Argon 18 Nitrogen Pro review: A modern aero package but it badly needs a change of seatpost

We first saw the new Argon 18 Nitrogen Pro back in August 2025 for a wind tunnel test when we had a paintless, lacquerless, menacing looking thing that seemed fresh off the factory floor. It was somewhat overshadowed that day by us also having a prototype version of the Factor ONE in the tunnel (yes, we were very smug), but nevertheless it caused enough of a stir at the time and hence to have at least piqued my interest.

Fastforward a year, and in order to review it properly, I took it on an extended trip home to Cornwall to see my family, where I sniffed out some familiar roads to calm my soul on the clifftops, and a few fresh sections to hunt out rare flat roads, where it does tend to shine. It is a fabulous place to ride, but absolutely murderous if you want an easy day out.

Reviewing it as I did straight after hopping off the fabulous Look 795 Blade RS - to be published in the coming days - left it with a tough act to follow, and one it didn’t quite manage to live up to. It certainly isn’t without merit though, and while I don’t necessarily think it’s quite up there with the absolute cream of the best road bikes (or indeed the best aero road bikes), it is certainly a good bicycle, and may well suit your tastes more than it does mine. Ultimately the front end felt a little languid for my tastes, but more presingly the combination of a slack-ish seat tube angle and a 20mm setback seat post stuck me in what felt like a rather old school position out of step with the modern era.

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Design and aesthetics

As always, let's tackle the subjective subject of how the thing looks first; I’m a fan. It manages to toe the line of looking hyper-modern without going absolutely bananas like the Factor ONE, with clear cues from TT bike design. Those hefty, extremely dropped seat stays would be just at home on the brand’s triathlon machines. Ridley also helped everyone out by normalising massive headtubes with the Noah Fast 3.0, something the Nitrogen Pro has up front to go with a relatively wide-set fork that’ll handle 34mm as measured tyres, which is a capacity matched at the back end.

While it can handle a 34 it comes with 30c Vittoria Corsa Pros on Scope Artech 6.A wheels, but not the standard set that I had the pleasure of riding on the Look Blade; these are a collaboration with Scope and Atten, Argon’s in-house componentry brand, and the extremely fast wheels have been reshaped to better suit the 30mm tyres and to better interact with the frameset, all while keeping the Scope hubs and that eye-catching fish scale texture. In reality they feel no different to the standard Artechs, but it is heartening to know they’ve at least been optimised to this machine in particular.

Back up front and you get the same CHB-01 cockpit as is found on the brand’s Anti Matter aero gravel bike that my colleague Tom loved so much. This you can spec when you buy it in either a 36cm or a 38cm width, and with a choice of stem lengths from 80-130mm at no extra charge.

What you cannot do is spec a zero offset seatpost, which is something I believe you should not only be able to do but also something you should do. I’ll go into the why in a sec, but if you do want to do this it’ll cost you a cool £225.

Geometrically I do want to start at the back end. The seat post is pretty set back; 1 full degree slacker than the Look Blade. This is compounded by having a full 20mm setback seatpost, rather than a 13mm on the Look. It is the same as on a Tarmac however, though again with a less severe seatpost setback from Specialized.

Without boring you too much with maths, for my saddle height a 1 degree change in seat tube angle (STA) equates to roughly 13mm of increased saddle setback. Add in the 7mm differential in the seat posts and the Argon puts me a full 20mm further behind the BB; potentially manageable if you run your saddle in the middle of the rails but as someone who has theirs slammed forwards I would have needed a costly swap.

This is all compared to somewhat ‘normal’ geometry bikes. The seat tube angle is 1.5 degrees slacker than a progressive Ridley Noah, and a full three degrees slacker than the Factor ONE, though these are a lot more radical and not everyday machines.

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Before I jump two-footed into the aerodynamics, it’s worth remembering the Nitrogen comes in two guises; the Pro, which I have with a lighter, stiffer carbon layup and more pricey build options, and the standard model with lower tier components and carbon, but ultimately the same aerodynamic shape.

With a rider on, at the time of testing it proved to be reasonably fast. Since then, though, we have been fortunate enough to test a load of other new releases, and it isn’t quite as fast as many of them, now sitting around ⅔ of the way down our power rankings of road bikes. While you should obviously read all of our wind tunnel content, and the one pertaining to the test in which the Nitrogen Pro was included, it’s worth bearing in mind that while ‘bottom third’ sounds bad, it is only shipping 7.5 watts to a Cervélo S5 in reality. If you need every watt then this may be of concern to you, but it’s perfectly plausible you could make this up elsewhere, though you could also make up that deficit elsewhere and have a faster bike.

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Performance

It’s easy to perhaps look at ‘bottom third in the wind tunnel rankings’ and conclude that this is a slow bike, but it isn’t really. Seven and a half watts is measurable, though only barely perceptible, and on the flats the Nitrogen Pro feels very much at home once you settle into a decent position, though as with so much of the performance of the machine the thing that seems to be holding it back is mostly down to the position it puts you in.

Having a relatively slack seat tube angle combined with a 20mm setback post means you do feel like you’re hanging off the back of the bike. On the flats, while the bike is certainly aero enough, it lacks that feeling of efficiency that comes with being more over the front of the bike. My hips felt impinged, and more than anything else it just felt quite old school.

On the flat it lacked that feeling of biomechanical efficiency (though it felt aerodynamically so), and on the climbs where your weight is naturally going to be further back I felt I had to spend more time on the tops than in the hoods just because that’s where my weight fell. When out of the saddle, either on climbs or in a sprint, these problems dissipated immediately, but that isn’t a sustainable solution. A shorter stem may have helped a touch, but only in terms of the overall reach and not what’s going on at the hips. Basically it needs a zero offset seatpost, and I think you should factor it into the cost of the machine.

I don’t think I’m alone; I did a basic straw poll (Instagram stalk) of Argon sponsored athletes. Chris Hall, Rasmus Bøgh Wallin, Linus Østdal, and the riders from Team Cranks appear to be on zero setback posts. It isn’t exclusive, and some other athletes weren’t, but from what I can see from a brief search it seems the majority are opting for the option to get them over the front of the bike.

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Up front I found the fact my weight was off the back more than I’d like, combined with a slacker head tube angle (0.8º slacker than Tarmac, for example) meant the front end felt a little more languid and slow than I’d like, particularly at slow speeds. Moreover, being over the back means less weight over the front wheel, meaning reduced front end grip. This is, again, solvable with a costly seatpost swap, though only to a point; the head angle ain’t going to change. That being said, if you want a road bike that errs towards stability rather than waspish agility then this could well be a machine for you. On the twisty lanes of Cornwall I often found myself wishing I was on something a little more reactive, but on the flip side if you relish longer, steadier efforts on flat or rolling terrain (once you lock the position in) I think this would be a very decent machine.

At 7.5kg in this spec it’s not a superlight hillclimb machine but there’s a lot of carbon in the frame, forks and in those deep Scope wheels. It doesn’t have the immediacy of acceleration on steeper gradients that you get with bikes around the UCI weight limit (or below), but it’s also not absolutely leaden either. Certainly one more for fast, rolling terrain but if anyone tells me they can’t bear to ride a 7.5kg machine in the mountains I will tell them to go and touch some grass.

Sprints… now we’re talking. That super-compact rear triangle with large, boxy stays in combination with a bottom bracket shell that’s tall enough to sit proud of the outer front chainring just gobble up high wattage efforts and there’s no concerning play in the cockpit at all. I’d have like the tops to sweep forward a little sooner; the right angle transition is quite sharp and can sometimes leave your forearms contacting the bars when you're sprinting in the drops, particularly uphill, but it’s a minor quibble, and not something I cared too much about while bagging a few local, extremely low hanging ego-massaging KOMs.

Value

The Nitrogen Pro, in this spec at least, is a funny old beast from a value perspective and is a little like the Force-equipped Factor Elara I reviewed recently. Everything besides the groupset is top drawer and as you would get on the best-of-the-best model, so you can look at it two ways: either you’re getting basically the performance of a £12,500 bike for £9,500 ($10,499), where a saving of three thousand pounds to Dura-Ace is significant, or you can look at it as £9.5k being a lot for an Ultegra-spec bike. An Ultegra Specialized Tarmac (not the S-Works, which this ‘Pro’ Nitrogen is more akin to) is £3.5k cheaper, but has less fizzy wheels, a separate cockpit, and it doesn’t say S-Works on the downtube.

Personally I actually like this new trend of top tier bikes but with a downrated groupset. Aside from weight, Ultegra is basically indistinguishable from Dura-Ace and Force is essentially the same as Red so it saves a huge wad of cash for a negligible performance hit.

Setback seatpost aside, as this is a problem that I think can be alleviated at a small cost, I think it accounts for itself reasonably well. Extremely fast wheels tuned to the frame and tyres, which themselves are a modern 30c width and not a cheaper option to bring the price down. A decent cockpit, and a stiff package that is pretty aerodynamic in the grand scheme of things, even if it isn’t world beating.

Verdict

As tested I think there’s a lot to be positive about with the Argon 18 Nitrogen Pro. It’s stiff, an excellent sprinter, and while the handling isn’t lively enough for my liking it is certainly acceptable if you prefer something a little more stable and forgiving rather than hair raising and spicy. I think it’s a bike that, with a change of seatpost that I think is more of a necessity than an option despite the added cost, would be a fine mile munching fast bike for rolling and flat terrain.

I think if you’re looking for something of a do-it-all fast bike then you will perhaps have a better time with something with more of an all-rounder feel.