The Shimano Di2 (Digital Integrated Intelligence) system brings electronic shifting to a new level, offering precise, customisable gear changes. But what really sets Di2 apart are the various shifting modes it offers—Manual, Semi Synchronised (semi automatic), and Full Synchronised (automatic). These modes allow cyclists to either take full control of shifting or let the system assist in optimising shifts for smoother rides.
In this blog post, we’ll explore each Di2 shifting mode, explain how they work, and discuss when to use them. We’ll also touch on how the system’s lights provide crucial feedback about battery levels and shifting modes.
What is Shimano Di2 Synchronised Shifting?
Synchronised Shift refers to Shimano’s automatic shift modes within Di2 systems. Contrary to what some may think, Synchro Shift is not one mode but actually two distinct modes: Semi Synchronised Shift and Full Synchronised Shift. Each mode is designed to work differently, but both aim to optimise gear transitions for an efficient, seamless ride.
Semi Synchronised Shift (Default: S1)
In Semi Synchro Shift when you shift the front derailleur, Shimano Di2 automatically adjusts the rear derailleur to compensate. This prevents sudden, large changes in gear ratios, which can disrupt your pedalling rhythm. For example, if you downshift the front derailleur, the system will move the rear derailleur one or two gears to smooth out the transition.
This mode doesn’t automate front derailleur shifts like Full Synchro, but it reduces the jumps between gears, making it easier to maintain a steady cadence.
When to use Semi Synchro Shift:
Moderate climbs or rolling hills: When front derailleur shifts are necessary, but you want smoother transitions between gears.
Rides with frequent gear changes: This mode makes shifting more intuitive and easier without fully automating the process.
Benefits:
Reduces drastic gear jumps by compensating rear derailleur shifts when the front is adjusted.
Ideal for riders who want to keep control of the front derailleur but still benefit from a smoother shifting experience.
Full Synchronised Shift (Default: S2)
In Full Synchro Shift, Shimano Di2 automatically shifts your front derailleur when you make certain shifts on the rear derailleur. This ensures the derailleurs work together to maintain the best gear combination for the terrain.
According to Shimano, Full Synchro Shift doesn’t monitor your speed or cadence—it simply follows a predefined map of shift points. For instance, as you move through the rear cogs toward larger gears (e.g., from 11T to 28T), the system will shift your front derailleur from the big chainring to the smaller one between certain gear thresholds, like 21T to 25T. This shifting map can be customised according to your preferences.
When to use Full Synchro Shift:
Endurance rides: Ideal when you don’t want to worry about manual front derailleur shifts.
Rolling terrain: Allows you to focus on the ride rather than constantly adjusting both derailleurs.
Simplifying gear choices: Full Synchro takes over both front and rear derailleur management, reducing the number of decisions you need to make during shifting.
Triathlon bikes: Designed for setups where operating the front derailleur isn't as accessible or practical as it is on a standard road bike.
Benefits:
Simplifies gear management by automatically shifting the front derailleur.
Ensures an optimal gear combination for smoother cadence.
Allows you to concentrate more on your ride than on shifting.
Manual Mode (M)
Manual Mode is the simplest form of Di2 shifting. In this mode, you’re in full control of both the front and rear derailleurs. Every shift is manual, and you decide when and how to shift based on your preferences and terrain. This mode doesn’t use any of the automatic features found in the Synchro modes.
When to use Manual Mode:
Experienced riders: Cyclists who prefer complete control over every shift.
Technical terrain: Great for rides where you need to manage every gear shift carefully, like steep climbs or tricky descents.
Racing: Perfect for race scenarios where precise control is essential.
Benefits:
Complete control over all shifting decisions.
No automation, which may appeal to riders who prefer a more traditional approach.
Ideal for technical courses or riders who don’t need automated assistance.
Switching Between Modes
Switching between Manual, Semi Synchro, and Full Synchro modes is simple but can't be done while riding (unless you have an 11-speed Di2 system).
To switch between modes, double-click the button on the charging port for 11-speed Di2 systems, or use the button on the rear derailleur for 12-speed systems. The sequence cycles from Manual to Semi Synchro (S1), then to Full Synchro (S2), and pressing again returns it to Manual mode.
Shimano Di2 uses light indicators to keep you informed about both your shifting mode and battery level. Here’s how to interpret the lights:
When clicking once the function button | 11-Speed Di2 Systems | 12-Speed Di2 Systems |
Battery Mode Indicator (will be displayed first) | Green light: Battery is above 50% capacity.
Flashing green light: Battery is between 25% and 50%. Red light: Battery is below 25%, so it’s time to charge soon. Flashing red light: Critical battery level, meaning shifts will soon be disabled. | Green light: Battery is above 50% capacity.
Flashing green light: Battery is between 25% and 50%.
Red light: Battery is below 25%, so it’s time to charge soon.
Flashing red light: Critical battery level, meaning shifts will soon be disabled. |
Shift Mode Indicator | Solid green light: Manual Mode is active.
Solid red light: Semi Synchro Mode is active.
Flashing red light: Full Synchro Mode is active. | Solid blue light: Manual mode is active. Two blue light flashes: Semi Synchro mode is active. Three blue light flashes: Full Synchro mode is active. |
Final Thoughts
The Shimano Di2 system offers a versatile range of shifting options that cater to all types of cyclists. Whether you want full control with Manual Mode or prefer the convenience of Full or Semi Synchro Shift, there’s a mode for every rider. Combined with easy-to-read light indicators for battery and shifting modes, Di2 takes the guesswork out of riding, allowing you to focus more on the road ahead.
By experimenting with each mode, you’ll be able to find the perfect balance that suits your personal riding style, making every ride smoother and more enjoyable.
Both Semi Synchro and Full Synchro modes can be fully customised to suit your preferences. If you have any questions or need assistance with setup, don’t hesitate to book a service with our workshop.
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