Indexing is the predetermined, incremental movement of a derailleur that corresponds with each click of a shifter. When a derailleur is activated, either by a mechanical shifter tensioning or releasing a cable or the Di2 button to activate derailleur motors, the component will move the chain from cog to cog on the rear cassette or different chainrings in the front. SIS derailleurs and shifters are designed to move a specific amount to achieve accurate and reliable gear changes every time.

The introduction of indexed shifting by SHIMANO, and the subsequent evolution of the SIS technology over the decades, defined the reliable and enjoyable ride experience that most of us take for granted today. Gone are the days of knee-shifting the downtube levers in the middle of a field sprint or fiddling to find the right gear during a critical section of trail.

SHIMANO Indexed Shifting means that a properly adjusted system will deliver the right gear at critical moments over and over again. It saves energy, allowing riders to focus on responding to attacks during a race, picking perfect lines through roots and rocks, or just cruising along while enjoying the ride.

When SHIMANO introduced indexed shifting, it meant that riders using a properly adjusted system could rely on consistent and accurate gear shifts with the push of a button. Indexing effectively calibrated the entire drivetrain to deliver the same shifts every time due to the newly engineered consistency of derailleur movement.

The added precision and reliability of the SIS technology also allowed SHIMANO to push the boundaries of rear gearing, leading to the advent of 9-, 10-, 11- and 12- speed cassettes over the years. Without the precision of SHIMANO's shift technology, the tight tolerances of 12-speed shifting would not be a reality.

The introduction of indexed shifting by SHIMANO, and the subsequent evolution of the SIS technology over the decades, defined the reliable and enjoyable ride experience that most of us take for granted today. Gone are the days of knee-shifting the downtube levers in the middle of a field sprint or fiddling to find the right gear during a critical section of trail.

SHIMANO Indexed Shifting means that a properly adjusted system will deliver the right gear at critical moments over and over again. It saves energy, allowing riders to focus on responding to attacks during a race, picking perfect lines through roots and rocks, or just cruising along while enjoying the ride.

changed the very experience of riding a bicycle for the better, and this technology continues to evolve year after year on every SHIMANO drivetrain.