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Cannondale Synapse Carbon 4 review

Stripped-down long-distance machine

Our rating 
3.5 out of 5 star rating 3.5
GBP £2,400.00 RRP | USD $2,425.00 | AUD $4,199.00
Pack shot of the Cannondale Synapse Carbon 4 road bike

Our review

The new Synapse is a real joy to ride – but in this guise it lacks value against its competitors
Pros: Comfort and handling are class-leading
Cons: Not great value for money
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The latest Cannondale Synapse has, for the first time, stepped away from the racing associations that saw previous versions being ridden to victory at Gent-Wevelgem.

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Instead, the new Synapse’s design is more about meeting real-world riders’ needs and providing practical usability.

On higher-spec models, such as our endurance Bike of the Year, the Synapse Carbon LTD RLE, that’s more obvious: it even comes with an integrated lighting system.

Our test bike has no electronics, but with the same high-quality frame as those top-tier models, you could upgrade later.

Cannondale Synapse Carbon 4 geometry

Rather than press-fit, the Synapse Carbon 4 has a BSA bottom bracket.
Steve Sayers / Our Media

The geometry is very similar to the previous, much-loved Synapse. Compared to the geometry on Cannondale’s SuperSix EVO race bike, it’s around 15mm taller at the front and 8mm shorter.

It’s a subtle difference, but it means while you can still get properly speedy in the drops, it’s just that bit easier to live with.

The wheelbase has been increased to allow tyres up to 35mm wide with 6mm of clearance, allowing full mudguards with the standard 30c tyres.

A shorter 56mm trail figure helps retain the bike’s agility, and it’s the combination of that agility and comfort that makes the Synapse stand out.

Size (cm)48 51 54565861
Seat angle (degrees)737373737373
Head angle (degrees)71.371.473.173.273.373.4
Chainstay (mm)415415415415415415
Seat tube (mm)407443480520550590
Top tube horizontal (mm)533544555567579598
Top tube actual (mm)510521533547560579
Head tube (mm)10913043164187218
Fork offset (mm)555545454545
Trail (mm)595858575656
Bottom bracket drop (mm)757573737070
Bottom bracket height (mm)270270272272275275
Wheelbase (mm)9911,0029879981,0111,028
Standover (mm)712742773877833868
Stack (mm)530550570590610640
Reach (mm)371376381387393402

Cannondale Synapse Carbon 4 frame details

The rear triangle and seatpost offer a little flex.
Steve Sayers / Our Media

That Synapse Carbon 4’s frame really is the star of the show. In addition to that well considered geometry, it has an extra set of bosses on the top tube, there’s a battery port on the down tube and smart-trainer compatible bolts for the rear thru-axle.

At 1,015g, the frame still comes out 20g lighter than previous-generation bikes.

It’s made using Cannondale’s ‘proportional response construction’. This means each frame size has its own construction, so the largest 61cm frame size and the smallest 48cm share exactly the same ride quality.

Cannondale Synapse Carbon 4 ride impressions

Tiagra sits two steps below Ultegra.
Steve Sayers / Our Media

The ride quality is, quite simply, brilliant, rolling smoothly and absorbing vibrations seemingly at will. The ride position is exactly what I want from a quick road bike – it’s sporty without being stretched.

The handling feels much more nimble than my own 2014 Synapse – and it’s wonderful. The Synapse also shares much of the 2022 SuperSix EVO’s fast yet balanced handling.

The bigger tyres bring bags of grip, making this Synapse a great descender. Allied to the smoothness of the ride and fast handling, it results in the Synapse feeling more accomplished than many of its rivals.

Sadly, however, that’s where the praise pauses. As wonderful as the core of the Synapse is, elsewhere the Carbon 4 can’t even get close to the value of the competition it’s up against.

It’s not that Shimano’s 10-speed Tiagra is poor. In fact, it’s a remarkably slick-shifting setup and the 50/34 chainset and 11-34 cassette is a perfect pairing for the Synapse’s mile-munching intentions.

Similarly, the hydraulic Tiagra brakes are full of feel and plenty of power, even if they do offer the occasional noisy protest when they heat up.

It’s just that Tiagra is out of place on a £2,400 bike – especially when the Cube Attain GTC SL has Ultegra, which is two steps above Tiagra, and the Giant Defy Advanced 0 has SRAM’s Rival wireless electronic AXS.

The Cannondale-branded alloy components are all good, serviceable stuff. I like the bar shape and the high-quality, comfortable bar tape. Fizik’s Aliante saddle is also high on comfort.

The Vittoria Zaffiro Pros may not be the fastest road bike tyres, but they add plushness and all-weather grip.

The competent alloy wheels use Formula’s dependable hubs and the 21mm internal-width rim shapes the tyre well. And while not light, they are tough.

I appreciate the inclusion of the Garmin-collaboration wheel sensor, which you can also use in combination with Cannondale’s app to give you GPS levels of ride recording for free.

Cannondale Synapse Carbon 4 bottom line

Sloping top tube? Dropped seatstays? Yep.
Steve Sayers / Our Media

Overall, as much as the Synapse Carbon 4 perfectly balances handling with comfort, and doesn’t hold back on the fun, I couldn’t recommend it at this price.

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The impressive ride deserves your attention, but I’d strongly suggest saving for the £3,200 Carbon 3 L or blowing your budget on the brilliant – but expensive at £6,500 – LTD RLE.

How we tested

Endurance road bikes, at first glance, look much like the bikes you’ll see professional cyclists riding, but look more closely and you’ll see there are some subtle but significant differences, which make them more suitable for the likes of you and I.

An endurance bike is made for day-long comfort, for example, with a more upright geometry to suit. They will often be designed with versatility in mind, too, with clearance for wider tyres and mudguard mounts for winter riding.

In this test of three of the best endurance road bikes around £3,000, each machine was set up and checked over by our workshop manager, Will Poole, before going to our senior road technical editor, Warren Rossiter.

Warren tested all three on his go-to roads on Salisbury Plain, including a high-tempo, two-and-a-half-hour ride to dial each bike in, before multiple outings on an 82-mile (132km) loop.

For good measure, and to see just how versatile the latest gravel bikes are, Warren also took in some of Salisbury Plain’s wide gravel roads.

On test

  • Cannondale Synapse Carbon 4 review
  • Cube Attain GTC SL
  • Giant Defy Advanced 0

Product Specifications


Price br_price, 5, 3, Price, AUD $4199.00GBP £2400.00USD $2425.00
Weight br_weight, 5, 6, Weight, 9.46kg (58cm), Array, kg
Brand br_brand, 5, 10, Brand, Cannondale


Available sizes br_availableSizes, 11, 0, Available sizes, 48, 51, 54, 56, 58, 61cm
Bottom bracket br_bottomBracket, 11, 0, Bottom bracket, Shimano BSA
Brakes br_brakes, 11, 0, Brakes, Shimano Tiagra hydraulic disc, 160mm RT64 rotors
Cassette br_cassette, 11, 0, Cassette, Shimano Tiagra 10-speed 11-34
Chain br_chain, 11, 0, Chain, Shimano Tiagra
Cranks br_cranks, 11, 0, Cranks, Shimano Tiagra 50/34
Fork br_fork, 11, 0, Fork, Full carbon
Frame br_frame, 11, 0, Frame, Carbon, SmartSense enabled
Front derailleur br_frontDerailleur, 11, 0, Front derailleur, Shimano Tiagra
Grips/Tape br_gripsTape, 11, 0, Grips/Tape, Fabric Knurl Bar Tape
Handlebar br_handlebar, 11, 0, Handlebar, Cannondale Three 42cm
Rear derailleur br_rearDerailleur, 11, 0, Rear derailleur, Shimano Tiagra
Saddle br_saddle, 11, 0, Saddle, Fizik Aliante Delta S-Alloy rails
Seatpost br_seatpost, 11, 0, Seatpost, Cannondale Four alloy
Shifter br_shifter, 11, 0, Shifter, Shimano Tiagra
Stem br_stem, 11, 0, Stem, Cannondale Four alloy 100mm
Tyres br_tyres, 11, 0, Tyres, Vittoria Zaffiro Pro Reflective 700x30c
Wheels br_wheels, 11, 0, Wheels, RD3.1 28h, 21mm inner width