SM-BB6700 Limit Screw Adjustments: How to Get Them Just Right

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The Shimano SM-BB6700 [paid link] bottom bracket is a key component in the Ultegra 6700 series, designed for road cyclists seeking precision, stiffness, and longevity. As a threaded bottom bracket designed for Hollowtech II cranksets, its performance depends heavily on accurate installation and precise adjustment. Although bottom brackets do not have traditional “limit screws” like derailleurs, fine-tuning crankset bearing preload and spindle alignment plays a similar role in achieving optimal performance. In this guide, we’ll walk through how to accurately adjust the SM-BB6700 [paid link] and achieve the equivalent of “limit screw perfection” by focusing on bearing preload and crank arm fit.

Understanding the SM-BB6700 Structure

The SM-BB6700 [paid link] is a Hollowtech II bottom bracket designed to fit threaded English (BSA) bottom bracket shells. Its core structure includes:

  • Left and right threaded cups with integrated bearings
  • Plastic inner sleeve for water and debris protection
  • Use of external bearing placement for improved stiffness

Despite its simple appearance, improper adjustment during installation can result in creaking, premature wear, or poor crank rotation—all issues cyclists often mistake for drivetrain problems.

What Are “Limit Screws” in the Context of the SM-BB6700?

Limit screws traditionally refer to mechanical stops used in derailleurs. For a bottom bracket like the SM-BB6700, there are no physical screws to limit motion. However, the bearing preload cap on the left crank arm and fixing bolts that secure the crank to the spindle function similarly. They control how much lateral pressure is applied to the crank bearings, affecting crank alignment, drag, and wear.

Thus, the term “limit screw adjustment” in this context means fine-tuning these preload mechanisms.

Tools Required

  • 5 mm Allen key
  • Shimano Hollowtech II crank arm preload cap tool (TL-FC16 [paid link] or TL-FC18)
  • Torque wrench [paid link] (5–10 Nm range)
  • Grease (suitable for steel or aluminum threads)
  • Clean rag or paper towels

Step-by-Step Bearing Preload Adjustment Process

1. Ensure Correct Bottom Bracket Installation

Before adjusting preload, confirm that the SM-BB6700 is correctly installed:

  • Shell Prep: The frame’s bottom bracket shell must be faced and chased. Thread cleanliness and smoothness are essential.
  • Cup Installation: Grease threads and install the right cup (drive side) clockwise, left cup counterclockwise to 35–50 Nm torque.
  • Sleeve Positioning: Ensure the plastic sleeve is correctly seated to prevent water ingress.

Only after this foundation is secure should you proceed with crank installation and preload adjustments.

2. Install the Crankset Without Over-Tightening

The Shimano Hollowtech II system uses a two-piece crank. Begin by:

  • Inserting the right crank arm with spindle through the SM-BB6700.
  • Mounting the left crank arm loosely to the spindle splines, ensuring it’s correctly aligned.

At this point, the crankset will feel slightly loose. Do not secure the pinch bolts yet.

3. Adjust the Preload Cap Properly

This is the step most equivalent to setting a “limit screw”:

  • Use the TL-FC16 [paid link] or TL-FC18 tool to tighten the preload cap by hand.
  • Stop turning when resistance is felt—do not overtighten. The goal is zero lateral play in the crank while allowing free spin.

Over-tightening causes bearing drag and premature wear. Under-tightening allows side-to-side crank movement, which can cause noise and misalignment.

4. Torque the Pinch Bolts Sequentially

With the bearing preload set:

  • Tighten the two 5 mm pinch bolts on the left crank arm in an alternating pattern.
  • Use a torque wrench [paid link] to bring each bolt to 12–14 Nm.
  • This sequential tightening ensures uniform clamping and prevents uneven stress on the spindle.

Common Preload Mistakes and Their Fixes

Over-Tight Preload Cap

  • Symptoms: Stiff crank rotation, audible grinding under load.
  • Solution: Loosen cap slightly and recheck crank spin. Bearings should feel smooth and free.

Loose Preload Cap

  • Symptoms: Creaking during pedaling, visible side play in crank arms.
  • Solution: Re-tighten preload cap, then re-secure pinch bolts with correct torque.

Uneven Bolt Torque

  • Symptoms: Misaligned crankset, premature wear on one side.
  • Solution: Use torque wrench [paid link] on both bolts and recheck after 100 km of riding.

Optimizing Preload for Longevity

Achieving just-right preload doesn’t only improve performance—it extends the life of your SM-BB6700. When adjusted correctly:

  • Bearings rotate freely with minimal friction.
  • Water and grime ingress is minimized due to tight fit.
  • Crankset alignment remains consistent, reducing chainline stress.

Regularly recheck preload during routine maintenance. Bearings may bed in after initial rides, slightly loosening the setup. Re-tightening the cap and bolts can restore optimal function.

FAQs About SM-BB6700 “Limit Screw” Adjustments

Q1: Is the preload cap a torque-sensitive component?
No. Shimano recommends hand-tightening only. Use of a torque wrench on the cap is discouraged.

Q2: How often should I re-check the preload adjustment?
After initial 100–200 km, then every 1,000 km or during scheduled drivetrain service.

Q3: What happens if I skip preload adjustment?
Incorrect preload leads to crank wobble, excessive drag, or early bearing failure.

Q4: Can I use aftermarket preload caps?
Yes, but ensure compatibility and avoid metal caps that can easily be over-tightened.

Q5: How do I know if I got it “just right”?
The crank should spin smoothly without lateral play. No resistance or noise when rotating by hand.

Q6: Is there a difference in preload process for carbon frames?
No, but ensure frame inserts are not damaged and preload does not cause creaking at the shell.

Conclusion

While the SM-BB6700 doesn’t include traditional limit screws, fine-tuning its preload cap and crank arm bolts plays an equivalent role in performance and longevity. By understanding and adjusting these components precisely, you can ensure a smooth, durable, and creak-free riding experience. Missteps in this process often masquerade as drivetrain or crank issues, so proper adjustment is not only preventative but performance-enhancing. Make it a regular part of your maintenance routine to keep your bottom bracket—and your ride—running flawlessly.