Cannondale Synapse Hi-Mod Disc Dura-Ace Di2

First published 20 December 2017

Compared with the previous version, the new Cannondale Synapse is smoother, more comfortable, lighter and stiffer – and one of the best endurance bikes on the market right now.

• Pros: Lighter, better handling, stiffer and more comfortable than the previous bike
• Cons: Expensive in this build, not class-leading bump absorption

The Synapse traces its roots back to 2006, introduced at a time when demand was growing for bikes that offered more comfort than the race bikes they were loosely based on. For 2018 the Synapse has been taken back to the drawing board – and the results are very impressive.

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The new frame is not only lighter, helping to negate the disc brake weight penalty, it also has space for wider tyres and, recognising that it's a key bike for the UK market, mudguard eyelets.

Ride and handling

The Synapse has always offered lovely predictable handling together with impressive all-day comfort, but the new design is a noticeable improvement in every key aspect that defines how a bike performs. The changes that make it lighter, stiffer and more compliant help return the new Synapse to the front of the endurance bike pack.

The lighter frame certainly makes a noticeable difference to the overall weight; at 7.25kg (15.98lb) this 56cm bike is one of the lightest disc brake-equipped endurance bikes we've tested at road.cc, and it's knocking on the door of some race bikes. It's lighter, for example, than the Canyon Ultimate CF SLX Disc I tested back in March, though there are some spec differences that will account for some of that.

That helps it excel on the climbs, and on my local lumps and bumps the Synapse put in a stellar performance. Steep or gradual gradients, the Synapse makes great progress. And when you get out of the saddle to sprint the last 100 metres to the summit, the high level of stiffness from the fork through to the bottom bracket makes itself felt in how directly the bike responds, through the pedals and the handlebar.

On descents, boy is the Synapse an eager beaver. I had my first taste of the new Synapse's descending talents at the worldwide launch on the hilly roads around Lake Como in Italy earlier this year, and even on unfamiliar ground, blasting around blind bends, with erratic local drivers testing your commitment, it instilled great confidence. On more familiar descents around the Cotswolds, it's clear the longer wheelbase, bump-absorbing frame, grippy 28mm tyres and powerful Shimano Dura-Ace disc brakes combine to ensure descending is an area where the new bike shines.

It's not just on the climbs and descents that the Synapse is fast. On rolling, undulating roads the new bike can be pushed hard; the frame is super-responsive, with no undesirable flex robbing you of energy. It's a very efficient high-speed long-distance bike. Sure, the riding position is comfortable for riding all day, but shift down into the drops and it's as aggressive as most of us will want or need.

Noticeably stiffer

Cannondale has worked its engineering knowhow not only to create a frame that is lighter than the one it replaces but also one that is stiffer. It's noticeable too: the Synapse feels more immediate, more responsive than the previous bike. In fact, there's a hint of the SuperSix Evo about it.

That's one of the biggest highlights for me of the new Synapse: the way Cannondale has managed to move its endurance bike closer to a race bike in terms of handling and responsiveness while dialling in more comfort is very impressive. It's a great combination and one that will appeal to those who want their endurance bike served up with a large slice of speed and engagement.

It's definitely one of the racier endurance bikes, and draws parallels with the Canyon Endurace CF SLX and Trek Domane SLR.

While the comfort has been improved thanks to the wider tyres, new seatpost and refined frame design, it's not as bump-absorbingly smooth as the Specialized Roubaix. It's still a very smooth bike, comfortable on broken road surfaces, and it filters out bigger impacts nicely, but it's a firmer ride than the Roubaix.

If maximum isolation from the road is top of your list, you'll need to look elsewhere. If you want a simple and lightweight bike, the Synapse is the route to go.

Geometry

It's a very capable bike for all sorts of rides, with geometry that is more relaxed than a race bike but not as upright as some endurance bikes. I was as at home on fast-paced group rides as I was on long-distance solo romps, and never felt handicapped in any situation. Some of that could be down to refinements of the geometry, with the head angle a shade steeper and the wheelbase a touch shorter, injecting a bit more agility into the ride.

Geometry for the 56cm model on test here includes a 590mm stack and 386mm reach, 995mm wheelbase, 73-degree head angle and 173mm head tube. That creates a riding position that is higher and shorter than a race bike but still reasonably aggressive; it's likely to suit those who don't race and also those who might have recently hung up their race wheels but don't want to stop riding as fast as they can everywhere (eg, me).

Cannondale reckons the Synapse strikes the ideal balance between race bike aggressiveness and upright comfort. I'd agree with that. It's a balance that leans closer to race bikes than some, but the Synapse is still a very easy to ride bike, whether you have years of experience or are just starting out.

Cannondale says its goal for the new Synapse was to 'create a faster and higher performance bike for the rider who doesn't want to sacrifice speed for comfort', and in my opinion it's achieved that.

Frame design

The previous Synapse proved to be one of the class-leading bikes in the endurance and sportive category, developed for the cobbles of Paris-Roubaix yet right at home on an English country lane, providing comfort and an exciting ride. It's no wonder it was a hit with UK cyclists given the state of our roads.

First developed with rim brakes around a frame with some pretty interesting features, then given the option of disc brakes, the Synapse set the tone for the US company's endurance category. 'Combining a smooth ride with the stiffness and performance of a race bike, the revamped Cannondale Synapse impresses,' I said back in 2013. The same could be said now of the new bike.

The new Synapse has a visual similarity to its predecessor, but the disc brake-only frame is lighter, stiffer and more comfortable thanks to Cannondale's SAVE technology, where parts of the frame are designed to flex under load. It has wider tyre clearances, 12mm thru-axles and flat mount callipers, and now – finally (if hidden) – mudguard eyelets.

The headline-grabbing figure for the new bike is the 220g frame weight saving over the previous version, a size medium Hi-Mod frame coming it at 950g. The fork is 116g lighter than before at 367g.

Stiffness has been increased by 9.4% according to Cannondale, and narrows the gap between the Synapse and SuperSix Evo, resulting in that similarity in performance I mentioned earlier. Cannondale has taken a size-specific approach to the new Synapse, as it first did with the SuperSix Evo, to produce the same handling traits regardless of frame size. It optimises both the carbon layup and tube dimensions on each frame size, tailoring the stiffness for each.

It has also developed three new forks, with different offsets, to achieve this goal. Frame sizes 44cm and 48cm use a fork with a straight 1 1/8in steerer tube and a 60mm offset; sizes 51cm and 54cm use a tapered 1 1/4in steerer with 55mm offset; and 56, 58 and 61cm frames have a tapered 1 3/8in steerer tube, and 45mm offset.

Designed for disc brakes

Much of the weight and stiffness improvements have come about as a result of the asymmetric design of the new frame, intended to better manage the different loads from rider input and the disc brake forces.

The previous frame had a pretty curvy back end, but this new Synapse takes it to another level. In fact, the two halves of the rear triangle are totally different. The non-drive side chainstay is 18% larger in key areas than its opposite number, and the seat tube and down tube are asymmetrically offset around the 73mm-wide BB30a bottom bracket.

The fork also has a bigger left leg and directional carbon layup to resist flexing under heavy braking.

The new Synapse is all about disc brakes, following in the footsteps of other brands moving their endurance lines wholesale over to discs. They're hugely popular on non-race bikes ridden year-round in all sorts of conditions, and with the weight savings Cannondale has achieved with the new Synapse, there's no longer a significant penalty.

Cannondale told us committing to disc brakes enabled it to have more focus on the design, reducing weight and increasing stiffness in key areas. And, of course, disc brakes make it easier to increase tyre clearance: there's now space for 32mm measured tyres (the previous Synapse had clearance for 28mm), and all production bikes will come stock with 28mm tyres.

Cannondale has also improved the bike's versatility and added mudguard mounts, though you won't notice them unless you go looking for them. You can add a set of mudguards straight over the 28mm tyres. To fit the mudguards you simply need to add a removable rear brake bridge.

We might bang on about mudguards a lot here at road.cc, but when you've tried them it's hard to then face a wet wintry ride without them. A dry bum and legs make such a difference on a wet and cold ride, but a lot of the new breed of endurance bikes aren't catering for mudguard enthusiasts. So good work, Cannondale.

> Buyer's Guide: 10 of the best mudguard-compatible carbon fibre road bikes

The new bike has the now industry standard 12mm thru-axles and flat mount callipers, and the brake hoses are routed inside the frame and fork for clean lines. The gear cables or wires, depending on which groupset you opt for, are also internally routed, and Cannondale is using a single port in the down tube that, by changing the plastic plug, can accommodate any groupset. This Di2-equipped bike has the junction control box neatly in the down tube, so you can still easily access it when riding. It's a lot neater than being attached to the stem.

Comfort is key

Endurance bikes need to be many things to many people, but above all they need to be comfortable. Cannondale achieves that both through the geometry, which is more relaxed than a race bike, and through a combination of its SAVE technology – as I said above, a term it uses to describe parts of the frame designed to flex under load.

Cannondale hasn't resorted to any complicated moving parts, instead it relies on flex in the frame enhanced by tube shaping and carbon fibre layup to give the Synapse the ability to soak up bumps.

For the new Synapse the chainstays, seatstays and fork legs have been reshaped, providing more flex where it's needed. There's the same 25.4mm seatpost diameter, since adopted by the SuperSix Evo and Focus Paralane, but the new carbon fibre post has been shaped to improve the available deflection at the saddle. The seatclamp is hidden inside the top tube and increases the amount of seatpost extended outside of the frame.

You can detect the amount of fore-aft movement in the saddle easily when you ride the Synapse over a bumpy road; you can look down and see the saddle moving. It really does help to remove the harshness from riding along anything but perfectly smooth roads.

The saddle in question is a superbly comfortable Fabric Scoop Shallow Pro with carbon rails. Saddle shapes are very much personal things, but the Scoop is one that a lot of people seem to get on well with.

Bah, no bar

At the launch we rode Cannondale's new SAVE SystemBar handlebar, a two-piece carbon bar and stem that was designed to provide more deflection than a regular bar. The claim was that up to 6mm of deflection was possible, with testing showing upwards of 15mm.

Unfortunately, because of some production issues, 2018 bikes won't be fitted with this new bar and stem. Hopefully, we'll see it in 2019... That means current bikes will be fitted with substitutes, and on this high-end build it's an Enve Carbon Road Compact bar and stem, with a comfortable shape and easy-to-reach short drops. It's hard to find fault with an Enve setup, it's beautiful kit. A nice touch is the Garmin out-front mount attached to the stem faceplate.

Without testing the SystemBar and Enve setup alongside each other, it's impossible to say which provides the most deflection, but I will say I was impressed with the SystemBar at the launch, though I only had limited time with it and was riding unfamiliar roads.

What I can confidently say is that the front end of the Synapse is smooth and the bike has a very supple feel over bumpy roads. It's not soft and wallowy, and has a firmer ride than some endurance bikes, but critically it tames the biggest holes and cracks you might ride over. How much smoother it would be with the SystemBar is something I'll hopefully find out in the future.

Top spec

I was lucky to ride the range-topping Synapse, adorned with the latest Dura-Ace R9170 Di2 groupset and hydraulic disc brakes, including the funky new disc rotors that are designed to reduce heat buildup for more dependable braking.

This bike costs £7,799, and there's no denying it, that's a lot of cash. The carbon Synapse range starts at £1,399 with Tiagra, though that cheapest model and the £1,599 bike above it both use the previous frameset. Step up to £2,199 and you'll find the cheapest model with the new Synapse frame, and there are another seven models before you get to the bike tested here.

Unfortunately, the test bike had the older R785 brake levers and not the newer R9170 hoods, but bikes in the shops will have the newer levers. These are significantly more compact and nicer to use than Shimano's first road hydraulic lever, which now looks a bit clunky.

Cannondale substitutes the Shimano crankset for its own Hollowgram SiSL2 design, which certainly looks distinctive and is one of the lightest cranksets on the market. It's an opinion divider for sure, based on the road.cc forum comments, but on the bike there's little to tell it apart from Shimano's latest crankset, so performance is more than acceptable. The gear range – 50/34t chainset and 11-30t cassette – is suitably capable for high-speed shenanigans and grunting steep climbs.

Increasingly in recent years, bike brands have been designing, producing and speccing their own wheels. Trek, Giant, Specialized... they're all at it. Cannondale's Hollowgram SL Carbon Disc wheels are a tubeless-ready design thanks to a collaboration with Stan's NoTubes, so shedding the inner tubes should be an easy task.

The 35mm-deep carbon rims have a 19mm internal width and are laced via DT Aerolite bladed spokes (24 front, 28 rear) to Hollowgram hub shells with DT Swiss internals, and Centerlock disc mounting hardware. Claimed weight for the wheelset is 1,417g.

I couldn't find anything to fault with the wheels. They're comfortable, stiff enough and provide good aerodynamic performance, with the shallow depth stable in windy conditions. On the miles logged so far, they've proven reliable and dependable. 

Vittoria tyres aren't a common sight on production bikes, but Cannondale told us at the launch of the new Synapse that it arrived at these tyres through extensive testing, finding the ride characteristics met its requirements for this bike.

Inflated to about 70psi, the tyres are supple and cushioning on the road, yet with good rolling resistance on the evidence of my informal roll-down test. Durability seems good too, with no flats during the test period and no distress to the rubber from sharp flints and stones.

Overall

The new Synapse offers a smooth, comfortable, responsive and fun ride. It's equally at home on very long distance rides where comfort and low weight are a priority (for the climbs) and short blasts where speed matters.

It's a case of evolution rather than revolution. Cannondale has kept the solid foundations of the previous Synapse and improved it in a number of ways, resulting in a bike that is snappier, faster, more fun, smoother and more composed on the rough, with space for wider tyres and the option, at last, to fit mudguards.

The lighter frame also reduces the previous weight penalty associated with disc brakes, meaning you can have better braking with fewer drawbacks.

Verdict

Fast, smooth and fun, the new Synapse is an exceedingly good endurance bike