Wilier TwinFoil frameset

Whoosh! There you go. That's my review distilled into one word – the new Wilier TwinFoil is one fast bike.

Although when viewed from the side the TwinFoil looks vaguely similar to a bunch of other time trial bikes, the front end is very unusual and the frame boasts several innovative features all designed to reduce drag and maximize your speed. Even as pro-level TT bikes go, this is seriously quick.

First up, though, there's that front end. What's going on there? Essentially, instead of a standard fork where the legs meet at the crown, these legs – Wilier call them 'flow stabilizers' – extend right the way up to the stem. Well, I say 'stem' but it's not a stem in the conventional sense; it's really a part of the fork.

Is this making sense? Maybe not. Okay, so you've got a headset at either end of the head tube but the fork legs keep on going upwards outside of the head tube until they join with the stem that isn't a stem. That should clear things up perfectly. Hmmm!

The flow stabilizers (the extended fork legs, remember?) sit forward of the head tube and much wider – there's a small gap between each of them and the head tube. The distance from the outside edge of one to the outside edge of the other is a whopping 68mm. That sounds like a helluva distance when common sense would say that skinnier equals faster in the world of aerodynamics. Surely, the smaller the frontal area the better, yet Wilier have made the front end super-wide.

Here's the rationale, in Wilier's own words:

'Aerodynamic design is about much more than a bike's frontal area. It's really about airflow management: developing a frame and fork capable of directing airflow through and around body parts as well as components and wheels. The most advanced aerodynamics and fluid dynamics studies have led us to measure turbulence in terms of resistance. That is why we chose to name the two airfoil elements that comprise the fork as 'flow stabilizers', each of which boasts an aerodynamic profile that diminishes air turbulence and directs passing airflow in an efficiently linear trajectory.'

Get that? Basically, the idea is to create as little turbulence as possible in order to reduce resistance and maximize speed. Simple. Kind of.

The fork legs – the lower sections – are incredibly deep, as much as 70mm from front to back, and the arms of the linear-pull brakes are effectively integrated into the back of them.

Moving backwards, the frame is made from Wilier's top-end 60 Ton carbon and the tubes have narrow but deep profiles. The rear of the seat tube is slightly cutaway to manage airflow over the rear wheel, a feature common to most TT bikes these days, but the back end is unusual. The seatstays are widely spaced like those flow stabilizers up front – again, to get them as far away as possible from the air turbulence caused by the wheel – ducking in towards the seat tube at the last minute.

The seat post follows the aero theme with its narrow/deep profile while the binder assembly is hidden within the frame so it's out of the wind. As well as being able to slide the saddle forwards and backwards along its rails in the usual way, you can alter the position of the clamp on top of the seat post by 30mm to alter the effective seat angle further.

The rear brake sits just below/behind the bottom bracket and it's shrouded in its own smooth, carbon cover while the cables run internally, the rear mech one exiting towards the end of the chainstay Di2-style. The exception is the front brake cable; that one's external.

One other clever little feature that's worth mentioning is the rear dropout design. Wilier wanted vertical rather than horizontal dropouts for ease of use. The Lampre-ISD pro team use the TwinFoil in time trials and they needed a system that allows for quick wheel changes if one of the riders gets a flat out on the road, so Wilier came up with their adjustable vertical dropouts.

Each dropout is held in place by two Allen bolts and you can slide it back and forth in the frame to adjust the distance of the tyre from the seat tube. Once set, you use the dropouts as you would any other vertical dropouts, so you get the best of both worlds here.

Okay, that's plenty of tech information to be going on with. You get the picture. Wilier have been busy here developing a brand new frame that slips through the wind with minimal turbulence. And if worries about whether or not it's UCI-legal are keeping you awake at night, fear not! It has a UCI approved frame sticker and everything. You can't get any more UCI-legal than that.

The TwinFoil comes as a frameset rather than as a complete bike: that's the frame, the fork/stem, the seat post, the brake callipers and a handlebar spacer (I'll explain that in a mo). That lot will set you back £3,750. Yup, £3,750. Look, we never said it was cheap, did we?

UK distributor ATB Sales built ours up with a Shimano Dura-Ace groupset, Vision cockpit, Zipp 808 wheels with Vittoria Corsa Evo CX tubs and a Selle San Marco saddle. If you were to want a similar build it would cost you about £9,000, making this the most expensive bike we've ever reviewed on road.cc.

I stuck some Dura-Ace pedals on too and it weighed in at 18.17lb (8.26kg), which is a bit lighter than the Trek Speed Concept 9.9 that we tested last year. Wilier claim a weight of 1,320g for the frame, although weight is hardly the main issue here.

The first hurdle is always to get the bike set up as you want it. Your own body causes far more drag than the bike itself so the slipperiest frame in the world is no good if you can't get the right body position.

There's a decent amount of adjustability here. I've already mentioned the fore/aft movement to the saddle; you also get the choice of either a 60mm or 80mm stem (which is really part of the fork system). And on top of that, you get the handlebar spacer, which is a gizmo that clamps onto the base bar to give 47mm of vertical/horizontal adjustment.

I managed to sort out a position with which I was happy. Most of my races are middle distance triathlons (1.2-mile swim, 56-mile bike, 13-mile run) and I set myself up in an aero position that allowed me to stay comfortable through the bike section of that. It's usually a compromise between comfort and speed; chances are you'll be able to play with the variables enough to get where you want to be.

Out on the road, the Twin Foil is incredibly fast. Crazy fast. It just seems to slide through the air like a wet bar of soap through your fingers. We haven't got a wind tunnel here at road.cc so I can't put a precise figure on it, but my times over regular routes say that this is a super-quick bike in the same league as the Trek Speed Concept we reviewed last year. That's anecdotal evidence, of course, and there are a million variables to take into account, but I was getting comparable times for similar levels of effort. I wasn't quite as fast as I was on the Speed Concept, but I was close enough for the difference to be explained by differences in conditions, my level of fitness and so on.

I did wonder what the handling would be like in a sidewind. What would happen when the wind caught that additional material up front? Surely, it would affect the steering. Well, if it did, it wasn't enough to be noticeable. I didn't feel I was struggling any more than usual with gusts from an angle. I mean, any deep-tubed TT bike is a bit of a handful in blowy conditions, but the TwinFoil was no worse (or better) than many others in that respect.

One thing I would say about the front end is that it's firm. With a standard fork and stem, there's quite a lot of opportunity for vertical flex. If you hit a bump, the bars can move a little to take the sting out of things. Here, you have a stem mounted directly on top of a fork steerer and two widely set flow stabilizers. When you hit a bump there really ain't much chance of it dispersing.

That means you're very reliant on comfy armrests to keep the front end comfortable. Vision's gel pads are good and the armrests – the cups they sit in – are bolted to the bars at just one end so they provide a small amount of suspension. If you think the TwinFoil is the bike for you I'd advise you to get something similar. Wilier provide a number of small adaptors that allow the use of most TT bars.

The upside to that firmness is that the steering is bang on. That's a real bonus. I found myself confident enough to stay down on the extensions through corners that would usually have me sitting up and using the base bar, and that has to be good news for shaving off the odd second here and there.

There's virtually no front-end sway when you get out of the saddle – not that you'll be getting out of the saddle all that much on a TT bike, but you're bound to from time to time. The TwinFoil is actually a very good climber. It's not up there with a lightweight road bike, obviously, but it's feathery for a deep-tubed TT bike and it doesn't feel at all sluggish when the terrain heads upwards. It's almost as stiff through the centre as it is up front too, largely thanks to a big slab of frame around the press-fit bottom bracket, so power transfer remains direct when you stand up on the pedals and give it the beans.

One final thing to mention is the manoeuvrability. The TwinFoil has the turning circle of a small bus because the flow stabilizers limit the amount you can move the bars. However, in practice, that's not an issue out on the road. When you're travelling at speed you'd never want to turn that sharply.

Verdict

Super-slippery, pro-level time trial frameset that's stiff, lightweight and comes comes with a pro-level price tag too