Endurance bikes strike a balance between comfort and performance by utilizing less aggressive geometry and complaint setups to soak up harshness on the road. Cannondale’s popular Synapse series of bikes offer carbon fiber and aluminum options for new or experienced cyclists looking for comfort and speed. In this review, we’ll be specifically looking at the $5500 Cannondale Synapse Carbon 2 RLE which combines a full carbon frame with their innovative SmartSense system. As a mid-tier bike in the Synapse Carbon lineup, the Synapse Carbon 2 RLE comes equipped with the 12-speed Shimano Ultegra Di2 R8000 drivetrain with hydraulic disc brakes.

The bike also features the integrated SmartSense system which utilizes a central battery with internal cable routing to a Lezyne headlight, taillight and a Garmin Varia rear radar. Wide 700x30mm Vittoria tires combined with discreet flex zones in the carbon frame ensure a smooth and compliant ride. To simplify maintenance and upgrades, the Synapse Carbon features standard BSA threaded BB, flat mounted brakes and 12x142mm thru-axles. Cannondale also offers the Synapse Carbon in a number of variations from the $2600 Synapse Carbon 4 with Tiagra all the way up to the $9050 Synapse Carbon 1 RLE with Dura-Ace Di2.

The Cannondale Synapse Carbon 2 RLE combines a comfortable endurance frame with the seamless SmartSense light and radar system.

Retail Price$5500
RatingDesign: A
Components: A
Handling: A
Value: A
Weight (lb)19.8 (58cm)
Likes+ Full carbon frame
+ Comfortable endurance geometry and plush ride
+ Seamless radar and light system with SmartSense system
Dislikes– No upgrades for SmartSense system currently available
Where to Buy (US)Cannondale


The Cannondale Synapse Carbon 2 RLE combines classic endurance geometry with modern materials and sleek tube shaping. As a full carbon bike there are no seams in sight, instead you have sharp creases and detailing along the frame. To achieve a more upright position the headtube is quite tall with a styled “C” on the front. Cables for the front brakes are routed down into the front of the fork while the rear brake and SmartSense power cable tuck into the square shaped downtube. Cannondale currently offers this bike in two color options: Gray and the Cool Mint color shown in this review. Each Synapse Carbon models offers unique gloss color options as well as a beautiful color-shifting Purple Haze. Our Cool Mint bike received quite a few compliments as it combines an attractive glossy mint with metallic green highlights on the rear triangle and inner fork. Subtle graphic fades help blend the two colors together and give the bike a distinctive look.

Cannondale Synapse 2 RLE Carbon Endurance Road Bike Review - Side View
The Synapse has a classic endurance geometry with a tall headtube and offset seat stays for improved ride quality.

The bike has a sloped and tapered top tube with a slight bevel detailing along the inner triangle. For improved compliance the bike also features an offset rear triangle that allows Cannondale to optimize the geometry for each size. It’s a modern design feature found on other bikes such as the Decathlon Van Rysel EDR and gives the bike a more aero appearance. The rear stays are thin and flare outward to meet the rear hub and have a removable rear bridge. There is a fair amount of clearance around the stock 700×30 tires with an official tire clearance of 700×35. Even though the bike looks smooth and aerodynamic, Cannondale has incorporated four water bottle mounts including a top tube mount, which can also be utilized for top tube bike mounting, and an additional mount on the underside of the downtube. Extra features include hidden fender mounts on the fork and rear which allow the Synapse Carbon to be used in poor weather conditions or even setup for commuting.

Cannondale Synapse 2 RLE Carbon Endurance Road Bike Review - Headtube
Internal cable routing hides both the brake cables and the RLE’s headlight and taillight wiring through the frame.


As the mid-tier option in the Synapse Carbon lineup, the Synapse Carbon 2 RLE comes very well equipped with a full electronic Shimano Ultegra Di2 R8000 drivetrain. This includes flat mounted hydraulic disc brakes with 160mm rotors. The 12-speed setup is paired with a compact 50/34 Ultegra crank and 11-28 cassette which can easily handle steep climbs and fast sprints. As you’d expect, the Ultegra Di2 setup shifts smoothly and effortlessly under any condition. With a full hydraulic brake setup the bike also offers responsive and easy to modulate brakes to easily scrub speed off during fast descents or city riding.

Cannondale has also added a high quality finishing kit which includes a Fizik Argo saddle and Fulcrum Rapid Red wheelset. With its focus on comfort, the bike comes equipped with 700×30 Vittoria tires which feel fast and compliant. The only obvious in-house part is the Cannondale stem which pairs well with the bike with a matte black finish. Otherwise, the handlebars are an FSA drop bar setup which have a shallow bend that’s comfortable to use in the aero position. Even the Fabric branded bar tape feels soft and grippy with well placed Cannondale branded end tape. Aside from adding water bottle cages and some pedals., we suspect most people will enjoy riding the bike in its stock form.


One of the more controversial features of the Cannondale Synapse 2 RLE is the “RLE” part of the model name. This stands for “radar light equipped” and is part of Cannondale’s SmartSense system which is an integrated approach to lights and radars. The motivation for this system is to offer a seamless experience and eliminate redundant batteries and controls. With the RLE system you get the full experience with a Lezyne headlight, taillight and Garmin Varia rear radar. Cannondale also offers “LE” and “L” variations and sells all the components separately to allow people to upgrade. Note, you will need a SmartSense compatible frame to take full advantage of the setup and that individual components are quite expensive (i.e. the SmartSense battery without docking or wiring is $300).

The entire system is powered by a central removable battery mounted on the downtube just above the bottom bracket. While the power cables to the lights and radar are internally routed through the frame the battery itself is entirely exposed as it clips onto a mounting plate on the exterior of the downtube. Although most people would have preferred a more concealed battery, this design makes the battery easily accessible and doesn’t alter the geometry of the bike. The battery itself is 2665 mAh with a four LED battery status display and USB-C charging port. Not only does this central battery offer a more user-friendly experience, as you don’t have to charge each light and radar separately, but it can also be used as a power bank to charge other devices when you aren’t riding. One important note is that the electronic shifting components still use separate batteries, so you’ll still need to charge those separately.

Part of the magic of the SmartSense system is the Garmin wheel sensor on the front wheel which allows the entire system to automatically turn on or off when you start and stop riding. This means you can simply jump on the bike and have all the accessories auto-wake and ensure you’re visible and safe on the road. The headlight and taillight can be manually cycled through four different modes using a button on the rear of the headlight and automatically switch to a day and night mode based on the ambient light. Additionally, the headlight and taillight automatically react to cars detected by the radar and when it detects you slowing down. Unfortunately, all these smart features come at the cost of a proprietary setup which means you cannot swap out the lights or radars for other models. Cannondale also does not offer any larger battery sizes or light options, aside from StVZO regional variations, even after more than a year of being on the market which is a bit disappointing. With more aftermarket support or options we think the SmartSense system would appeal to more customers and riding styles. For example, we’d love to see an extended battery to minimize recharging or a high output headlight for night time riding.

Our bike came equipped with the non-StVZO variations of the Lezyne headlight and taillight which means the lights have flash modes and high output. The headlight has a reflector style beam cutoff, similar to the Trek Commuter Pro RT and Topeak WhiteLite BT, which eliminates any glare for oncoming traffic. The headlight is rated for 350 lumen while the taillight is 85 lumen which is on par with most daytime bright setups. Runtimes depend on the output mode and the active features with an official range from 4-20 hours with default settings. We achieved around 10 hours of runtime in real world riding as the brake sensor and radar activated warning modes can reduce overall runtimes. Having reviewed a lot of lights we’d call the stock setup good but not great, the taillight design lacks a focused LED while the headlight is quite large and lacks enough power for night time riding. While the setup isn’t our favorite, the Bontrager Flare RT and Magicshine Allty series offer better visibility, for daytime riding the setup offers good visibility and a seamless no-button experience.


To customize the SmartSense system or simply track or your ride, Cannondale also offers a full app. It’s clear Cannondale has invested time and money into the app as it’s highly polished and intuitive to use. The app has six main tabs that include: activity view, bike garage, active ride states, messages and a profile page. Once you connect to the app it shows you all the details for the bike’s stock components and even offers service reminders based on recorded ride time. A well designed ride page mimics a dedicated GPS display with a circular speed graph, ride stats and even a map view. The app can even connect to the rear radar and display radar information and trigger audible alerts to keep you aware of your surroundings.

The more exciting feature of the app is the ability to fully control and personalize the SmartSense system. You can change the output mode of the lights and adjust the setting such as: auto-adjust in low light, brake alert, low power mode, react to radar and even an auto proximity flash (i.e. the lights flash to greet you when you approach). All the settings are currently defaulted to be on from the factory except for the auto proximity flash. If you already have a dedicated GPS unit and are happy with the default settings, then you never need to download or bother with the app which is something we appreciate.


We put the Cannondale Synapse 2 RLE to the test by taking it on our short coastal morning rides and some challenging multi-hour climbs. In all situations, the bike feels comfortable and responsive. As an aggressive rider, we would have preferred a higher performance 700×28 tire setup but even on the stock Vittoria tires the bike is fun on road and can handle light gravel riding. The ride is comfortable and stable like the Trek Domane+ but with its 19.8lb weight it’s more fun to climb with. After a bit of tweaking to the saddle position, we found the bike to be compliant and easy to ride in both the aero and more relaxed upright positions. The high-quality components like the Fizik Argo saddle and soft Fabric bar tape provide comfortable contact points.

Cannondale Synapse 2 RLE Carbon Endurance Road Bike Review - Ultegra Drivetrain
The Synapse 2 features a full wireless Shimano Ultegra Di2 drivetrain with hydraulic disc brakes that shift quickly and confidently.

We found the compact crank and wide cassette gear ratios to be a great combination for steep climbs or sprinting on flats. The Ultegra Di2 has no trouble shifting down to the low gears and letting you spin up challenging climbs. It’s also easy to see the appeal of the thru-axle setup and hydraulic disc brakes as you get smooth and consistent modulation whether your braking at 40mph+ down steep descents or coming to a stop at an intersection. The bike feels similar to the Decathlon Van Rysel EDR we recently reviewed but features higher tier components and a corresponding higher price. We also quickly became accustomed to the SmartSense light and radar system which made it easy to check a single battery status and simply jump on the bike and ride. All the defaults worked well with the lights quickly switching to more powerful constant modes in tunnels and then switching back to daytime bright flash modes in brighter conditions.


Overall, we found the Cannondale Synapse 2 RLE to be a comfortable and well designed endurance bike. The combination of the full carbon frame and 700×30 tires provide a smooth and compliant ride that is happy to soak up the miles. With the Synapse 2 RLE version, we were impressed with the smooth and fast shifting the Shimano Ultegra Di2 drivetrain offered as well as the strong hydraulic disc brakes. Cannondale has done an excellent job putting the bike together as it uses high-quality components like a Fizik Argo saddle and a Fulcrum alloy wheelset. We particularly liked the Cool Mint color finish on the bike which combines a glossy mint color with a metallic green. The SmartSense system is also quite convenient as it integrates lights and radar onto the bike with a single central battery and button-less auto on and off capabilities thanks to a speed sensor.

Cannondale has designed the entire bike to be ready to ride right out of the box with a full featured companion app to track rides or personalize the light behavior. The main negative with the bike is that the SmartSense system lacks compatibility with third-party lights and has no upgrades currently. We’d really like to see some additional options such as larger batteries or a more compact daytime bright light setup. Otherwise, the bike itself is enjoyable to ride whether you’re doing a double-century or a high-intensity morning ride. While we enjoyed the Ultegra Di2 system we think the best value in the lineup would be the $3325 Carbon 3 L variation which gives you a mechanical Shimano 105 and the SmartSense light system sans the radar. That said, if you’re in the market for a fast and comfortable bike the Cannondale Synapse Carbon is one we’d recommend test riding.

Disclaimer: The product for this review was provided by Cannondale. The views expressed on this website are solely those of the authors and are here to help people make an informed choice before a purchase. The authors or the blog itself does not get any monetary compensation from the product manufacturer or third-party websites/vendor links that are posted here.

2 Replies to “The versatile and comfortable endurance bike”

    1. You can buy the cargo bike from Xtracycle directly – we aren’t suppliers or affiliated with the company.

Leave a Reply