Cannondale Synapse Hi-Mod Disc Dura-Ace Di2 review

Best-in-class endurance bike — if speed is of paramount importance

Road Bike
Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

The Cannondale Synapse Hi-Mod Disc Dura Ace Di2 was up for just about any adventure, including some early spring high country riding in Colorado.

What is it

The Synapse is Cannondale’s offering in the endurance race bike (not just endurance bike) segment. The Hi-Mod Disc Dura-Ace Di2 version, as you’ve likely guessed, is the no holds barred top shelf everything disc brake-equipped model that has an eye watering $10,000 price tag.

And while Synapse is not a new platform for Cannondale, this latest version makes some impressive leaps forward compared to its predecessor. Tops on that list is weight (or lack thereof). This latest Synapse Carbon frame is claimed to be 220 grams lighter than the outgoing version, and it has a total claimed frame weight of just 950 grams (size 56cm).

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

The non-driveside chainstay is larger than the driveside in order to deal with disc braking forces.

Cannondale also says stiffness has increased by 9.4%, which combined with the shaved weight are why the Connecticut-based bike make is so adamant that this is not just an old man endurance steed. Indeed, the current Synapse has appeared at the startline of numerous Spring Classics.

Other notable features include what’s become the industry standard of 12mm thru-axles and flat mount disc calipers, along with brake hoses that stealthily travel inside fork and frame for a smooth, clean look. There’s also a veritable two-faced rear triangle, where the non-driveside chainstay is nearly 20% larger than on the driveside. There’s similar asymmetry in the fork, which in both cases is done to resist flex during hard braking.

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

The integrated seatpost clamp means more exposed seatpost.

This Synapse also employs size-specific construction, where every frame size get its own carbon layup and tube dimensions. Additionally, Cannondale utilizes three different fork steerer and headtube diameters with three different fork offsets, again to ensure that every rider gets the same ride feel and handling, regardless of frame size, which include 48, 51, 54, 56, 58, and 61cm.

What the Synapse frame doesn’t have is any moving “suspension” parts (think Specialized Roubaix’s Future Shock or Trek Domane’s IsoSpeed Decoupler). Instead Cannondale’s endurance race steed relies on frame and seatpost deflection, the latter being a slim 25.4mm with a hidden seatclamp that increases the amount of post extended above the top tube.

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

Adjustment of seatpost height means playing around in that hole.

Seatpost deflection is coupled with the frame’s SAVE micro suspension (really just rear end give), which is claimed to deliver 3mm of bump absorbing movement. Ride smoothing is further enhanced by fast rolling Vittoria Corsa 700x28c tires, though adventurous types will be pleased to hear that there’s space for up to 32mm rubber if you’re so inclined.

All told there are 11 bikes in the Synapse Carbon family, plus four aluminum frame models. All but one come stock with disc brakes. Prices range from 10 large for the Dura-Ace Di2-spec’d bike that’s reviewed here, to a $1000 aluminum frame model with a Shimano Sora drivetrain. Our test bike in a size 61cm weighed a reasonably light (for a disc brake-equipped bike) 16.2 pounds.

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

Actual weight for this size 61cm was 16.2 pounds with tubes.

Pros
  • Smooth, but snappy ride
  • Reasonably light for disc brake-equipped bike
  • No moving frame parts
  • Clearance for up to 32mm tires
  • Discernable deflection from 25.4mm seatpost
  • Easy to access Di2 junction box on downtube
  • Different fork offsets and steerer diameters for various frame sizes
  • Stiff and responsive for an endurance bike
  • Reasonably aggressive geometry for an endurance bike
  • Dura-Ace Di2, enough said
  • Tubeless compatible 35mm deep carbon wheels
  • Plenty of gear range (50/34 chainrings, 11-30 cassette)
Cons
  • Integrated seatpost clamp tedious to adjust
  • Integrated seatpost susceptible to slippage
  • Seatpost shim can fall out of place
  • Lengthy headtube not so racy looking
  • Other endurance bikes absorb big bumps better
  • Not in love with two-tone color at this price point
  • Cornering response can be a little slow
  • $10,000 price tag
Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

Up, up and away on the Cannondale Synapse.

RoadBikeReview’s Take

Whether you should choose the Cannondale Synapse over another option among the current crop of racy endurance bikes really comes down to intended use and riding style. Having also spent time on most the mainstays in this category (Specialized Roubaix, Trek Domane, Giant Defy) I can honestly say they are all good bikes with strengths and weaknesses.

For my money, I’d place the Synapse near the top of heap if racing (or fast group riding) was a priority, and you weren’t planning to spend a ton of time venturing way off the beaten unpaved path. I write this because the Synapse is a fantastically stiff and efficient machine, but also not the most forgiving in this class, an honor I’d split between the Roubaix and Domane. Yes, the Synapse will take the sting out of choppy pavement, but potholes will remain potholes and rough road will still be rough.

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

For for those keeping score at home, that’s 23cm of headtube.

That’s not to say there’s no comfort on offer here. The Synapse’s length headtube (23cm on the size 61 frame) and rangy 1029mm wheelbase keep things stable and somewhat upright. And unlike the Roubaix or Domane, the frame has no moving “suspension” parts, which purists will certainly appreciate.

The Synapse — comparatively speaking — is also wonderfully light. The bike tested here registered 16.2 pounds on our garage scale, while a similarly high zoot spec’d Roubaix we have in for testing was a full 1.7 pounds heavier. That’s a significant difference when you’re shelling out 5 figures for two wheels.

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

ENVE carbon gets the nod for bar and stem duty.

I do, however, have to deduct points for the integrated seatpost clamp/seatpost, which I found incredibly tedious to adjust and prone to slippage if not slathered with excessive amounts of carbon paste. I get the rationale of maximizing exposed post for the sake of comfort, but wonder if the PITA factor is really worth the small gains in deflection.

Of course once you get your saddle height dialed this shouldn’t be a huge issue, which is why my bottom line on this bike is an enthusiastic thumbs skyward. The frame is light, stiff, and incredibly responsive. The bike is reasonably comfortable on all but the roughest roads. And handling is much closer to race bike snappy than endurance bike sluggish. And while that bong-sized headtube might scare some away, overall rider position is plenty aggressive for the general riding population who are seeking to go fast, but not have to be a yoga master to hang out in the drops.

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

Smooth rolling Vittoria Corsa tires are a nice touch.

Finally, props to Cannondale’s Hollowgram SL Carbon Disc wheels, which look great, come tubeless ready, have a category-appropriate 19mm internal rim width, and are 35mm deep with DT Swiss Aerolite bladed spokes, reminding its rider that this might be an endurance bike but its true talent is going fast.

Price: $10,000
Rating: 4 out of 5
More Info: www.cannondale.com

Cannondale Synapse Hi-Mod Disc Dura Ace Di2 Review

Full geo chart for the Cannondale Synapse Hi-Mod Disc Dura Ace Di2.

Photo Thumbnails (click to enlarge)
About the author: Jason Sumner

An avid cyclist, Jason Sumner has been writing about two-wheeled pursuits of all kinds since 1999. He’s covered the Tour de France, the Olympic Games, and dozens of other international cycling events. He also likes to throw himself into the fray, penning first-person accounts of cycling adventures all over the globe. Sumner, who joined the RoadBikeReview.com / Mtbr.com staff in 2013, has also done extensive gear testing and is the author of the cycling guide book "75 Classic Rides: Colorado." When not writing or riding, the native Coloradoan can be found enjoying time with his wife Lisa and daughter Cora.


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