The pinnacle of cycle sport is reached, in mechanical terms, when a manufacturer custom builds the machinery of a team’s elite rider. Common place in eras when steel and aluminium dominated the peloton, the prohibitive costs of the tooling needed to manufacture a bespoke monocoque carbon frame makes the presence of such unusual, even in the top-tier.
Cannondale, however, did not blanche at the six-figure investment required to make six bikes for team leader, Peter Sagan - three SuperSix EVO Hi-MOD Team bikes for stage races, and three Synapse Hi-MOD bikes for the Classics.
Sagan’s bespoke Synapse contains all of the technical development of its production sister, but with a radical geometry that stretches even the professional cyclist’s preference for an elongated riding position. “The top tube is basically 4cm longer than normal, and with a very long stem,” says Chris Dodman, a senior engineer in Cannondale’s R&D Division. “It’s an extremely long bike.” He isn’t kidding.
Peter Sagan's custom Cannondale Synapse Hi-MOD. Note the extremely long top tube. pic: Marthein Smit
Cannondale are well used to accommodating the specific requirements of the men who have ridden their machines to glory: the bikes of Mario Cipollini and Vincenzo Nibali are among a magnificent collection displayed at Dodman’s office in Freiburg when Rouleur visits.
While Sagan’s machine is specific, even by the standards of the breed, the custom geometry is arguably the least interesting aspect of a chassis that marks the rapid transition of the ‘endurance’ bike from the status of ugly and unloved sister of the racing thoroughbred to a machine able to place equal priority on comfort and speed – and to command the attention of professional teams.
Dodman admits that Cannondale’s engineers were caught off-balance by Cannondale Pro Cycling’s eagerness to compete on the new Synapse. “We had early development frames that we gave to the team, and they said, ‘Great. We want to race it.’ And we weren’t really prepared.” He chuckles at the memory. “We were ready to roll it out for Paris-Roubaix, but they said, ‘No, we want to race it in all the Classics.’”
Dogs, ponds and helices
“The helical chainstays, when they compress, I liken to a dog getting out of a pond and then shaking itself: twisting, and throwing the water off, and dissipating the energy,” Dodman smiles. “The road vibration, the micro motions of the helical forms of the chainstays, is kind of like the dog shaking the water off.”
Cannondale made a six-figure investment in six custom bikes for Peter Sagan - three SuperSix EVOs for stage races and three Synapses for the Classics. pic: Offside/L'Equipe
He talks of ‘pure innovation' – sea-change development, immediately obvious even to the man on the street – and ‘evolutionary innovation'. The helical chainstays are likely to belong to the latter, inheritors of a legacy begun with the "zero pivot" suspension of Cannnondale’s Scalpel mountain bike.
He credits the "mindbending" skill of industrial designer Erik Eagleman for creating the smooth transitions on which the Synapse relies in large part for its comfort: shapes replicated in 11 sizes, including women’s. The flattened chainstays and seatstays are the latest advance in Cannondale’s quest for rear end compliance: the precise quality cherished by Sagan in the cobbled races of Spring.
“As you sit on the seatpost, the seat-tube flexes, and the seatstays and the chainstays flex, so you get this micro-suspension at the rear axle,” Dodman explains. “When you’re cornering hard, with all your weight on the outside pedal, the micro-suspension gives you traction in the corner. It’s a couple of millimetres, but when you’re at the limit, it makes all the difference.’
Further concessions to comfort can be found in the 25.4mm seatpost, one which attains maximum exposure from a clamping wedge located in the top-tube. Unlike more conventional designs, the seat-tube does not extend above the top-tube.
Ask a team how much clearance they require between tyre and seatstay to prevent stones from jamming the rear brake and they’ll tell you 4mm. Ask them if they’re sure that’s enough, and they’ll tell you 5mm. Ask them how much they really need, and you arrive at 5.5mm. And that, combined with 27mm tyres, mounted to 24mm rims, reduced the tolerance for positioning of the brake pads on Sagan’s Synapse to 1mm. Even using SRAM’s Red caliper, whose circa 51mm ‘drop’ is longer than most of its ‘short drop’ competitors, the pads had to be positioned at the bottom of the slots.
Cannondale have patented the Synapse's split seat-tube design, one accommodated by adding 5mm to the left-hand side of the BB shell. pic: Marthein Smit
“To get that 5.5mm meant that you had 1mm tolerance of the position of the blocks,” Dodman explains. “It was a question of assembling the brakes with the wheel, at the factory, because there is no margin for error.”
The solution to what might have been an expensive miscalculation was to raise the brake bridge to its maximum extent.
“You’re talking about three bikes, with custom geometry. When you talk about the cost of the custom Sagan Synapse, and the custom Sagan EVO, you’re talking about six figures for six bikes, for just the frames. You don’t want to get it wrong and find that you can’t get the brakes on.”
Land of the pyramids
The split seat-tube is the most immediately obvious design feature of the Synapse, and as such perhaps falls into Dodman’s 'pure innovation' category. In any case, it is significant enough for Cannondale to have patented it, a step the brand does not always make, preferring in many cases to rely on the difficulty of copying the design as its own deterrent, or, in instances like the BB30 bottom bracket, declaring it ‘open source’.
Sagan rides his Synapse to glory in this year's E3 Harelbeke. pic: Offside/L'Equipe
To describe the function of the “power pyramid” seat-tube, Dodman draws an analogy with a skier, specifically the skier’s legs. Hit a bump, and he bends his knees. The movement offers compliance and helps to absorb the impact, but can leave him off balance. By widening his stance, however, he becomes more stable.
This theory underpins Cannondale’s decision not only to split the seat-tube at its junction with the bottom bracket, but also to increase the width of the BB shell from 68mm (the standard on previous Cannondale bikes) to 73mm. Critically, the additional 5mm is placed on the left hand side of the shell, allowing for a broader chainstay on the non-driveside.
“If you were to simply do a very wide, flat seat-tube, it could buckle in the middle,” Dodman says. “But if you take that same shape, and split it, and curl the material up into two tubes, you have two very strong structures.” Moving the material 'outboard', he continues, makes it more structurally efficient.
Move to the front end of Sagan’s bike to contemplate the complexities of the fork. Immediately notable is the positioning of the drop out. The fork leg appears to ‘over-reach’ the axle – a development begun with the SuperSix and accentuated for the Synapse, whose greater emphasis on comfort demanded a more radical deployment of the same solution.
The Synapse has a very slim 25.4mm seatpost. Compliance is further improved by locating the clamp in the top-tube. pic: Marthein Smit
Moving the axle ‘backwards’ slackens its angle to the ground, Dodman explains. The advantage? Greater deflection when the fork is loaded. “Simply by moving the axle something like 7mm relative to the fork leg, you can get more comfort, without loss of performance,” he explains. The wheelbase of the Synapse is slightly longer than the EVO, he continues, and the head angle “a hair” more relaxed.
The dropout isn’t the only item of interest. The profile of the fork blades, another area of the Synapse with a helical design, changes on the journey from dropout to steerer. The different shapes serve different functions. The flattened blades are intended to deliver stiffness and so precision in cornering, and, further up, to resist flex when braking forces are applied. “Every part of the tube is specifically designed for a different function,” Dodman says. “The shape is functionally-driven, but still very beautiful.”
Dodman notes with some pride the enthusiasm of Cannondale Pro Cycling to race the Synapse; a situation he contrasts with a team being instructed to ride a given machine to satisfy the sponsor’s marketing goals.
“The EVO frame is the super lightweight race frame, and when it’s all about weight, they choose the EVO,” he says, “but when it comes to comfort and performance, over long rough rides, the Synapse is their choice.
“And it was their choice,” he continues, smiling, “not us saying, ‘you need to ride this.'”