Shimano Ultegra ST-6600G Shifters

The Shimano Ultegra ST-6600G STI shifters are a prime example of a classic, high-quality component from a specific era of road cycling. Here is a breakdown of the industry information and compatibility.

• Market Position: The Ultegra 6600 groupset, launched around 2005, was Shimano’s second-tier road offering. It was considered the “sweet spot” for many cyclists, providing a substantial amount of the performance and technology from the top-tier Dura-Ace 7800 groupset at a much more accessible price point. The Ultegra 6600 series was praised for its durability, smooth-shifting performance, and ergonomic design.
• The “G” Designation: The “G” in ST-6600G stands for “Gray” or “Ice Gray.” This was a specific cosmetic variation of the standard ST-6600 shifter, which had a slightly darker, polished finish. This cosmetic difference was sometimes paired with other components from the “Ultegra SL” groupset, which was a lighter version of the standard 6600 series.
• STI (Shimano Total Integration): These shifters are a classic example of Shimano’s STI system, which combines the brake and shift levers into a single unit. This design was revolutionary in the 1990s and became the industry standard for road bikes. The ST-6600 shifters feature a single large brake lever for braking and a smaller lever behind it for upshifting, with a button on the side for downshifting.
• Hidden Cables: A key feature of the 6600 series was the repositioning of the shift cables. Unlike the previous 9-speed shifters, the cables for the 6600 series were routed underneath the handlebar tape, providing a cleaner, more aerodynamic look and a more comfortable grip for the rider.

Compatibility

Compatibility is a critical consideration for these shifters, as they are part of a closed-system design.

• Drivetrain Speeds: The ST-6600G shifters are designed for 10-speed drivetrains only. They will not work with 9-speed, 11-speed, or 12-speed components.
• Rear Derailleur: The shifters must be paired with a Shimano 10-speed road rear derailleur. They have a specific cable pull ratio that is unique to Shimano’s 10-speed road systems. They are not compatible with older 9-speed derailleurs or with mountain bike derailleurs (which have a different pull ratio).
• Front Derailleur: The ST-6600G shifters came in two main versions:
  • ST-6600: The standard double shifter for use with a 2×10 drivetrain (two chainrings in the front).
  • ST-6603: The triple shifter for use with a 3×10 drivetrain. The ST-6600G refers specifically to the double version. The left shifter is indexed to work with a double crankset and is not compatible with a triple without significant compromises.
• Brakes: The brake levers are designed for Shimano “Super SLR” road caliper brakes. While they will physically pull the cable on other brands of caliper brakes, the lever’s mechanical advantage is optimized for a Shimano brake from the same era (like the Ultegra BR-6600). They are not compatible with V-brakes, mini V-brakes, or disc brakes.
• Aftermarket: Shimano has discontinued the 6600 series and its components. The shifters are now an aftermarket item, sought after by collectors, restorers, and riders who need a replacement part for a bike with a working 10-speed drivetrain. Finding new old stock (NOS) or well-maintained used shifters can be a challenge.