The Shimano SM-BB5700 [paid link] Hollowtech II bottom bracket is a robust component designed to support high-performance road cycling. While limit screws are typically associated with derailleurs, this model’s setup involves preload adjustment that often gets misunderstood as limit screw calibration. In practice, achieving optimal bearing preload and correct crank arm installation is the critical step for proper function, longevity, and noise prevention. Misadjustment can lead to excessive bearing wear, lateral play, or creaking—all symptoms of incorrect assembly or preload.
This guide breaks down the nuanced process of correctly setting up the Shimano SM-BB5700 [paid link]’s preload system, often confused with limit screw adjustments, and clarifies every detail needed for smooth and durable operation.
Understanding the Preload Adjustment System on SM-BB5700
Unlike traditional limit screws found on derailleurs, the SM-BB5700 uses a crank arm preload cap and pinch bolts to adjust the bearing load and secure the crank in place. These components functionally serve as the “limit system” for bottom bracket alignment and axle float prevention.
The preload cap, threaded into the left crank arm, applies light axial pressure onto the crank spindle. This eliminates lateral movement between the crank and the bottom bracket, which mimics the effect of a limit adjustment by restricting crankset travel.
The pinch bolts on the left crank arm then clamp the arm onto the spindle to fix it in place after preload has been set.
Common Issues Linked to Improper Preload Adjustment
Misinterpreting the preload cap’s role or failing to correctly tighten the pinch bolts can cause several issues:
- Creaking under load: Caused by insufficient preload or poorly torqued pinch bolts.
- Axial crank movement: Indicates the preload cap wasn’t adequately tightened before securing the crank arm.
- Excessive bearing drag: Over-tightening the preload cap compresses the bearings beyond spec, leading to rapid wear and friction.
- Crank arm separation: A loose or untorqued pinch bolt setup can lead to serious drivetrain failure.
These symptoms mirror the kinds of problems limit screws help control in other components, reinforcing the importance of correct preload adjustment in this context.
Preload Adjustment Procedure for SM-BB5700
Correct preload and clamping sequence ensure optimal function. Here’s how to fine-tune the setup:
Step 1: Prepare the Crankset
Before installation, ensure all components are clean and properly greased:
- Apply a thin layer of waterproof grease on the crank spindle.
- Ensure both bottom bracket cups are fully seated in the frame and torqued to specification (35–50 Nm).
Step 2: Insert the Right Crank Arm
Slide the right crank arm with spindle through the bottom bracket from the drive side. The spindle should pass smoothly with no binding.
Step 3: Install the Left Crank Arm
Attach the left crank arm by aligning the crank arms at 180 degrees opposite each other. Lightly thread the preload cap into the left crank arm by hand until it contacts the spindle.
Step 4: Set the Preload
Using the Shimano TL-FC16 [paid link] or a similar compatible preload tool, rotate the preload cap clockwise until it’s snug—not tight. Shimano recommends finger-tight only, typically <0.7 Nm. The goal is to eliminate side-to-side play without adding bearing load.
Do not use pliers or overtighten. This cap is not a clamping mechanism—it’s strictly for adjustment.
Step 5: Secure with Pinch Bolts
With preload properly set, torque each pinch bolt in sequence to 12–14 Nm, alternating between them to apply even pressure. This secures the crank arm and locks in the bearing preload.
Recheck preload after tightening. If crank movement is detected, loosen the bolts, readjust the cap, and repeat.
Fine-Tuning for Smooth Rotation
Once installed, spin the crankset. It should rotate freely but not feel loose. If there’s stiffness, back off the preload slightly. If lateral movement exists, reapply preload before re-securing the arm.
The Shimano SM-BB5700’s performance depends on precise preload, making this step functionally equivalent to adjusting a limit screw to avoid under- or over-extension.
Signs You Need to Recheck Adjustment
Reinspect the bottom bracket system if you notice:
- Gradual increase in pedaling resistance
- Clicking or creaking with each pedal stroke
- Lateral crank movement when side-loaded
- Audible grinding or bearing noise
Such symptoms often point to a shift in preload or loosening of pinch bolts, especially if ridden hard or installed improperly.
Maintenance Recommendations
To preserve correct preload and prevent recurring adjustment:
- Check crank preload every 1,000–1,500 km.
- Retorque pinch bolts after initial break-in (~100 km).
- Inspect for contamination or moisture ingress during cleaning sessions.
- Re-grease and recheck preload after any crankset removal.
Maintaining this balance ensures that your Shimano SM-BB5700 performs silently and smoothly for thousands of kilometers.
Conclusion
Though the Shimano SM-BB5700 doesn’t feature literal limit screws, its preload system acts similarly by defining the mechanical constraints of crank movement. Correct adjustment of the preload cap and securement with pinch bolts is essential for optimal performance. Riders must treat this step with precision and care to prevent drivetrain damage and maximize longevity.
For best results, always use the recommended Shimano tools and follow the torque values strictly.