FiftyOne Sika Review

They call me the Sika, I’ve been riding far and wide…

Words James Spender Photography Joseph Branston Cyclist Magazine

My kingdom for an AI bot that can tell me every bike’s maximum tyre clearance. But until such time please accept my manual digging, which has turned up only four non-custom road bikes on the market with 40mm tyre clearance: the BMC Roadmachine 01, the Specialized Roubaix SL8, the Enve Fray and this, the FiftyOne Sika. But where the Roadmachine 01 has slack geometry, the Roubaix has suspension and the Fray has mounts, cubby holes and only clears 40mm with a 1x chainset, the Sika sits in a whole new category of its own: a stiff, lightweight racer with sharp handling and very fat tyres. It shouldn’t work, but it does. And I think bikes like this are the future.

Design and fit

‘The Sika is our interpretation of what a modern road bike should be,’ says FiftyOne’s founder, Aidan Duff. ‘It takes the responsive nimbleness from our custom range and combines it with a realistic stack height.’

By ‘realistic’, Duff means the Sika has a taller front end than most WorldTour-esque race bikes, an idea based on the data gleaned from some 500 bike-fits performed by FiftyOne in the custom side of its business. It’s a sound rationale, and one I’ve heard before from framebuilders such as Parlee and Isen through to big brands with fitting programmes such as Specialized.

This higher front end (stack height on this large/56cm frame is 578mm) is disguised to a degree by a fork crown that by my squinty measuring is around 15mm taller than a typical fork. That raises the front end to where FiftyOne wants it without elongating the head tube (which measures 150mm) or adding ungainly spacers.

The overall effect on fit is a bike that feels cruisy on the hoods and has a less aggressive but more sustainable position in the drops. It’s a simple win – make drops more useable by raising their height relative to the rest of the bike – but it’s clever in that the Sika offers another riding position beyond a lot of race bikes, because riding in the drops is comfortable and hence sustainable. I often found my hands had drifted to the drops without giving it much thought, which is a sign of good ergonomics.

That said, the Sika isn’t a relaxed bike. FiftyOne’s geometry ethos (born of Duff’s experience as a ProConti racer) is to make a bike’s trail quite short but its wheelbase quite long. Again, the rationale makes sense. Short trail means a bike reacts quickly to steering inputs; long wheelbase makes the bike more stable at speed. Of course, you could go too far either way, and there is more than one way to skin a race bike, but the angles FiftyOne has opted for – 58mm trail (with 34mm tyres) and 1,010mm wheelbase – combine brilliantly. The Sika is incredibly stable at speed and deft and quick in turns, and I can verify this in part by some new Strava PBs.

I have one winding descent I regularly use to ascertain how fast a bike is downhill, and on the Sika I clocked two PBs over a couple of rides, my average speed now up from 43.4kmh to 47.2kmh. However, geometry is not the only well-thought-out thing here, and it’s only half the speed equation.

Neat touches and bold ideas

Before I let you into the Sika’s not-so-obvious secret, a few more bits of housekeeping lest I sell this bike short. The BB is T47 Inboard,so the BB shell is about as wide as can be for stiffness and splaying the stays for tyre clearance, plus it has all the benefits of threaded bearing cups. The mech hanger is Sram’s UDH, or ‘universal derailleur hanger’, a part designed to unify this most esoteric of components. The bars are FiftyOne’s own design, one-piece, carbon, insanely stiff – like, no give at all – and available in 20 sizes to accommodate the fact that one-piece bars are less adjustable. The bars’ hose routing and clamping is such that removal for packing and reassembly is really very easy.

The seat binder is a classic collar, with Duff lamenting how many times he’s lost a wedge- type clamp down a seat tube. The tube profiles are borrowed from NACA designs, a kind of aerodynamic playbook of slippery shapes used in the aviation industry (NACA stands for National Advisory Committee for Aeronautics). So while the Sika hasn’t seen the inside of a wind-tunnel, its deep head tube, semi-truncated down tube and square-backed fork legs are more than just design flourishes.

The frame itself weighs a claimed 695g (medium) and an uncut fork 350g, which puts this bike firmly in the lightweight category. Yet all of this pales into insignificance when you consider the Sika’s secret: its huge 40mm tyre clearance.

Tyre and mighty

My test build came specced with 34mm Corsa N.ext tyres set up tubeless. On the Zipp 303 Firecrest rims (25mm internal width), those tyres come up closer to 36mm, which is frankly monstrous for what could otherwise be a climber’s bike. Overall weight is 7.29kg, which is laudable given such wide tyres, solid cockpit and deep-section wheels.

Thus, although the stability offered by the geometry absolutely helps in the confidence stakes, and confident riders descend faster, the tyres make this bike.

Using Zipp’s online pressure calculator, I rode the N.exts at the recommended 53psi front/56psi rear (I am anal enough to have a digital pressure gauge) and the result was the smoothest ride I’ve experienced on a rigid road bike (ie, one without suspension à la the Roubaix). As a Vittoria product manager once explained to me, tyres are your suspension, so imagine how much more travel you have with wider tyres, and I can’t help but believe the rationale. That descent I mentioned has an utterly awful road surface in sections, and riding such huge, low-pressure tyres meant I could choose lines based on speed rather than potholes. What a difference it makes to feel like a crap surface isn’t going to throw you off line or split a tyre, or worse.

But more than this, various other segments involving more general, less gravity-assisted riding also proffered PBs, in a way that seemed to happen a few years back when wide, low-pressure tyres first became a thing. It was like I’d become faster overnight.

Perhaps I’m finding correlations where they don’t exist, but I’ve asked enough bike engineers over the past few years and they all state that, like for like, wider tyres have lower rolling resistance. They are faster. They also all agree that wider tyres have a negligible impact on drag save for in the velodrome, and that there is a negligible weight penalty. These 34mm N.exts weigh 340g (claimed), only 40g more than 28mm versions, for example.

Where the Sika gets quicker again, however, is that in moving up to 34mm (again, more like 36mm), it’s taken the reduced rolling resistance and gone faster again thanks to increased grip and the rider confidence it fosters, from cornering to braking. On that last point, all that rubber in contact with the ground makes for exceptional braking, because more power can be applied before the wheels lock up.

The future is wide

I really think the Sika is the future of road bikes, at least if you are a normal human being and don’t live in Switzerland. Real-world tarmac has never been worse; real-world riders never in need of more comfort, so having fat tyres makes sense however you cut it. They increase grip, improve braking, lower rolling resistance and promote comfort and confidence. But the big thing here is FiftyOne has taken these things and stuffed them into what would otherwise be a lightweight racer.

To my mind, this isn’t an all-road bike, although it could turn its hand to a bit of that, I’m sure.
I have every reason to think the Sika would be happy on some pretty decent gravel with some gnarlier 40mm tyres.

Yet this is a bike that wants to be on the road, which begs the question, is 40mm overkill?

Well, as mentioned, this bike running 36mm tyres in practice means it needs more clearance than the current crop of 35mm max-tyre size road bikes. However, I do think the tyres specced here are the sweet spot right now, for this bike and for the type of riding I do. But here’s why the Sika is the future: all it’s going to take is for wheels to get even wider internally, and for tyres to keep up, and the game changes again.

At the moment, most wheels are designed around 28, 30mm or, at a push, 32mm tyres. So these 34mm tyres get dangerously close to having a lightbulb profile on the 25mm internal- width Zipps. Point being, 40mm tyres would be even more lightbulby, which would make them less aerodynamic and more likely to squirm when cornering (fine off-road, less so on it). Then there is tyre choice – so far, no manufacturer really makes lightweight road tyres beyond 34mm. After that, tyres get into overbuilt or gravel territory.

For now, then, 40mm clearance might be unnecessary unless you plan on taking the Sika to some light gravel. But that doesn’t change the fact that the Sika has taken a great idea and run with it, and in doing so has put serious distance between it and the chasing pack. They’ll catch up, I have no doubt, which is why I’ll eat my cotton cap if bikes like the Sika aren’t ubiquitous in a few years.