The Shimano SM-BB93 [paid link] bottom bracket is a high-quality, lightweight threaded press-fit model designed primarily for road bike applications using Hollowtech II cranksets. Despite its precision engineering, riders occasionally encounter setup issues that can lead to premature wear, creaking, or inefficient power transfer. This troubleshooting guide addresses the most frequent problems experienced during and after installation of the SM-BB93 [paid link], with expert advice on resolving and preventing them for optimal drivetrain performance.
Understanding the SM-BB93 [paid link] Design and Function
The SM-BB93 bottom bracket is part of Shimano’s Hollowtech II system, which allows for an external bottom bracket shell combined with a 24mm spindle. Its sealed cartridge bearings are pre-lubricated and integrated into a lightweight composite cup. While this makes installation straightforward, precision alignment and torque accuracy are essential to prevent long-term mechanical issues.
The component is compatible with standard BSA (British Standard Thread) bottom bracket shells and is designed specifically for road bikes with narrower shell widths (68mm). Its narrow profile reduces weight, but this compactness demands high precision during assembly.
Common Set-Up Issues and How to Fix Them
1. Creaking or Clicking Noises Under Load
One of the most reported issues with the SM-BB93 is a persistent creaking sound when pedaling hard. This noise often stems from incorrect torque, dirt contamination, or uneven frame interface.
Solution
Ensure the bottom bracket shell is thoroughly cleaned and faced. Apply high-quality grease to both the threads and cup interfaces. During installation, torque the bottom bracket cups to Shimano’s recommended 35-50 Nm. If the creaking persists, remove the crankset, clean all interfaces, and re-torque the crank bolts to 12-14 Nm.
2. Misalignment of Bearing Cups
Improper facing or cross-threading during installation can cause misalignment, resulting in increased drag or uneven wear on the bearings.
Solution
Use a bottom bracket facing tool to confirm that the shell faces are square. If facing tools aren’t accessible, consult a professional mechanic. Reinstall the cups with proper anti-seize compound and thread engagement to avoid cross-threading. Always hand-thread first before applying torque.
3. Bottom Bracket Loosening Over Time
In some setups, the cups may become loose, particularly on bikes with less robust threading tolerances or aggressive torque from riders.
Solution
Use a threadlocker (such as medium-strength Loctite 243) on the threads if repeated loosening occurs. Check for any frame shell damage or wear, which can reduce thread engagement strength. Retorque both sides after the first 100 km post-installation to ensure the assembly remains secure.
4. Water Ingress and Bearing Contamination
Despite its sealed bearing design, the SM-BB93 is vulnerable to water ingress, especially during frequent riding in wet conditions or improper washing.
Solution
Disassemble the crankset periodically to inspect for moisture. If water or grime is found, dry the area and reapply waterproof grease around the bearing seals. Adding a neoprene crank arm seal or rubber boot can help improve water resistance.
5. Excessive Bearing Drag
Riders may feel tightness or resistance in the crank rotation, particularly after installation or during colder months. This is typically due to overtightened crank bolts or factory grease stiffening in low temperatures.
Solution
Loosen the crank arm preload cap and adjust it so that there is no lateral play but the crank rotates freely. Avoid overtightening. Replace the factory grease with a lighter bearing lubricant if the stiffness persists in cold environments.
Preventing Set-Up Issues: Best Practices
- Always use Shimano-specific bottom bracket tools for cup installation (e.g., TL-FC32 [paid link] or TL-FC36 [paid link]).
- Clean and inspect the shell threads and faces before each installation.
- Use a torque wrench [paid link] to ensure precise torque application.
- Apply grease or threadlocker where appropriate to reduce noise and increase stability.
- Check crankset and spindle condition—worn interfaces can transmit noise or cause bearing wear.
When to Replace the SM-BB93
If bearing play develops, or if the crank no longer rotates smoothly despite lubrication, it’s time to replace the bottom bracket. Unlike serviceable models, the SM-BB93 does not allow for bearing replacement alone; the entire unit must be swapped out.
Check for wear every 3,000–5,000 km under normal conditions, or more frequently in muddy, wet, or high-load usage scenarios.
Conclusion
Troubleshooting the SM-BB93 bottom bracket starts with understanding its design and the precision it demands. Many issues, such as creaking, drag, or loosening, stem from incorrect installation practices or poor frame preparation. By adhering to Shimano’s torque specifications, using the right tools, and maintaining a clean and well-lubricated assembly, riders can eliminate common problems and extend the life of their SM-BB93 bottom bracket. With proper care, this component delivers quiet, efficient power transfer across countless miles of road riding.