Originally published on 220 Triathlon
Unless you happen to be particularly fond of wind tunnel charts, bike launches can be a somewhat tedious process. So here, at the launch of the 2015 Cannondale Slice, despite the gorgeous setting in a seafront house on Ali’i Drive in Kona, Hawaii, we’re bracing ourselves for the standard torrent of unexciting aerodynamic information and marketing claims. But it never arrives.
Much to our surprise and delight, Cannondale has taken a different approach to its update of the Slice – the original version of which won Ironman World Championships in the custody of Mirinda Carfrae and Chrissie Wellington – and it’s a much more triathlete-friendly and, more importantly, age-grouper friendly one.
The Slice is a triathlon bike, not a TT bike. That might sound like nitpicking, but it’s an important distinction. A TT bike is designed with an emphasis on aerodynamics and speed, whereas a triathlon bike also has to take into account comfort, fit and the ability to run after the five-plus hours in the saddle for an Ironman bike leg. If you’re riding a 10-mile TT you can, to a certain extent, contort yourself into the most aerodynamic position you can manage and worry about the consequences after 20mins of suffering. If you try the same in an Ironman, you won’t even make it to T2.
The new Slice is designed for comfort, light weight and practicality
David Devine, Cannondale’s product manager for the Slice project has even gone so far as to describe the bike industry as having ‘tunnel vision’ when it comes to bike design, becoming obsessed with wind tunnel performance often at the expense of other factors like comfort, handling and weight. Which is why Cannondale has adopted a more balanced approach to performance that it’s described as RealTri technology, with the tag line ‘go faster, stay fresher, ride easier’.
If you check out the chain and seatstay designs on the Slice, you’ll notice how skinny they are and how much more they have in common with road bike stays than other tri bikes. This was a big design decision for Cannondale, because vertical seatpost designs don’t have as much scope for flex as slanted ones on road bikes, so the comfort has to come from somewhere else. The thin profile of the stays also means that, although they’ll sacrifice some aerodynamic benefit, you’ll gain an awful lot in comfort, as they’re ultra-compliant and have a far greater range of deflection.
The design is called Aero Save Micro-Suspension and allows for between 2.5mm and 4mm of deflection under increasing loads. What that translates to for the rider is a bike that feels a lot smoother, to the point where Cannondale makes the bold claim that the Slice is actually more compliant than a lot of endurance road bike frames on the market.
The new Slice's comfort is all about smoothing the transition from saddle to two legs
The comfortable back-end is paired up with the Aero Save fork, complete with offset dropouts and a directional carbon layup similar to the one used in the SuperSix Evo frame. It’s significantly less stiff than the old Slice’s fork, but has a higher stiffness-to-weight ratio and so should offer a pleasing compromise between precise handling and comfort.
Moving on to the frame design, Cannondale has used Truncated Aero Profile (TAP) tube shapes. These are basically aerofoil tubes rounded off at the back instead of following through and finishing in a point. This provides a double advantage of keeping the weight down and providing less side surface area for the wind to hit, making the bike more predictable in crosswinds.
The thinner tubes have been designed to produce a perfect balance between aerodynamics and handling in the crosswinds
Weight-wise, Cannondale has done an amazing job of making the high-mod version of the Slice frame just 1,020g, lighter than many road bike framesets. Of course, the truncated tubes do mean that the Slice loses out in the wind tunnel to the likes of the Specialized Shiv or Cervélo P3, but the losses aren’t as huge as you’d think and come down to fewer than 10 watts of drag at a zero-degree yaw angle.
To put that in perspective, the difference between a rider on the bullhorns and in the aero position is far greater than 10 watts – having the ability to get into a sustainable position is, in reality, far more valuable than stressing over the drag of the bike that you’re riding. Given that the rider accounts for roughly 80% of the drag, quibbling about a few watts really is by the by unless you’re fast enough that such marginal gains matter.
Another nice touch is that every model of the Slice, from the top-of-the-range Black Inc right down to the Shimano 105 version, comes equipped with 25mm tyres for an added bit of comfort. Even better, they have clearance for up to 28mm, so you can go really big if you want yet more comfort. With most recent wind tunnel tests suggesting that there’s certainly no aerodynamic loss from using 25mm tyres rather than 23mm (and possibly even some gain), there’s no reason to go as thin as possible.
Fit and geometry
From a triathlete’s perspective, fit is possibly the most important aspect of a tri bike. A machine that allows you to stay comfortable, aerodynamic and produce the optimal amount of power over the gruelling bike leg is the ideal that everyone is striving for.
With that in mind, Cannondale took the data from thousands of bike fits undertaken by their partner, Guru, on real triathletes – that is, age-groupers and not just pros – and analysed them, using that data to dictate the geometry for the Slice. The result was what they call ‘real tri geometry’, optimised around a steep 79° seat angle that gives an effective range of 77-81°. That geometry aims to enable riders to find the best combination between an open hip angle, an aerodynamic position and comfortable weight distribution.
Cannondale analysed typical seat angles in triathlon when designing the new Slice
Added to that, every model of the Slice comes with a low bottom bracket and short cranks – 165mm for 44-54cm frame sizes and 170mm for 57-60cm – which allows the hip angle to open out further and also has the side-effect of creating a lower centre of gravity and therefore delivering handling that’s even more stable. The other by-product of the lower bottom bracket/short cranks combination is that both the seat height and the stack height move down, meaning the rider is already more aerodynamic.
Frankly, it’s a pretty bold move from Cannondale because it’s going against the trends of almost all its competitors and rivals. It’s relying on the bike-purchasing public to buy into this philosophy in the face of contrary information from countless other big brands.
Our test route starts down Ali’i Drive, turns up Palani Road and out onto the Queen K Highway. It’s an out-and-back that takes in large parts of the Kona bike course and, combined with the 35˚heat and 85% humidity, promises to be a pretty uncomfortable experience. But still a classic Kona race day, weather-wise.
The test bike is the high-mod Dura-Ace Di2 edition with the 1,020g frame. Straight away we notice how astonishingly light the bike feels. Weight-wise it’s genuinely akin to riding a road bike and accelerations are rewarded quickly and dynamically. This transfers over into manoeuvrability as well: the subtle little movements that you get used to on a road bike – like flicking round a pothole or changing line sharply – which are usually markedly less sure on a tri bike, are more than confidence-inspiring on the Slice, if not quite at road bike levels.
The short, steep climb up Palani Road is a test for a tri bike, as most tend to err on the side of frustrating when the gradient kicks up at a level you can’t cope with on the tri bars. But this is another area where the weight of the Slice is noticeable, and it never feels like you’re dragging the bike with you. That’s not to say that we’d necessarily choose to ride uphill on it, but first impressions are that if you were doing a hillier race and wanted to ride a tri bike, the Slice would get the job done and done well.
Out onto the fast, flat terrain of the Queen K and the stability of the Slice really becomes noticeable. It’s a large open space where the wind gusts hard and, even though the test bike was kitted out with deep-section Vision Metron 55 clinchers, the smaller side-on cross section of the bike makes it comparatively easy to handle.
The Slice's stability and road-bike style handling avoid rides getting too tense
As Cannondale alluded to in its presentation, we suspect that when it comes to straight-line speed the Slice does give something away to competitors, like the Cervelo P5 or Felt’s IA. That’s purely subjective based on the speeds we were travelling and the feel of the bike at those speeds, but in the UK, where conditions can be windy more often than not, we speculate that a lot of triathletes might opt for something that could assure them of an easier ride when the weather turns rough.
Comfort was the big factor we were keenly aware of, given Cannondale’s claims about the smoothness of the ride, and we were rather impressed after the 2:30hr test. On flat, smooth roads pretty much any bike can feel comfy, but the hard shoulder of the Queen K can often resemble a demilitarized zone from the amount of debris there is lying around. The Slice handles it all superbly, even when hitting bumps in the road that jolt you to your core.
The seatpost is noticeably subdued, with zero teeth-chattering moments – not something we can say of many tri bikes. Too many manufacturers seem to forget that a triathlon bike ride is followed by a run, so it doesn’t matter if you have the most aerodynamic ride available when you’re sat at the side of the road contorted with back spasms 15mins after leaving T2. Given the choice, we’d go for comfort every time.
Ultimately, we’d like even more riding time to deliver a definitive verdict on the Slice, but our first impressions were fantastic, and we can’t wait to get our hands on one again and chew up more miles over English roads.
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