Last month we noticed that the stage winning bike of Cannondale Factory Racing on stage 7 of the Cape Epic was in fact something different. This shot of Manuel Fumic laying his bike over through a corner highlighted that this wasn’t a standard Cannondale Scalpel. It was something new. And today, Cannondale have announced the release of the Scalpel Si.

A few things stood out – two bottle cages, no external cables, and the shock sat into the frame. We took a punt on the changes already.

We now know that the new bike is the Scalpel Si – and just like Cannondale updated the F29 hardtail with the F-Si, the same concepts have come to the Scalpel platform.

The Scalpel so far

“Back in the day” the Scalpel was a short travel cross-country racing bike. It had no pivot at the rear axle, relying on flex through the composite chain stays to activate the tiny shock placed up high behind the seat tube. It was light and efficient, but a world apart from what you would expect these days.

However, some of the concepts from the original Scalpel remained across the next two iterations, and are now found the Scalpel Si. The biggest thing really is the System Integration (Si) concept. Cannondale really enthuse that you don’t ride a frame, you ride a bike. So they design a frame around building a bike, and consider how each component will work, and how the design can be optimised. Such design has brought us the Si crank set (shown above in an innovate 2×9 setup), the Lefty, purpose built seat posts, stems to match the Lefty – and then a whole front and back geometry tune when Cannondale launched the F-Si hardtail. We took a look at the race spec of James Downing’s F-Si last year.

Building for XXC

Before we go any further, we should consider the ‘XXC’ category that Cannondale feel the Scalpel Si, and F-Si, sit in. Firstly, XXC is basically extreme cross-country. Or the general concept of taking cross-country riding to the extreme, in both a performance sense, and of the actual riding.

So Cannondale want these bikes to push the limits of what is possible with weight, stiffness and geometry. But they also want them to allow the rider to push their limits in cross-country events that have increasingly technically and physically demanding courses. World Cup courses are getting highly technical, stage races like the Cape Epic and Swiss Epic are pushing riders limits.

So cross-country mountain bikes need to change too. Change away from short wheelbases, tight head angles and long stems. And they are making a shift to longer top tubes, shorter stems, slacker head angles, short back ends, routing for dropper posts, and greater frame stiffness for power transfer and better handling.

The Si frame concept

This is simple really. Make a frame that is agile yet stable, and that delivers power efficiently. There are a few ways Cannondale went around this. Firstly, it’s to do with the Lefty 2.0 and the Outfront steering. Cannondale match up a slack head angle of 69.5 degrees (on all sizes) with a long fork rake (55mm offset). This adds up to lots of stability at speed and in rough terrain, especially when it’s steep. However, the large rake also makes a tight trail measurement, the distance between where the axle sits and a straight line through the head tube (along it’s angle), which keeps the handling at low speeds relatively nimble.

Top tubes are long, but standard when matched with other nouveau XC full-suspension bikes. The other end of the Si concept is the rear triangle. On the F-Si Cannondale adopted the 142×12 standard (compared to 135QR) but not Boost. Instead, they chose to move the alignment of the drop outs 6mm towards the driveside. They also then needed to space the chainring over for the right chain line, and dish the wheel back 6mm to the non-driveside so the rear wheel actually tracked behind the front. The same has been done with the Scalpel Si.

Sound crazy? Well it isn’t really. It means the rear wheel can be pulled in nice and tight with a short chainstay length (435mm on the Scalpel Si). Chain line is maintained, which is easy to do with an Si crank. The rear end still has no pivots, and relies on flex on the seatstay, which also means Cannondale have a flat mount disc mount inside the drop out, out of harms way, and allowing the seat stay to flex as it needs to.

The whole back end is super neat, with nice inclusions like a chain protector on the frame.

The frame has a little more going on inside it too. The top tube not only houses the front end of the rear shock, but also the lock out routing, thanks to a custom banjo by RockShox.

Ahead of the shock there is also an internal mount for a Di2 battery, removing the hassle of where to put it. Shimano’s component line PRO offers a head tube mount, but that won’t work with a Lefty and ODI stem. And while tethering it to a dropper post’s stealth line will work with most bikes, frame sizes and posts – it’s not a given, so it keeps it clear of there too.

The swing link on the frame has had a lot of work as well. It’s a neat piece of carbon, and as the stays are part of the suspension action this link is already preloading the shock. Take the shock out, and it will spring back.

What’s also new is the bolt attaching it. To get rid of some hardware, it actually self expands when one side screws into the other. No more little crimp bolts. It is simpler, lighter, and stiffer. All the things Cannondale aim to achieve.

The head tube looks a bit better finished than what we spied at the Cape Epic, although they might have been using covers. There are neat holes that can be filled or open depending on the setup. 1x or 2x, electronic or mechanical, dropper post or not. There are options. It also means whether you’re running moto style braking or right to rear, you can still have a clean setup.

Plenty still remains the same. Cannondale use their BallisTec carbon for superior strength and impact resistance, and the real weight of the medium frame on hand was 2.162kg. That’s with a shock, bottle cage bolts, shock lock out, rear axle, hanger, seat clamp, paint, stickers… a true real world weight. And while the bike has been designed around a 29″ wheel and 100mm of travel, the small size is a 27.5″ wheeled option, as are the XS, Small and Medium women’s models.

Ride impressions of the Scalpel Si

Well we didn’t ride them. We’d like to. But we spoke at length with Manuel Fumic and Marco Fontana, who have been testing the bikes for 6 months.

What they both drew on, was how important it was to get the suspension and geometry right. Neither mentioned weight. While clearly it counts, the efficiency of the bike and the handling is paramount. Fontana was really enthusiastic about how stiff the back end felt when on the gas, or landing jumps and through technical terrain. That said, he did race an F-Si at the World Cup.

They both mentioned how important it was to have spent so long with RockShox getting the suspension tune for the rear shock right. While the bikes use the Full Sprint lock out from RockShox, the shock tune itself is custom. That is essential for getting a short travel bike working right.

There are 10 different models planned for release, 7 of which will be carbon. Interestingly none of them come equipped with a dropper post, but 4 of them come with 2x setups. Stock should be available from your Cannondale dealer in September. If you’re a big Cannondale fan, you will likely love the Scalpel Si. If you’re not – well the combination of ride quality, stiffness, efficiency and stability might win you over.