The Shimano SM-BB93 [paid link] bottom bracket is a high-performance, lightweight, threaded bottom bracket designed specifically for road bikes running Shimano Hollowtech II cranksets. Renowned for its low weight and smooth operation, it’s a favorite among road cyclists looking for precision and durability. However, even a premium bottom bracket like the SM-BB93 [paid link] can suffer from poor performance or premature wear if not installed correctly. This guide focuses on the most common installation mistakes users make with the SM-BB93 [paid link]—and how to avoid them for a flawless setup.
Improper Shell Preparation: The Foundation of Most Failures
One of the most overlooked aspects of bottom bracket installation is proper frame shell preparation. The SM-BB93 is engineered to exact tolerances and requires a clean, properly faced and chased BSA-threaded bottom bracket shell for optimal fit.
If the shell is not correctly faced, bearing misalignment may occur. Misalignment leads to uneven load distribution across the bearings, accelerating wear and increasing drag. Additionally, if the threads aren’t chased, improper threading can result in cross-threading or insufficient engagement, risking loosening under pedaling torque.
Before installing the SM-BB93:
- Inspect the frame shell thoroughly.
- Ensure it is faced and chased using the appropriate tools.
- Remove any paint or debris from the threads to guarantee full engagement.
Skipping Grease or Anti-Seize on Threads
A common but critical error is installing the SM-BB93 dry. The threads must be coated with either high-quality bicycle-specific grease or anti-seize compound. This not only prevents galvanic corrosion (especially important with aluminum cups and steel frames) but also ensures proper torque application and future removal.
Without grease:
- Bottom bracket cups may seize into the frame over time.
- Creaking and noise issues often emerge after a few hundred kilometers.
- Torque readings can become inaccurate, leading to overtightening or undertightening.
Incorrect Torque Settings
Applying the correct torque to the SM-BB93 is crucial for longevity and performance. Shimano specifies a torque range of 35–50 Nm for BSA bottom brackets. Many home mechanics either under-tighten (leading to loosening during rides) or over-tighten (which can damage the cups or deform the frame threads).
Use a calibrated torque wrench [paid link] and follow Shimano’s installation specs precisely. Always tighten both cups evenly, starting with the drive side.
Using the Wrong Tools
Attempting to install the SM-BB93 using generic tools or tools designed for other bottom bracket types is a recipe for misalignment and component damage. Shimano’s TL-FC32 [paid link] or TL-FC36 [paid link] tools are designed specifically to interface with the notched cups of the SM-BB93.
Using incorrect tools can lead to:
- Rounding off the cup edges.
- Uneven torque distribution.
- Difficulty in achieving proper thread engagement.
For best results, always use the specified Shimano tools or high-quality equivalents from trusted third-party manufacturers.
Installing on an Incompatible Frame
The SM-BB93 is only compatible with BSA (English-threaded) 68mm bottom bracket shells. Attempting to fit it into frames with Italian-threaded shells, press-fit standards like BB86 or BB30, or T47 shells will not only fail but may also damage the frame or bottom bracket.
Check your frame’s specification before purchasing or attempting installation. If your frame uses a press-fit standard, look into Shimano’s press-fit compatible bottom brackets like the SM-BB92 instead.
Failing to Properly Preload the Crankset
The bottom bracket is just one part of the drivetrain interface. Once the SM-BB93 is installed, the Hollowtech II crankset must be fitted with appropriate bearing preload using the preload cap.
Neglecting this step, or over-tightening the preload cap, can result in:
- Excessive bearing drag.
- Premature bearing wear.
- Crank arm play or lateral movement.
Shimano provides a simple plastic preload tool for this purpose. Tighten the cap until light resistance is felt, then secure the crank arm bolts to spec.
Reusing Damaged or Contaminated Components
In some cases, riders attempt to reinstall an old SM-BB93 after contamination or impact damage. Reusing a bottom bracket that shows signs of water ingress, rust, or bearing play is ill-advised.
Signs of a compromised SM-BB93 include:
- Grinding or rough rotation when turning the bearings by hand.
- Rust or pitting on bearing seals.
- Lateral crank movement when the bottom bracket is under load.
Install only new or confirmed-good SM-BB93 units. The bearings are not serviceable, so internal damage means replacement is the only option.
Ignoring Thread Engagement and Cup Orientation
The SM-BB93 has a left-hand thread on the drive side and a right-hand thread on the non-drive side. Installing the cups on the wrong sides or forcing them in the incorrect direction can destroy the threads.
Always check:
- Drive-side cup (left-hand thread): turn counter-clockwise to tighten.
- Non-drive side cup (right-hand thread): turn clockwise to tighten.
Use thread direction indicators on the cups to guide correct installation.
Conclusion
Correctly installing the Shimano SM-BB93 bottom bracket is essential for achieving smooth, reliable performance and long component life. Mistakes like improper shell preparation, incorrect torque, using the wrong tools, or failing to follow thread direction can lead to serious issues ranging from noise to component failure.
By following Shimano’s specifications and avoiding these common pitfalls, cyclists can ensure their SM-BB93 performs as intended—delivering the efficient, durable crankset support that Shimano engineered it for.