The Synapse Carbon 4 is an exceptional balance of bike for your money. Equipped with DT Swiss rims laced onto Shimano hubs and shod with Vittoria tyres, plus a full suite of Shimano 105 Di2 12 speed components, the Synapse 4 offers precise shifting and confident control. A Vision Trimax aero bar and Cannondale Conceal stem deliver comfort, aero and adjustability to round out the bike. Available in Metallic Red or Chalk White.
At the advent of a revolution in the road cycling market some 20 years ago - the move to mass adoption - the original Synapse cut a new path. By marrying race-level performance and weight with real-rider geometry, comfort and handling, the Cannondale Synapse established the benchmark for what would become “Endurance road”. Indeed - it was the first bike to ever win back-to-back Bike Of The Year awards, such was its relevance.
Two decades and six generations of Synapse later and it continues to lead the bunch in defining what the future of core road bikes will look like. It continues to magically blend legendary comfort with the thrill and excitement of a road race bike.
Let’s not sugar coat it too much though. There have been wobbles. The first generation SmartSense bikes were not met well by dealers or riders alike and despite claims of simplicity, these were overshadowed by clunky application of smart features (often the way when you hop on a wagon early). It almost destroyed the platform in the UK, pigeonholing riders into a seriously tight niche that made huge assumptions about the type of rider that rode them. This was a real shame since the underlying geometry and ride has always delivered beyond other endurance platforms.
The Synapse Geometry has been a defining selling point - both generally and even within the Endurance road category - being as it is, a beautiful balance of race vs comfort. For many, the reactiveness of a bike is what keeps it fun and engaging, and while other platforms in the genre often lacked spark, the Synapse has always delivered. In fact, unless you’re a WorldTour pro or racer, the Synapse is the perfect road bike for any job. Factor in a raft of new aerodynamic developments that put some race bikes to shame, and the new Synapse delivers WorldTour-level aerodynamics and stiffness-to-weight, with top-tier tyre clearance, compliance, and smart features for a platform that will exceed expectations. The new Synapse is built for speed - but over the long haul, with the comfort to keep you smiling 6 hours in.
In fact, Cannondale have refined their carbon layup with advancements in materials and approach, making the new Synapse 20% more compliant than its already butter-smooth predecessor. That’s a BIG number and ensures you feel more comfortable even on the roughest roads.
Fit - as touched on - is pivotal, and Cannondale’s Proportional Response Construction ensures that you experience the benefits of the Synapse design no matter if you need to ride a 48cm or a 61. Through carbon layup and geometry, everything on the Synapse has been tuned and tested by frame size
Each model in the range features Cannondale’s new StashPort downtube storage system. As one who has experienced a similar feature on the Enve Fray, I can attest to the joy of emptying your pockets and lowering your centre of gravity with convenient storage. There when you need it and out of sight when you don’t, it is designed to work seamlessly with the supplied StashBag to keeps your ride essentials secure. Additional, hidden top tube bag mounts, discreet mudguard mounts, and room for 42mm tyres, the new Synapse is built to go long and go hard, no matter what the day brings.
The latest generation Synapse gives you something that the previous iteration failed to deliver at launch. Choice. The new Synapse gives riders options of SmartSense equipped models, or just the bikes - so you can evolve them as you need.
SmartSense to the initiated - may cause flashbacks (as it did when they were first waved in front of me this time around) - but rest assured, there should be no lingering PTSD. Cannondale have paid close attention to feedback from dealers and riders and the second generation SmartSense - available on the LAB71, and 2 additional models as standard - has been seriously refined to be beneficial rather than a cheap, clunky non-option!
More discreet, more integrated, and more powerful than ever, SmartSense is now an intelligent, connected system of lights, radar, sensors, and the Cannondale app. Together they bring peace of mind to every ride. Running from a single concealed battery, the rear-facing Garmin radar keeps you switched on to approaching traffic, while intelligent headlights and taillights adapt blink patterns and/or brightness to let other road users know you’re there. It will even power your SRAM AXS shifting - with just 5% of the battery’s charge delivering a full battery charge of a single AXS battery. With just one long-lasting battery to charge, it’s easier than ever to get out and ride
Much has changed - like the UDH compatibility, ensuring upgrade paths beyond the norm - but some key developments ensure simplicity remains to the fore. The BSA threaded bottom bracket simplifies the crank interface and a new Delta Steerer makes for less fussy internal routing of hoses at the front end and keeps the aero profile on point.
Essentially the Synapse is back to its former genre-defining glory, with the option to take advantage of SmartSense for a fully connected and simplified riding experience. Racy feel with comfort for days means you can take on anything from Crits to stage races or epic multi-day expeditions in the mountains - all while ensuring you are ready to go again tomorrow.
Key Features:
- Road Endurance
- Tyre Clearance up to [F] 48mm [R] 42mm
- UDH Compatible
- StashPort
- Concealed Top Tube Bag Mounts
Synapse : Need to Know
Q – What are the main differences and improvements from the previous Synapse to the new Synapse?
A – In a word - everything. It is more comfortable, more aerodynamically efficient, and more sleekly integrated. It has room for way bigger tyres, is UDH compatible, and now has the convenient StashPort in the downtube. Select models come with the wildly improved, smaller-lighter-more powerful SmartSense Gen 2 system. And with the new Hi-MOD frame versions, Cannondale managed to add all of that performance and reduce the frame weight. All while retaining that awesome Synapse ride feel where high performance meets high comfort.
Q – What is the largest tyre I can run on the new Synapse?
A – Synapse models are compatible with a maximum measured tyre width up to 42mm for the frame and 48mm for the fork provided that at least 4mm of clearance exists between the tyre and the frame, fork, mudguard and its attachment hardware, or any drivetrain components when the wheel is rotated to any position. Verify that tyre width and frame clearance is measured with the tyre inflated to the lower of the maximum inflation values recommended on the rim and on the tyre.
Q - What is the maximum rotor dimension?
A - Rear: min. 140mm, max. 160mm / Front: min. 160mm, max. 180mm
Q – What kind of axles are compatible with Synapse?
A – Rear: Syntace TA 142x12mm, 163mm Overall Length / Front: Syntace TA 100x12mm, 125mm Overall Length
Q – Is Synapse approved by the UCI for racing?
A – Yes, it is.
Q – What are the dimensions for the bottom bracket and headset?
A – Bottom Bracket 68mm BSA / Headset: Integrated IS245-COA, Top: 1.125”, Bottom: 1.5”
Q – What is the difference between the carbon layup used with the LAB71 version and the rest of line in terms of weight, stiffness and material?
A - To begin with, a painted LAB71 SuperX frame in size 56 weighs under 1000 grams. When comparing the materials used in the limited-edition LAB71 models to the rest of the Synapse line-up, the LAB71 complete bike and frameset feature a higher proportion of high-tensile modulus fibres. These fibres allow Cannondale to use fewer overall fibres, as the desired stiffness is achieved more quickly. Additionally, Cannondale use higher tensile strength fibres as well, enabling them to use less material while still achieving the necessary strength. The result is a weight saving of over 100g for the LAB71 Synapse and Synapse 1 model compared to the frames used for the rest of the 2025 Synapse range, without compromising stiffness or strength. And, of course, both frames carry a limited lifetime guarantee.
Q - What is the maximum system weight?
A – The total weight limit for the Synapse is 150kg/330lbs, which includes the combined weight of the rider, bike, and all equipment.
Q – Can I change between 1x and 2x cranksets?
A - Yes, both options are available. If you switch from 2x to 1x, you can remove the front derailleur mount for a cleaner look.
Q – What is the cable routing compatibility on Synapse?
A – The Synapse ́s Delta Steerer system is engineered to integrate effortlessly with the SystemBar R-One and Conceal stem, enabling cables to route cleanly from the handlebar into the frame, whether you’re using electronic (wired or wireless) or mechanical shifting. To simplify things for riders with multiple Cannondales, the Synapse uses the same dust cover and headset spacers as the SuperSix EVO, making it easy to find small parts. And should you ever want to run something other than the SystemBar or Conceal stem, Delta Steerer is compatible with most standard 1-1/8” stems – you just need a different dust-cover, spacers, and top cap.
Q – What seatpost options are there for Synapse?
A – Synapse-compatible seatposts come with either 15mm and 0mm offsets. To keep it simple, it's the same post as those found on SuperSix EVO Generation 3, CAAD13, and the new SuperX. Frame sizes 44-48cm come with 0mm offset seatposts while sizes 51-61 are shipped with the 15mm offset version.
Q – Are there any mounting points for mudguards on Synapse?
A – Yes, Synapse is built to make all-day and all-weather riding a breeze. For frame sizes 54cm-61cm, the rear guard attaches to a removable seat stay mudguard bridge, while sizes 44cm, 48cm, and 51cm use a rivet nut mount on the rear of the seat tube, which may require modifications to the guard for proper installation. On size 54 frames, you may also need to adjust the L-shaped bracket to fit the removable seat stay bridge. Rear mounting points are located at the removable seat stay bridge for 54cm-61cm frames, at the rivet nut on the rear seat tube for 44cm, 48cm and 51cm frames, and at the dropout. The front mudguard mounts at the rear of the fork crown and inside the fork blades. Depending on the guard design, you may need to bend or trim the mounting struts for a secure fit.
Q – Is the StashBag, the internal storage bag, included with every model in the Synapse range?
A – Yes, the StashBag comes with every model, including the ones equipped with SmartSense.
SMARTSENSE
Q - What is SmartSense?
A - SmartSense is a system of parts which can all communicate with each other as well as to a smartphone and share a single battery. By sharing the same battery and communication language, SmartSense components can be smaller, more integrated, more convenient, and can do more together than what is possible with individual aftermarket pieces.
Q - Is SmartSense exclusive to Cannondale?
A - Yes, SmartSense is an exclusive Cannondale technology.
Q - What components make up SmartSense?
A – Differentiating between base system components and additional components:
SmartSense™ Base System Components:
- SmartSense Gen. 2 Battery: Just one battery to charge it all. Now packing a huge 43.2Wh, this is the power for the whole SmartSense system. As a side note, you can use it to charge your phone at the coffee shop by using the USB-C port on the top or as a flashlight if you ever need one.
- Garmin Varia eRTL Radar/Taillight– All Gen. 2 SmartSense bikes come with radar, electronic shifting, a headlight and taillight. The eRTL includes the radar and taillight
and is also the link between your Cannondale app and the rest of the system.
- Cannondale Wheel sensor – Tells the SmartSense system when you are riding and automatically records your riding activity for you.
- SmartSense LightSkin Headlight – The smallest and brightest headlight possible. Integrating LightSkin’s U1E headlight into the system. With an 800 lumen output, this is bright enough to ride all day and into the night.
- Sram AXS Extension Cord – Powers AXS derailleurs from the SmartSense battery
- Cannondale App – While the SmartSense system is fully functional without it, with the app you can customise your light and display settings.
Additional Components:
- Garmin Edge, Wahoo computer, Hamerhead Karoo, Other ANT+ Compatible bike computer, or smartphone – These can communicate with SmartSense to view radar
alerts as well as the battery level of the system.
- Garmin Edge Power Mount – Charge or keep your Garmin Edge charged with the power mount.
Q - What is the battery life of the system?
A - This is completely dependent on the light mode used. The headlight mode has the largest effect on battery life. You should expect over 24 hours of operation in flashing modes, 10 hours with the light in solid low-beam, and 2.5 hours with the headlight at full brightness
Q - How do you charge the battery?
A - The SmartSense battery is charged while on the bike through the downtube or off the bike with a USB-C cable.
Q - Can I use the SmartSense battery to charge a smartphone?
A - Yes. Please note that depending on your device, one of the following steps might be required. This is to make the USB-C port completely inactive while it is not in use. This helps prevent any corrosion on the connector from moisture that might accumulate in the charge port.
- Plug the cable into the phone, then into the battery for this functionality.
- Double-press the button on the battery once the cable is connected to both devices.
Q - Can I use my SmartSense battery to charge a computer?
A - Yes, this should be possible, although your computer may still slowly discharge as it uses more power than the battery can supply.
Q - Can I charge my head unit from the SmartSense battery while riding?
A - This is possible for some Garmin Edge units with the Garmin Power Mount.
Q - What is the size (capacity) of the Battery?
A - 43.2Wh This is equivalent capacity to a 11,600mAh standard power bank at 3.7V.
Q - Does the SmartSense battery power SRAM AXS? Does AXS components still have their own batteries?
A - Yes, the SmartSense system powers the derailleurs on a SRAM AXS-equipped bike. The shifters still have their own coin-cell batteries which must be replaced occasionally.
Q - Does the SmartSense battery power Shimano Di2?
A - All SmartSense Gen. 2 bikes are equipped with Sram AXS shifting which is powered from the SmartSense battery, so you only have one battery to charge for your entire bike. SmartSense is not currently compatible with Shimano Di2.
Q - How much time does it take to fully charge a SmartSense battery?
A - From empty to a full charge with a charger of at least 20W, charging the battery takes roughly 2.5-3 hours. Less powerful chargers will take more time.
Q - What is the temperature range the battery can work in?
A - The battery can charge from 0 – 42C (32 – A - 107F) and operate from -7 – 55C (19 – 131F)
Q - What do the different colours around the charge port mean?
A – The colours indicate the battery’s state of charge.
Colours:
Green: 100%-61%
Yellow: 60%-31%
Red: 30%-6%
Flashing Red Once Per Second: 5%-0%
Pattern Meanings:
- Pulse: System is charging
- Blue & Red Flash: Battery protection mode – check your charging port for water or other contaminants. This can also be caused by extreme low or high temperatures.
- Green and Red Flashing: Permanent failure – please contact Cannondale customer support
RADAR
Q - How is the rider informed that a car is coming?
A - The radar data can be sent to ANT+ compatible cycling head units as well as the Cannondale app.
Q - What does a vehicle driver see when approaching and passing a rider with a SmartSense equipped bike?
A - Depends on the region. Most will see a change in the blink pattern and increased brightness. In Europe, due to STVZO regulations, there is no blink pattern.
Q - What do the different lights on the side of the radar mean?
- Flashing Purple – Device is in active pairing mode
- Single Blue Flash – Device is in smart sleep mode
- Double Blue Flash – Device is in active mode
- Flashing Yellow – Device is in demo mode
- Flashing Blue and Green Alternating – Device is applying a firmware update
- Flashing Green 10 Times – Device successfully applied a firmware update
- Flashing Red 10 Times – Device was unable to apply a firmware update
- Single Red Flash – The device is in active mode and is connected to a battery that is low
- Double Red Flash – The device is in smart sleep mode and is connected to a battery that is low
- Solid Green – Device is in mass storage mode
- Solid Red – An error occurred. You may need to restart the device
LIGHTS
Q - What is the maximum lumen output of the lights?
- Headlight – 800 lumens
- Taillight – 65 lumens
Q - Are the lights waterproof?
A - Yes, the taillight is rated IPX7. The headlight is rated IPX5.
Q - What lights are SmartSense compatible?
A - Currently, only the light that comes with the system is compatible with SmartSense Gen. 2. This was chosen as it gives the best balance of size, integration, and performance for riders.
Q – Can a saddle bag or tool roll fit with the taillight?
A - Your SmartSense Gen. 2 bike comes with the Cannondale StashPort and StashBag which can accommodate many of your tools and spares needed for riding. If this is not large enough, there are also mounting points for a top tube bag. If you would still prefer a saddle bag, GoPro extension arms are available from many retailers which can be used to move the light slightly and give space for a saddle bag.
SHIFTING
Q - What happens if my SmartSense battery dies? Can I replace the cable with an AXS battery?
A - The system was designed so that the shifting always works unless the battery is completely depleted. At low battery levels, the system will automatically turn off the lights and radar to make sure that shifting is still available. You can configure what battery percent this happens in the Cannondale app. Keep in mind that the SmartSense battery has roughly 20 times the capacity of a Sram AXS battery, so 5% battery on a SmartSense battery is equivalent to a fully-charged AXS battery. If you
still have concerns, the Sram AXS extension cable can be disconnected and replaced with a battery. However, the cable is connected to the battery near the bottom bracket of the bike and requires additional tools to disconnect. The cable would need to be held in place or removed to be prevented from getting caught in the wheel or drivetrain. So, if you feel the need to carry extra SRAM batteries, carry a few zipties as well.
SMARTSENSE : GEN 1 Vs GEN 2
Q - What is the difference between this version and the older version of SmartSense?
A - The new SmartSense system has all-new components. The battery has over twice the capacity, the headlight has twice the lumen output, and the radar and taillight are integrated into one device. Our focus was on better integration and performance rather than new features for this new version.
SmartSense
(Gen 1 vs. Gen 2)
Max International Lumens
350 vs 800
Battery Life at Max Power
2H 45M vs 4H 30M
Battery Life Flashing
~15H vs >24H
Battery Capacity
19.2WH vs 43.2WH
Powers Shifting
NO vs YES (SRAM ONLY)
Battery Location
EXTERNAL vs INTERNAL
Can be charged while riding?
NO vs YES
Battery w/ integrated flashlight?
NO vs YES
Light Mode Button Location
BACK OF HEADLIGHT vs SIDE OF TAILLIGHT
Q - What parts are backwards/forwards compatible?
A - The Garmin Power Mount is compatible with both generations of systems. Besides that, none of the 1st-generation SmartSense components can be added to the 2nd-generation system without error. The 2nd-generation eRTL which is available aftermarket from Garmin can be added to first-generation systems to replace the original radar and taillight. The new battery is incompatible with 1st-generation frames. The new headlight and shifting cables draw too much power than the first-generation battery can support and will cause error codes.
Q - What are new features for the 2nd-generation system?
A - SmartSense Gen. 2 now powers Sram AXS electronic shifting from the SmartSense battery. The battery also features a “glovebox light” and flashlight on the battery. All models now come with radar. Additionally, the system supports sharing battery percentage over the ANT+ light network standard. If you connect your cycling computer to the system to display radar, the battery percentage of the SmartSense system will show up accurately.
Q - Have any features been removed from the 1st-generation system for SmartSenseGen. 2?
A - To make the system the most integrated and compact as possible, we removed the handlebar-mounted radar display. This will mean that you will need to view radar info on a bike computer or the Cannondale app. Additionally, Cannaondale have removed the ambient light sensor which allowed the headlight to automatically adjust the brightness. This was also done to make the devices as compact as possible.
Q – If I purchase a Synapse without SmartSense, is it possible to add the SmartSense system later?
A – At this point, Cannondale are not offering the SmartSense Gen 2 system aftermarket. Only equipped on select Synapse models.