At Cervélo we see a need for two distinct types of road bike frames: aerodynamic frames (our Soloist family) and frames optimized for stiffness-to-weight (STW) ratio (our R-family). While the Soloist family is often superior to any other road frame available, there are situations where a non-aero frame is preferable:
- If the UCI weight limit is not taken into consideration, the STW frame and by extension bike can in theory be made lighter for the same stiffness. In practice, the Soloist Carbon is as light as most "superlight" frames on the market and has superior stiffness, but if the Soloist Carbon technology is applied to a frame without taking the aerodynamics into consideration, an even lighter frame would result. That is exactly what we did with the R3. In most situations, the slightly higher weight of the aerodynamic frames is far outweighed by their aero gains, but on rides where the difference is made on the climbs, a high STW frame would be preferable.
- In very rough conditions such as Paris-Roubaix, we can create better tire & mud clearance on a non-aero frame. Especially with the new R3 and R3 Bayonne frames, the increased tire clearance allows Team CSC to run their 27mm pavé tires. In fact, you can even run narrow 28mm cyclocross tires on these frames should you desire to.
The R family started with the R2.5, a frame that was strong enough for the cobblestones of Paris-Roubaix yet also the lightest bike in the Tour de France (as ridden by Ivan Basso and Carlos Sastre). But the R2.5 was a fairly traditional frame both in tube shapes and construction methods, so soon after it was introduced we started working on a new project for the R-family. This became project FM41, and the goal was to design the ultimate STW frame by starting from scratch and not taking any of the current solutions for granted. In other words, although the frame did not have to be aerodynamic, it did not have to be traditional either. It should be designed and engineered with a complete focus on optimizing STW, without any regard for how such a frame would look in the end.
Our first focus was on the tube shapes. From all the different situations one can encounter while riding, we distilled the three most important areas that have an effect on the design:
- the out-of-saddle sprinting or climbing case,
- the descending case,
- the ride quality case.
Each of these cases loads the frame in a significantly different way, ideally requiring different tube shapes and material usage. The problem is how to balance these different loads in the overall design and how to find tube shapes and carbon selections and lay-ups that perform well in all three cases.
The resulting tube shapes of the R3 are very unique, but they are unique for only one reason: engineering. Every shape on this frame, from the Squoval downtube to the super slim seatstays, is driven by the engineering focused on optimizing the STW. Never has a frame been designed with such a singular devotion to solving the STW puzzle, and the test results show this.
At the same time, the seatstays of the R3 not only help achieve this incredible STW ratio, they also provide one of the highest vertical compliance scores ever measured. So with regards to torsional & bb stiffness and vertical compliance, you can have your cake and eat it too.
Team CSC will use the R3 in selected races, mainly on the cobblestones. Team CSC newcomer Karsten Kroon tested an R3 prototype on the cobblestones near his home, and his feedback on the R3 was extremely positive. He always thought his old bike was the best frame for the cobblestones and he couldn't believe how much more comfortable and better tracking the R3 was. In head-to-head tests, the compliance in the R3 seatstays allowed him to keep much better contact with the road than on his old bike which tended to skip over the cobbles.
The combination of tire clearance, vertical compliance and light weight means that Team CSC will be the only team able to get bikes as low as 6.8kg for the classics even with the use of heavier wheels and tires. For most other races, it does not make sense for Team CSC to use the R3 because the bike would be too light. There is no point in riding with a superlight frame and some lead weights under the saddle, better to use those few extra grams of weight to make the frame aerodynamic, i.e. ride the Soloist Carbon. But for those of us who do not have to be concerned with UCI weight limits, the R3 allows for a bike that is not only extremely light, but also very safe due to its stiffness & strength and comfortable due to its vertical compliance. Talk about a win-win-win situation.
Fabian Cancellara made full use of the R3 capabilities and the extra-ordinary compliance of its rear triangle at Paris-Roubaix. Says cyclingnews.com: Like a number of teams, CSC rode on carbon bikes during the race. It was questioned by others before the start, but Riis put his full support behind his director Scott Sunderland. It proved to be the right choice, as Cancellara appeared to be floating over the cobbles and the team only suffered one puncture on the day. Sunderland explained to Cyclingnews that the Cérvelos they used had a box-section downtube and a special chain- and seat-stay design so that the rear triangle flexed more on the cobbles, almost like rear suspension. In addition, the team was running 27mm tubulars with normal spoked wheels. "I have never been that comfortable on the cobbles," Fabian confirmed to the VUM papers. "The frame; the wheels, everything was picobello." Great words of praise for the lightest frame in the ProTour from the most powerful man in the most punishing race.