The Shimano SM-BB6700 [paid link] bottom bracket is a trusted component in the Ultegra series, known for its reliability, sealed cartridge bearings, and compatibility with Hollowtech II cranksets. However, improper installation practices can undermine its performance, reduce its lifespan, or even damage the frame. This guide focuses specifically on the SM-BB6700 [paid link] model and highlights the most common installation mistakes that road cyclists and mechanics should avoid. Whether you’re fitting it on a new build or replacing a worn-out unit, understanding these pitfalls is essential for optimal function and durability.
Tools Required:
- Hollowtech II bottom bracket installation tool
- Torque wrench [paid link]
- 5mm Allen key
- Grease (anti-seize compound or Shimano-recommended)
- Bottom bracket facing tool (optional but recommended for metal frames)
- Clean cloth and isopropyl alcohol for cleaning threads
Frame Preparation Errors
One of the first mistakes installers make is neglecting proper frame preparation. The SM-BB6700 [paid link] is a threaded bottom bracket designed for English-threaded (BSA) 68mm bottom bracket shells. Ensuring the frame shell is correctly prepared is not just good practice—it’s essential.
Many overlook cleaning and inspecting the bottom bracket shell threads for debris, corrosion, or manufacturing imperfections. Installing the bottom bracket into a dirty or misaligned shell can cause cross-threading, creaking, and long-term wear. Aluminum and steel frames may benefit from re-facing and chasing the threads before installation. While carbon frames with aluminum inserts are less likely to need facing, they still require thorough inspection and cleaning.
Avoid using threadlockers on this model unless explicitly specified by Shimano. Instead, use high-quality grease or anti-seize on the threads to prevent galvanic corrosion and ease future removal.
Over-Torquing or Under-Torquing the Cups
Torque specification for the SM-BB6700 cups is 35–50 Nm. Improper torque application is a widespread error that can lead to serious issues.
Under-torquing can cause the cups to back out over time, which may lead to lateral crank play and creaking under load. On the other hand, over-torquing can strip the threads, crush the bearing seals, or even deform the bottom bracket shell if the frame is made from softer materials.
Always use a calibrated torque wrench [paid link] with the correct adapter to ensure the cups are tightened within Shimano’s recommended range.
Bearing Alignment Problems
Improper alignment of the bottom bracket cups during installation can lead to uneven bearing loading. This is particularly problematic with the SM-BB6700 due to its tight bearing tolerances and narrow spacing designed for Hollowtech II cranksets.
Misalignment can occur if cups are installed without maintaining parallel orientation, especially in older or damaged frames. If the frame shell is slightly ovalized or improperly faced, the bearings will not sit flush. This often results in stiff crank rotation or accelerated bearing wear.
A bottom bracket press is not required for the SM-BB6700, but installers must still take care to thread both cups evenly and gradually, alternating sides if necessary to keep alignment true.
Installing Without Greasing Interfaces
Skipping grease application during installation is a frequent error that can lead to creaking and corrosion. The SM-BB6700 relies on proper lubrication at multiple interfaces:
- Threaded cups to frame shell
- Crank spindle to bottom bracket bearings
- Bearing preload adjuster (plastic ring) to crank arm
Each of these points requires a specific type of grease. General-purpose bike grease is suitable for the threads, while a thicker assembly compound may be beneficial at the crank spindle interface to prevent micro-movement and creaking.
Failure to apply grease can also lead to galvanic corrosion between dissimilar metals—particularly between aluminum cups and steel frames or inserts.
Incorrect Crank Arm Preload Adjustment
The SM-BB6700 bottom bracket is used with Shimano Hollowtech II cranksets, which utilize a non-drive side crank arm fixing bolt and plastic preload cap.
A common mistake is over-tightening the preload cap or neglecting to adjust it altogether. Over-tightening puts axial pressure on the bearings, which restricts rotation and can cause premature bearing failure. Not tightening it enough allows play in the crankset, which manifests as knocking or lateral movement.
The preload cap should be tightened until it’s snug but still allows free crank rotation. This is best done using Shimano’s plastic preload tool or a properly designed aftermarket equivalent.
Neglecting Frame Compatibility and Wear
While the SM-BB6700 is compatible with English-threaded shells, it’s important to confirm the exact bottom bracket shell type and width on your frame. Some older Italian-threaded frames or newer press-fit shells are not compatible.
Also, failing to inspect the shell for damage or wear from previous bottom brackets is a common oversight. Scored or damaged threads may not hold the cups securely, and excessive shell width variation can prevent proper bearing seating.
Before installation, measure the width of the bottom bracket shell with calipers and inspect the threads closely. If in doubt, consult with a framebuilder or experienced mechanic.
Using Aftermarket Cups or Spacers
Though tempting, using non-OEM cups or spacers with the SM-BB6700 can lead to mismatched bearing preload, misalignment, or sealing issues. Shimano has designed this model with precise tolerances, and deviation from those specs can reduce performance.
For frames that require spacing adjustments—such as 73mm shells—always refer to Shimano’s installation documents to confirm which spacers are required and in what order they must be installed.
Conclusion
Proper installation of the Shimano SM-BB6700 bottom bracket is critical for drivetrain efficiency, crankset stability, and long-term bearing health. Avoiding the above mistakes ensures your bottom bracket performs quietly and reliably over thousands of miles.