The Shimano CS-6700 [paid link] cassette, part of the Ultegra 6700 series, is a high-performance road bike component designed to deliver smooth, reliable shifting under a range of riding conditions. However, as with any drivetrain part, compatibility is crucial for optimal performance. Misalignment between components can lead to subpar shifting, increased wear, and frustrating maintenance cycles. This article explores in detail the compatibility boundaries of the CS-6700 [paid link], offering a guide to what works seamlessly, what fails outright, and what riders should avoid when integrating this cassette into their drivetrain.
Understanding the CS-6700 Cassette Architecture
The CS-6700 [paid link] is a 10-speed cassette, built with a blend of steel sprockets and alloy carriers. It was originally designed for Shimano’s 10-speed Ultegra groupset and is optimized for road performance. Gear ranges include 11-23T, 11-25T, 11-28T, 12-25T, and 12-30T, providing riders with flexibility for various terrains and riding styles.
The spline interface is Shimano’s traditional Hyperglide (HG) system, and its design supports precise chain engagement for fast, clean shifting. The cassette uses a standard Shimano 10-speed freehub body, which becomes the foundation of its compatibility profile.
Compatibility with Shimano Freehub Bodies
The CS-6700 fits on any Shimano or Shimano-compatible 10-speed freehub. This includes road-specific freehubs as well as some MTB options from the same era. However, riders must verify the following:
- Road Freehub Bodies (10-Speed Specific): Directly compatible without spacers.
- 11-Speed Road Freehub Bodies: Requires a 1.85 mm spacer to accommodate the narrower width of the 10-speed cassette.
- MTB Freehubs (Pre-Micro Spline): Can be compatible if using a 10-speed spacing configuration, though not ideal for road setups.
What fails: Mounting on SRAM XD [paid link] or Shimano Micro Spline hubs is not possible without proprietary adapters, which are not recommended for road drivetrains due to spacing and engagement inconsistencies.
Chain Compatibility and Shifting Performance
The CS-6700 cassette is specifically designed for use with 10-speed Shimano chains. This ensures synchronized indexing, accurate cog spacing, and minimal drivetrain wear. Compatible options include:
- Shimano CN-6701 [paid link] (Ultegra 10-speed chain)
- Shimano CN-7901 (Dura-Ace 10-speed chain)
- KMC X10 Series (aftermarket, known for durability)
Using 11-speed chains on a CS-6700 cassette may work temporarily, but it introduces slight misalignments in cog spacing, resulting in hesitant or noisy shifting under load.
What fails: 9-speed or 11-speed chains. While they may “fit,” shifting precision suffers, and long-term use can cause uneven wear across the cassette teeth.
Rear Derailleur Compatibility
The CS-6700 cassette functions best when paired with Shimano 10-speed road derailleurs, particularly the Ultegra RD-6700 [paid link]. Compatibility extends to other Shimano 10-speed road derailleurs (e.g., 105 5700 or Dura-Ace 7900), but the derailleur must match the cassette’s maximum tooth count.
- Short cage (SS) derailleur: Supports up to 28T
- Medium cage (GS) derailleur: Required for 30T sprockets
What fails: Pairing the CS-6700 with 11-speed derailleurs often leads to misaligned indexing, as cable pull ratios differ slightly. Similarly, 9-speed or MTB-specific derailleurs will not provide accurate gear changes due to variance in geometry and actuation.
Shifter Compatibility
Only 10-speed Shimano STI shifters are guaranteed to work correctly with the CS-6700. This includes:
These shifters are calibrated to move the derailleur the correct amount per shift for 10-speed spacing.
What fails: Using 11-speed shifters introduces too much movement per click, while 9-speed options result in under-travel. Even minor mismatches lead to ghost shifting and inconsistent gear engagement.
Cross-Brand Compatibility Considerations
While Shimano’s 10-speed standard is relatively open, not all third-party cassettes and drivetrains align well with the CS-6700. Consider these findings:
- SRAM 10-Speed Drivetrains: Mostly compatible due to similar cog spacing, but micro-differences in actuation can still produce minor shifting anomalies.
- Campagnolo 10-Speed: Not compatible. Different freehub design, cog spacing, and indexing system entirely.
What fails: Cross-brand cassette pairing with Campagnolo systems. Even with conversion hubs, the mismatch in cog alignment and actuation makes it unreliable.
Wheelset Compatibility
Any 700c road wheelset with a Shimano 10-speed freehub body will accommodate the CS-6700. For newer wheelsets designed for 11-speed cassettes, a 1.85 mm spacer must be added before installation.
What fails: Wheelsets built exclusively for SRAM XD [paid link], XDR [paid link], or Campagnolo freehub bodies are not compatible unless the freehub is replaced—a costly and often unnecessary step.
Cassette Alternatives and Interchangeability
If replacing the CS-6700 is necessary, compatible alternatives include:
- Shimano 105 CS-5700 [paid link]: Same gear spacing, slightly heavier.
- Shimano Tiagra CS-4600 [paid link]: Budget-friendly, also compatible.
- Shimano Dura-Ace CS-7900 [paid link]: Lighter and stiffer, suitable for performance upgrades.
What to avoid: Jumping to an 11-speed cassette without overhauling the derailleur, shifters, and freehub. Partial upgrades are a common mistake that undermines the drivetrain’s integrity.
Conclusion
The Shimano CS-6700 cassette is a precise component with strict compatibility guidelines. Optimal performance is achieved when all drivetrain components—chain, shifters, derailleurs, and hub—align with the 10-speed Shimano road standard. Deviating from these standards can lead to poor shifting, accelerated wear, and mechanical issues.
Understanding these compatibility secrets ensures that riders maintain peak performance, reduce drivetrain noise, and enjoy consistent gear changes on every ride.