It was at a triathlon, the world championships in Kona, that Cannondale finally let us get up close and personal with their new time trial machine. We had all seen it before, most notably when Ivan Basso raced it in Colorado this summer. But that was always at a distance, with no explanation, no details. What we saw was a bike with some intriguing features, and some ungainly lines.
We sat down for a long chat with Murray Washburn, Cannondale’s Technical Marketing Director, for an in depth discussion about the bikes development and it’s features. What is clear is the bike is a totally new machine, not simply an evolution of the Slice. RS stands for Rocket Ship. It was just the pet name they gave the bike during development, but it stuck. Let’s see if it earns the name.
First up the seat post, yes it is ugly, and even Washburn had to agree it is ‘wacky’. That strange post is actually a great touchstone for the rest for the bike. It was not designed, it was engineered. It was not created to look good in photos, it was created to go fast. The form truly followed the function, and it may not always be pretty, but Cannondale is pretty sure it’s fast.
That seat post maxes out the 3-1 mandated UCI tube shape. It’s not wide, like we expect from an aero tube, but look at it from the front and it is incredibly skinny. So the seat post represents the bike in another way as well. The whole bike is designed to be so skinny you could hide it behind Ivan Basso’s bicep, his left one. It’s that skinny.
Up front Cannondale realized the skinniest they could go was dictated by the fork steer tube. Instead of settling for that, they simply removed the steer tube from the fork. Bearings are pressed into the frame with threaded inserts top and bottom of the fork unit. Without that steer tube the front of the bike is the narrowest on the market, significantly narrower than achievable with a steer tube, and still reaches the stiffness targets Cannondale set.
‘Narrow is aero’, that was the guiding principal behind the bike and it flies in the face of the new aero logic, wider is better. The new wider shapes seen in wheels and some of the latest TT bikes, is to deal with yaw, or cross wind. High yaw angles create negative pressure on the leeward side of the tubes as the air separates from the tube before the trailing edge. Cannondale feels the yaw angles those bikes and wheels operate best in are overstated and as such designed a bike to be fast at zero to 10 degrees, not 10 to 20. Keep in mind, the faster you ride, the shallower that yaw angle. So, to get the most out of a TT bike like this in a cross wind, you need to ride fast.
As expected the bike is full of integration. The brakes are integrated, but exposed, so they are easily adjustable for today’s wider rims and pad swapping. The cables are routed internally, but due to the no steer tube design, pivot with the front end, meaning there is zero binding for both easy steering and smooth cable path.
In contrast to the rest of today’s super bikes, what is not integrated is the front end. While the stem is perfectly in line with the top tube at the end of it is a standard bar clamp. This was a nod to both adjustability and sponsors. Cannondale knows their pro teams and triathletes have other equipment sponsors and they felt no need to get into the bar business and make those relationships more difficult. This front end also gives the bike more adjustability that the existing Slice, which was already one of the best, and it’s all doable with a 5mm torque wrench and basic skills.
A unique aero feature that is completely hidden is the channel that runs the complete length of the sculpted Speed Shadow seat tube. Cannodale found the rear wheel picked up air as it rotated and began to pack that air against the seat tube, creating a high pressure against wheel rotation. The channel gives that air somewhere to go, and eliminates that pressure build up.
All this aero talk is important, and necessary in today’s drag conscious world, but Cannondale is a company that stakes its reputation on ride quality, and one of the special things about the Slice was its SAVE chain stays, essentially a micro suspension that removed the harsh ride TT bikes are famous for. The Slice RS has a completely different system that is supposed to me more aero, stiffer and still deflect to the same degree as the original SAVE stays. The RS chain stays come of the BB in a stiff, vertically oriented rectangle, then rotate as they travel back to the rear axle, allowing them to deflect vertically, helped along by the dramatic kink and lay up of the of the seat stays.
All in all the Cannnodale Slice RS appears to be an extremely aero bike, designed to work in a narrower range of yaw than some of the other super bikes on the market. It’s a combination of radical new thinking, a commitment to function over form, and an acknowledgment that Cannondale needs to put ride quality first and foremost.
While the bike we saw belonged to pro triathlete Michael Weiss and is a late model pre-production bike, Cannondale was not ready to commit to delivery dates, weights, or sizing. Stay tuned to peloton magazine for more details soon.