Cannondale Synapse Carbon 2 SmartSense review: the new gold standard for endurance bikes

The Cannondale Synapse Carbon 2 SmartSense delivers everything I want from an endurance bike in 2025.

The Synapse Carbon 2 comes with all the characteristics that made the Lab71 outstanding, for £5,750 less – the Snyapse Carbon 2 has an RRP of £7,250 / $8,199 / €7,899.

While the range-topping Lab 71 Synapse blew me away with its overall performance, the astronomical price tag put it in pipe-dream territory for the vast majority of riders. That’s why I couldn’t wait to get my hands on one of the other options at a more achievable price.

The Synapse Carbon 2 is exactly what I want from a modern endurance bike; it's smooth and comfortable while still being an exciting and fun ride.

Combine that with the clever safety features of SmartSense and the practicalities of the design, and it makes for one of the most complete road bikes for year-round riding on sale today.

Cannondale Synapse Carbon 2 SmartSense frameset

The Cannondale Synapse Carbon 2 SmartSense features Cannondale’s second-tier carbon layup, but the design is the same as the Hi-Mod carbon bikes above it, weighing 150g more (1,150g claimed for a size 56cm).

It’s worth noting that the Synapse Lab71 features Hi-Mod grade carbon too, rather than the ‘Series 0’ carbon found in the SuperSix Evo Lab71. 

In any case, the same aerodynamic profiles, with compliance built into the back end thanks to slim tubes, and mudguard/fender eyelets, bento box mounts, and down tube storage, are all included. 

There’s also clearance for 42mm-wide tyres, which makes the Synapse a standard-setter.

The frameset also integrates the safety-enhancing SmartSense system, with a single central battery that powers the SmartSense lights and radar.

You can see elements of the Synapse design in both the SuperX gravel race bike and the SuperSix Evo that Ben Healy rode to two days in the yellow jersey at this year’s Tour de France.

The frameset features the same Delta steerer as the SuperSix Evo, which enables the brake hoses to run internally while still using a standard 1-1/8in x 1-1/2in headset. 

Like all of Cannondale’s road offerings now, it also features a threaded BSA bottom bracket. Gone is the Cannondale-designed BB30 press-fit design, relegated to history alongside other Cannondale innovations such as Ai offset wheels, HeadShok and Hollowgram Si cranksets.

The rear dropout is now SRAM UDH, which makes gear hanger replacement simple (because it’s a universal design). It also allows for direct-mount rear derailleurs to be used – something seen on the latest SRAM XPLR derailleurs.

The front end is reminiscent of the SuperSix, with the integration of the fork crown into the head tube, itself a blend of a truncated aerofoil and an hourglass front profile. 

The down tube follows a similar approach to aero optimisation, while the top tube flattens towards the seat cluster to aid compliance. The seat tube starts as a truncated aerofoil, then flattens in its lower third and tapers with a curve to aid both tyre/fender clearance and compliance. 

This is further aided by the flattened and arched dropped seatstays, and the chainstays follow the familiar SAVE profile that’s been a staple on the Synapse since the 2014 model.

Cannondale claims the latest Synapse is 20% more compliant than the previous model, while increasing both head tube and bottom bracket stiffness.

The integration of SmartSense is much cleaner than before. Where the previous bike had a recess in the down tube and an external battery, the latest design hides the battery inside a well-proportioned down tube storage port. 

The battery powers the front and rear light radar combo and the two derailleurs of a SRAM AXS drivetrain (it won’t power Shimano derailleurs, though, arguably informing Cannondale’s decision to equip SmartSense-fitted bikes with SRAM groupsets only). 

The battery can either be removed to charge or charged in place via a USB-C port just above the storage hatch. In a pinch, this can also be used as a power bank.

Cannondale Synapse Carbon 2 SmartSense geometry

Cannondale hit the endurance geometry sweet spot way back in 2014. That Synapse had endurance-focused geometry when it came to ride position, but steering geometry that was closer to a fast-handling race bike.

It certainly worked back then, with that model taking our Bike of the Year title. Here, it's a case of if it isn’t broke, don’t fix it. The changes have more to do with the changes in tech over the intervening years. 

The head angle of 71.5 degrees is 1.5 degrees more relaxed than previously. This, however, is offset by using a longer fork with a tweak to its offset. So, with the 32mm tyres that come fitted as standard, it makes for a 61mm trail figure, 2mm up from the previous generation's 59mm, and only 3mm longer than the SuperSix Evo, a bike renowned for its quick, reactive steering. 

The new fork has 42mm of tyre clearance on paper, although in the flesh, 42mm feels conservative. Anyway, it's amongst the largest tyre clearances we’ve seen to date on an endurance bike. More tyre clearance will inevitably add to the wheelbase, seen here with the extension on the chainstays to 43cm from 41.5cm. The wheelbase was 105.8cm on my 58cm test bike.

Cannondale Synapse Carbon 2 SmartSense specification

The Synapse Carbon 2 SmartSense uses SRAM’s Force AXS groupset, here with the 46/33-tooth chainring combination and a 12-speed 10-36t cassette. It’s an interesting choice, wider than SRAM's recommended ratios (46/33t, 10-33t) but still giving a taller gear than a standard 50x11t, and an inch smaller at the other end than a 34x36t commonly found on endurance bikes.

The Force AXS drivetrain relies on the SmartSense central battery for its power, where Cannondale has cleverly employed SRAM’s EP-EAC extension cord, used on ebikes to power AXS derailleurs. 

This means the derailleurs look much svelter without the AXS batteries, but in a pinch, you can install one to help get you home, albeit Cannondale says the battery keeps a small reserve back for the derailleurs.

The SmartSense battery also powers the combined lighting and traffic-sensing radar system of the same name. It, along with the wheel speed sensor and, of course, SRAM’s AXS, combine to make the Synapse Carbon 2 a data-rich experience and one that boosts your safety on every ride.

You get the same lights as on all other SmartSense-equipped bikes – an 800-lumen (or 400 in STVZO-compliant countries) Lightskin front light, and Garmin's Varia eRTL 615 radar light.

The central battery tucks away low down in the down tube and features a light to illuminate the compartment above it, in which lives a storage bag. 

The bike rolls on Reserve’s 42/49 Turbulent aero carbon rims, which are the same rims as those found on the range-topping Lab71. Here, however, they are paired with DT Swiss 370 hubs rather than the featherweight 180s on the premium model.

It’s still a £1,599 wheelset at retail, with a progressive 25.4mm inner width at the front and a 24.8mm width at the rear. That’s also reflected in the outer width – 34.4mm front and 32.1mm at the rear. 

These come with a claimed weight of 1,450g and are wrapped with Vittoria’s Rubino (tube type) tyres, with tanwalls in a broad 32mm width.

Completing the build is Cannondale’s own Conceal C1 stem, combined with a Vision Trimax alloy bar up front. The bar measures up at 409.5mm at the hoods, with a subtle 4-degree outsweep that pushes the drops out to 420mm. 

It may ‘only’ be an alloy bar, but I found it just as comfortable as many carbon bars. The flattened and shaped aero tops are great to hold and the semi-compact drop flares enable my wrists to clear when sprinting out of the saddle.

At the back, the bike sports Cannondale’s slender 20mm-offset proprietary carbon seatpost, first seen on the SuperSix Evo. Zero-setback models are specced on smaller sizes, but you can’t swap them free of charge at the point of purchase. 

This is topped with Fizik’s Vento saddle in R5 (chromoly-railed) spec.

Cannondale Synapse Carbon 2 SmartSense ride impressions

The SmartSense system is worth every penny. From initial setup by registering the bike with the Cannondale app (which doubles as an ownership ID and is useful for warranty issues should anything happen down the line) to setting up your preferences – light modes, radar settings and a full status on your phone – it’s tech that makes it feel the endurance bike has evolved. 

Add to that the SRAM AXS ecosystem and the Synapse becomes a data-rich experience before you’ve turned a pedal.

When I turned the pedals, I found it easy to forget I was on an endurance bike. I’m familiar with the new frame design, having spent a lot of time on the latest Lab71 model and owning the previous high-watermark 2014 Synapse. That was the first one to combine the smoothness of an endurance bike with the lively ride of a race bike.

The 2025 iteration gets this combination in spades. Its quick-yet-confident steering blends wonderfully with a frameset that isolates you from the worst energy-ebbing vibrations, while still giving you enough feedback to read the road surface and get an idea of grip when heading into a corner at pace.

The Synapse is oblivious to road surfaces that see my own SuperSix Evo knocked off-line. Some of that road-smoothing ability is down to the tyres, which come up at a fraction over 35mm on the wide Reserve rims. 

The lightly patterned Rubino tread is a good all-surface option. It may not have the low rolling resistance performance of Vittoria’s Corsa Pro, but I never felt it was an overly sluggish-responding tyre; the latest Rubino here is streets ahead of the previous version.

Of course, it being a clincher tyre, rather than tubeless, may put some off. That said, with modern lightweight inner tubes, at least the clincher is still a viable choice in performance terms.

The drivetrain and braking are impeccable; my personal bike runs SRAM Red AXS, and this new Force AXS, which takes its design cues from Red, is easily its equal (save for the weight). 

The Reserve wheels are stiff, responsive and have a modern aero shape; they may only have DT’s more modest 370 hubs at their heart, but those are tough, reliable hubs that will last the test of time.

The handling is confidence-inspiring and the on-road comfort is among the finest I’ve ever experienced.

Cannondale Synapse Carbon 2 SmartSense bottom line

The Lab71 incarnation of the Synapse blew me away; it was everything I could want from an endurance bike and more. The Synapse Carbon 2 comes very close to the Lab71 in pure enjoyment terms. 

Is it perfect? Not quite – at this price, I’d like to have seen a carbon bar, but that’s almost vanity, because the Vision Trimax bar is very good.

Would an alloy bar stop me from recommending the Synapse Carbon 2 to anyone looking for an endurance bike? Not at all. If you are looking for a road bike that’ll give you everything you’d want, then look no further.

Arguably more importantly, the Synapse represents the new template for a non-racing road bike. It has handling that’s swift and stable, and gives confidence in spades. It's compliant but doesn’t lose the excitement that comes from a stiff bike, plus it features the best application of the SmartSense system to date.

The Synapse Carbon 2 SmartSense is an exciting ride and a sensible choice; it’s a rare thing to draw both those conclusions about a single bike.