How to Replace the Cable on Your SM-BB93 for Better Performance

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The Shimano SM-BB93 [paid link] is a premium bottom bracket designed specifically for use with Hollowtech II road cranksets. While bottom brackets like the SM-BB93 [paid link] don’t utilize traditional cables in the same way as derailleurs or brakes, it’s crucial to understand that some users mistakenly associate internal bottom bracket shell cable routing with the bottom bracket itself. This guide will clarify that distinction and focus on maintaining and replacing components related to or affected by the SM-BB93 [paid link], such as internal routing systems that pass near or through the bottom bracket shell.

If you’re experiencing shifting issues or drop in drivetrain performance and suspect a bottom bracket area cable issue, it may involve the front derailleur cable routing, which can pass beneath or near the bottom bracket shell. Here’s how to correctly service and replace these cables without compromising the integrity or performance of the SM-BB93 bottom bracket.

Understanding the SM-BB93 and Internal Cable Routing

The SM-BB93 is a threaded bottom bracket for BSA (British Standard Thread) frames with 68 mm or 73 mm shell widths. It features high-quality seals and bearings designed to minimize drag and maximize lifespan.

However, on many modern road frames, derailleur cables (especially for mechanical groupsets) are routed internally and often pass through a guide beneath the bottom bracket shell. These cable guides can wear out or trap dirt, leading to increased friction and compromised performance.

Replacing these cables—especially the front derailleur cable—often requires partially or fully removing the crankset and inspecting the area under the bottom bracket, particularly on frames using bottom bracket cable guides.

Tools Required

  • 5 mm Allen wrench [paid link]
  • Hollowtech II crank arm tool (TL-FC16 [paid link] or compatible)
  • Bottom bracket tool [paid link] (TL-FC32 [paid link] or compatible)
  • Internal cable routing tool or magnet guide
  • New shift cable and housing
  • Torque wrench [paid link]
  • Grease
  • Cleaning rags
  • Cable cutter
  • Frame-specific BB cable guide (if replacement is needed)

Removing the Crankset for Access

To begin cable replacement on frames with cables routed under or near the bottom bracket shell, you must first remove the crankset:

  1. Loosen the pinch bolts on the non-drive side crank arm using a 5 mm Allen wrench [paid link].
  2. Remove the crank arm cap with the Hollowtech II crank arm tool.
  3. Gently pull the non-drive crank arm off the spindle.
  4. Slide the drive-side crank arm and spindle out of the bottom bracket.

At this stage, inspect the SM-BB93 bearings for wear, grit, or resistance. Clean the external cups with a dry cloth and inspect for water ingress or corrosion. Any issues here may require removing the bottom bracket entirely and servicing or replacing it.

Inspecting and Replacing the Cable Guide and Cable

With the crankset removed, the bottom bracket shell area is now accessible:

  • Inspect the plastic cable guide under the BB shell. If it’s cracked, loose, or excessively dirty, replace it.
  • Check the routing path for sharp bends or worn housing ends that can increase friction.

To replace the front derailleur cable:

  1. Unclamp the old cable from the derailleur.
  2. Pull the old cable out completely through the shifter end.
  3. Insert a new cable using an internal routing tool or magnet guide to ensure a smooth path.
  4. Feed the new cable through the housing and bottom bracket cable guide.

Avoid using excessive force. Smooth movement through the guide is critical to avoid damaging the housing or compromising shifting quality.

Reinstalling the Crankset and Final Adjustment

After the cable is correctly routed:

  • Grease the crank spindle and bearing contact surfaces.
  • Insert the drive-side crankset through the SM-BB93.
  • Reattach the non-drive crank arm and torque the pinch bolts to 12–14 Nm.
  • Adjust the preload cap using the Hollowtech II tool to remove any side play, then secure the pinch bolts again.

Finish the installation by tensioning the derailleur cable, setting the limit screws, and indexing the gears.

Performance Optimization Tips

  • Always replace the housing along with the cable if friction was present during shifting.
  • Lubricate the new cable with a light grease or cable-specific lube before insertion.
  • Keep the area around the SM-BB93 dry and clean—dirt ingress can shorten the life of the bearings.
  • Avoid overtightening the cable clamp bolt on the front derailleur to prevent cable fraying.

When to Replace the SM-BB93 Instead

If you hear grinding or feel resistance in the bearings after removing the crankset, it may be time to replace the SM-BB93 entirely. Over time, water, grit, and corrosion can degrade bearing performance, even in high-end models. Use a proper bottom bracket tool [paid link] to remove and reinstall a new unit, following torque specifications and applying anti-seize to the threads.

FAQs

1. Does the SM-BB93 bottom bracket itself use a cable?
No, it does not. However, the front derailleur cable may be routed through or beneath the bottom bracket shell, affecting performance.

2. Can I replace the cable without removing the crankset?
On some frames with external cable routing, yes. For internal or under-BB routing, crankset removal is often necessary.

3. What should I use to lubricate the new cable?
A light Teflon-based grease or cable-specific lube reduces friction and prevents corrosion.

4. How do I know if my cable guide needs replacing?
Check for cracks, excessive wear, or if the cable housing is misaligned. Any of these warrant replacement.

5. Will changing the cable affect my bottom bracket?
Indirectly, yes. Poor cable routing can lead to dirt accumulation around the BB shell, affecting longevity.

6. Should I use stainless steel or coated cables?
Coated cables offer lower friction but may peel over time. Stainless steel is more durable and corrosion-resistant.

Conclusion

Replacing the cable near the SM-BB93 bottom bracket isn’t just about routing a new line—it’s about maintaining the performance integrity of your entire drivetrain system. While the SM-BB93 doesn’t involve direct cable engagement, understanding how your front derailleur cable passes near or through this critical junction can prevent friction, improve shifting precision, and extend the lifespan of both the bottom bracket and your cabling system. Always take the time to inspect surrounding components when performing this task to ensure a complete and optimized result.