."

We tested 12 of today's best aero road bikes. Not the aero all-rounders like the Tarmac SL8 or the Madone as tested last year - check out last year's superbike test here - but purebred aero machines with headtubes inspired by the Mariana Trench and radical silhouettes that, in the case of some, probably make Eddy Merckx's eye twitch with contempt.

This included Tadej Pogačar's steed of choice, the Colnago Y1Rs; his big rival Jonas Vingegaard's Cervélo S5; the Ridley Noah Fast 3.0 with its mega deep head tube; that crazy Factor UCI-legal pre-production prototype; and the Argon 18 Nitrogen Pro that didn't exist until this week.

The full list of bikes is as follows:

• Argon 18 Nitrogen Pro (pre-production prototype)
• Bianchi Oltre RC
• Cervélo S5
• Colnago Y1Rs
• Cube Litening Aero C:68X
• DARE Velocity Ace-AFO
• Elves Falath EXP
• Factor UCI-legal pre-production prototype
• Merida Reacto 9000
• Ridley Noah Fast 3.0
• Scott Foil RC
• Van Rysel RCR-F
• And our baseline: My very own 2015 Trek Émonda ALR

Each bike was tested under three different protocols, including both with and without a rider, as well as with its own wheels as sold and a standardised pair. Tests were performed at fast amateur road race speeds, across a range of yaws, and with each bike set up to a matching position designed around our test rider.

The resulting feature, all 12,000+ words of it, is exclusive to Cyclingnews members, so I won't give too much away here, but a special thanks must go to every single one of you.

I've said it before, and I'll say it 'til the cows come home: your subscription fee is the only thing enabling us to do these tests, so thank you.

If you're already a Cyclingnews member, you can head to the full test to see our protocols and find the results.

And if you're not, you can get a trial month for just £1 / $1 / €1.

A teaser: What did we learn?

More than anything, we learned that the crazy Factor prototype isn't all bark and no bite.

Visually, with its forward-protruding wide-set fork, bayonet-steerer tube and ultra-deep head tube, it screams "I'm fast" as loudly and persistently as an angry little Terrier that shouts at anyone who'll listen. But whereas little Terry might run away at the first sign of conflict, Factor's bike has the aerodynamic clout to back up its aggressive looks.

It landed top of the pile by a resounding margin in both of our bike-only tests, and fell shy of the winner by less than a tenth of a watt (well within the error margin of our test) when tested with a rider.

Elsewhere, there's a new definition of 'two-speed peloton'. Bikes designed before the UCI changed its rules around tube depths and compensation triangles are consistently slower than those designed since.

Related to the above, there's an obvious trend in aero bikes towards chunky head tubes. The Ridley, DARE, Van Rysel, Colnago, Cervélo and Factor are just some of the bikes launched in the past two years, and they all follow this trend.

Less so in the test data but more something that the test highlighted, is that the UCI's decision to permit more aerodynamic frames in 2023, before threatening to ban deep wheels, narrow handlebars and big gear ratios in 2026 in a bid to slow down the peloton is evidence of the governing body's short-sighted approach to rulemaking.