Shimano Ultegra 10-speed Cassette

The Shimano Ultegra 10-speed CS-6600 14-25t cassette is a component that represents a key period in road cycling history and holds a specific place in today’s aftermarket.

Industry Information

• Market Position: The Ultegra 6600 groupset, launched in the mid-2000s, was Shimano’s second-tier road offering. It was considered the “sweet spot” for many cyclists, providing a reliable blend of performance, durability, and a clean aesthetic at a much more accessible price point than the Dura-Ace 7800 groupset. The 6600 series was praised for its smooth shifting and durable construction, making it a “workhorse” for serious amateurs, racers, and enthusiasts alike.
• A “Close Ratio” Cassette: The 14-25t gearing is what’s known as a “close-ratio” cassette. This means the jumps between each cog are very small (e.g., 14-15-16-17-18-19-21-23-25). This tight spacing allows a rider to maintain a consistent, efficient cadence without large changes in pedaling effort, which is ideal for flat courses, rolling terrain, or racing where maintaining speed is critical. It is not designed for steep climbs, where a wider-range cassette (like an 11-28t or 11-32t) would be more suitable.
• Hyperglide (HG) Technology: The cassette features Shimano’s renowned Hyperglide technology. This involves specifically shaped teeth and ramps on the cogs to facilitate smooth, rapid, and quiet shifting, particularly under load.
• Construction: The CS-6600 cassette was made with durable, nickel-plated steel cogs. Unlike some of the higher-end Dura-Ace cassettes of the time, it did not have a titanium cog or a lightweight alloy spider, which contributes to its reputation for durability and longevity.

Compatibility

Compatibility is crucial for this cassette, as it is designed for a specific drivetrain system.

• Drivetrain Speeds: The CS-6600 is a 10-speed cassette. It is designed to work exclusively with a 10-speed chain and 10-speed road shifters and rear derailleurs from Shimano. It is not compatible with 9-speed, 11-speed, or 12-speed components.
• Freehub Body: The cassette is compatible with the standard Shimano/SRAM HG (Hyperglide) freehub body. This is a significant advantage, as it will fit on a vast number of road wheels from the past several decades. This is a “road” specific cassette and a 1.0mm spacer is required on most 10-speed HG freehubs to ensure proper fit.
• Derailleur Compatibility: For optimal performance, the cassette must be used with a 10-speed road rear derailleur. While the 14-25t range is small enough to be handled by both short-cage and mid-cage derailleurs, it is most commonly used with a short-cage derailleur in a double crankset setup.
• Chain: The cassette is designed to be used with a 10-speed road chain, such as the Shimano CN-6600 or CN-7801. Using a chain from a different speed or a different brand may lead to subpar shifting performance or premature wear.

Important Note: It is specifically noted in some older Shimano compatibility charts that some CS-6600 cassettes with 13, 14, 15, or 16-tooth top cogs are not compatible with Dura-Ace FH-7800 hubs or WH-7800 wheels. This is a specific exception to general Shimano compatibility that is important to note for those working on period-correct Dura-Ace builds.

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Cog: Shimano Ultegra 10-speed CS-6600 Cassette