SM-BB6700 Compatibility Secrets: What Works, What Fails, and What to Avoid

Posted on
in No category

The Shimano SM-BB6700 [paid link] bottom bracket is a high-performance component designed specifically for road bikes using the Hollowtech II crank system. As part of Shimano’s Ultegra 6700 series, this bottom bracket is engineered for durability, efficiency, and compatibility with top-tier drivetrains. However, like many bottom brackets, its compatibility is not universal. Misunderstanding what works—and what doesn’t—can lead to suboptimal performance, premature wear, or even mechanical failure.

In this guide, we’ll break down the compatibility specifics of the SM-BB6700 [paid link], what systems it integrates well with, and how to avoid common mistakes during setup and component matching.

Understanding the SM-BB6700 Design Philosophy

The SM-BB6700 is based on Shimano’s Hollowtech II standard, a system that merges the bottom bracket bearings externally to the frame to improve stiffness and weight distribution. This design is tailored for 68mm English-threaded bottom bracket shells, most commonly found on road bikes from the mid-2000s through the early 2010s.

With anodized aluminum cups, durable sealed bearings, and precise Japanese threading, the SM-BB6700 is optimized for Ultegra-level [paid link] performance. It’s compatible with Hollowtech II 24mm spindle cranksets and designed to reduce flex under load while offering long-lasting smooth rotation.

Compatible Cranksets: What Works Well

The SM-BB6700 is highly specific in what it pairs with—mainly Shimano’s Hollowtech II road cranksets. Here’s what you can confidently install with this bottom bracket:

  • Shimano Ultegra 6700 cranksets – This is the native match for the SM-BB6700. Tolerances and bearing alignment are perfect when used together.
  • Shimano 105 (5700, 5800 series) – While not the Ultegra tier, these cranksets share the same 24mm spindle diameter and are compatible both mechanically and dimensionally.
  • Shimano Dura-Ace 7900, 7800 – These high-end cranksets share the same Hollowtech II interface and work flawlessly with the SM-BB6700.
  • Shimano Tiagra (4600 series and newer) – Later Tiagra versions moved to Hollowtech II and are compatible in terms of axle diameter and width.

Importantly, while these cranksets differ in material and finish, their interface dimensions remain standardized, allowing cross-series integration without performance compromise.

Frame Compatibility: Which Bottom Bracket Shells Fit

The SM-BB6700 requires a 68mm or 70mm BSA (British Standard Thread) shell, also known as English threading. These are the most common threaded standards and can be identified by:

  • Shell width: 68mm (standard road) or 70mm (some Italian frames, with caution).
  • Thread type: 1.37 x 24 TPI (for BSA). Note that while 70mm shells are often Italian-threaded, Shimano’s design supports some 70mm cases due to tolerance allowances, but caution is needed.

Avoid installing this bottom bracket in press-fit frames (BB86, BB90/92, PF30 [paid link], or BB30) unless you use conversion adapters, which introduce risk of bearing misalignment and increased drag.

What Fails: Incompatible Setups and Common Pitfalls

Several compatibility failures stem from assuming all Shimano parts fit together or from using poorly-matched aftermarket parts. Here’s what to avoid:

  • Press-Fit Frames Without Adapters – Attempting to fit an SM-BB6700 into a press-fit shell without an adapter will not only fail mechanically but may damage the frame or the component.
  • 24mm to 30mm Cranksets – Cranksets from SRAM DUB [paid link] or other 30mm spindle systems are incompatible without elaborate—and often unreliable—conversion kits.
  • Non-Hollowtech II Cranks – Square-taper or Octalink cranks won’t interface with this bottom bracket. Likewise, Shimano’s older designs or MTB-specific cranks may not align properly.
  • Mixing Italian-threaded shells – While some Italian-threaded shells are 70mm wide, the threading direction is different (especially on the drive side). This will cause cross-threading and irreversible damage.

What to Avoid in Component Pairing

The SM-BB6700 is not designed for broad multi-platform use. Avoid these scenarios to maintain drivetrain performance and avoid premature wear:

  • Ceramic bearings from third-party brands – Though often advertised as upgrades, many third-party bearing kits don’t seat well in the Shimano cups or offer worse tolerances.
  • Using MTB cranksets – Mountain bike cranks often have different Q-factors and may not fit properly with road geometry, leading to chainline issues.
  • Incorrect installation tools – Use the Shimano TL-FC32 [paid link] or compatible Hollowtech II tool. Improper installation torque or tool slippage can damage bearing surfaces.

Drivetrain Pairing Considerations

Even when the crankset and bottom bracket are physically compatible, the rest of the drivetrain must also be considered. For optimal function:

  • Match chainring spacing and chain width – The SM-BB6700 supports 10-speed drivetrains. Using 11- or 12-speed chains may cause noise or inconsistent shifting.
  • Chainline alignment – When using compatible cranksets, ensure that the chainline remains within Shimano’s 43.5mm standard. Deviation affects front derailleur performance.
  • Derailleur compatibility – Pairing with a Shimano 10-speed front derailleur ensures crisp shifting. Mixing speeds or brands (like Campagnolo) can introduce lag or rub.

Using Adapters: When Necessary but Risky

Some mechanics and riders attempt to adapt the SM-BB6700 for press-fit systems using conversion kits. While this may work short-term, it often leads to:

  • Bearing misalignment
  • Increased drag
  • Creaking or frame wear
  • Reduced bearing life

Only use high-precision adapters from reputable brands if absolutely necessary—and only if you fully understand the tolerance stack-up involved.

Conclusion: Choose Wisely for Optimal Performance

The SM-BB6700 is a robust, reliable bottom bracket that performs best when used with Shimano Hollowtech II cranksets and threaded road bike frames. Compatibility is precise but not universal. Before installation, confirm crankset type, shell threading, and frame width. Avoid mixing with non-Hollowtech systems or attempting risky adaptations. Proper matching not only ensures optimal performance but significantly extends the lifespan of both the bottom bracket and crankset.