Experiencing a skippy Shimano CN-6701[paid link] chain is frustrating for any road cyclist, especially when precision and power transfer matter most. Skipping can compromise performance, wear drivetrain components prematurely, and reduce rider confidence. This guide outlines the root causes behind a skippy CN-6701[paid link] chain and how to resolve each issue effectively.
Understanding the CN-6701 Chain: Performance and Design
The Shimano CN-6701 chain is part of the Ultegra 10-speed drivetrain series, designed for high-performance road cycling. It features asymmetrical plate design to optimize shifting and includes a treated surface to reduce friction and extend lifespan. The CN-6701 requires accurate installation and pairing with compatible components to function optimally.
Common Causes of Chain Skipping on the CN-6701
Several mechanical and compatibility factors can lead to chain skipping. Worn drivetrain parts, improper chain length, incorrect installation, and incompatible cassettes or chainrings are primary culprits. Skipping often reveals itself under load, especially during climbs or sprints.
Chain Wear and Stretch: The First Check
A worn CN-6701 chain is a frequent cause of skipping. As chains stretch over time, their pitch no longer matches the teeth on the cassette or chainrings, leading to slippage under torque. Use a chain checker tool to measure elongation. Replacement is advised if wear exceeds 0.75% to prevent damage to other drivetrain components.
Improper Chain Length and Tension
If the chain is too short, it can stress the derailleur and compromise shifting. If too long, it may sag and lead to imprecise engagement. The correct CN-6701 length must be determined using the big-big method (largest front chainring and largest rear cog without the derailleur pulleys overstretched). Ensure proper B-tension adjustment to maintain effective derailleur operation.
Compatibility Issues with Cassettes and Chainrings
Although the CN-6701 is designed for 10-speed Shimano systems, pairing it with non-Shimano or mismatched 10-speed components can result in inconsistent chainline and tooth profile engagement. This mismatch leads to intermittent skipping. Always ensure the cassette and chainrings are fully compatible in both speed and profile.
Rear Derailleur Misalignment or Malfunction
Misaligned derailleur hangers, worn jockey wheels, or incorrect indexing can prevent the CN-6701 chain from staying in gear. Check hanger alignment using a derailleur alignment gauge. Confirm accurate indexing by adjusting barrel tension to align the jockey pulley directly under each cog.
Chainring and Cassette Tooth Wear
Even a new CN-6701 chain can skip if paired with worn cassettes or chainrings. As these components wear, their teeth become shark-fin shaped, reducing proper chain engagement. Inspect tooth profiles carefully and replace any drivetrain parts that show excessive wear to eliminate skipping.
Dirty or Poorly Lubricated Chain
Debris buildup or dry links in the CN-6701 chain can disrupt smooth engagement. Clean the chain thoroughly using a degreaser and apply a quality lubricant. A well-lubricated chain ensures consistent contact with drivetrain teeth and improves performance under load.
Incorrect Chain Installation Direction
The CN-6701 chain has an asymmetrical design and must be installed with the correct side facing out. Reversing the chain compromises shifting and can cause uneven engagement. Look for the model stamping and ensure proper directional installation as per Shimano’s guidelines.
Chain Suck and Chain Drop Considerations
If skipping occurs during front shifting, chain suck or chain drop may be the cause. Chain suck happens when the chain adheres to the chainring and pulls upward rather than releasing. This is often caused by dirty chainrings, excessive wear, or a poorly maintained chain. Check for burrs on the inner chainring and keep the drivetrain clean.
Correct Torque on Chainring Bolts
Loose chainring bolts can allow flexing under load, which causes chain misalignment and skipping. Use a torque wrench[paid link] to ensure chainring bolts are tightened to the manufacturer-recommended specification, typically between 12-16 Nm.
Resolving Indexing and Cable Tension Problems
If the rear derailleur fails to shift accurately across all cogs, the cause might be improper cable tension. Over time, cables stretch, reducing indexing precision. Reset indexing by shifting to the smallest cog, releasing cable tension, and retightening while adjusting the barrel.
Avoiding Cross-Chaining Scenarios
Riding in extreme gear combinations (small chainring to smallest cog or large chainring to largest cog) stresses the drivetrain and promotes skipping. Encourage gear choices that maintain a straighter chainline to reduce friction and enhance drivetrain stability.
Performance Gains After Resolution
Once all mechanical and installation issues are corrected, the CN-6701 chain delivers precise, quiet, and efficient power transfer. Addressing these factors ensures a smoother ride and extends the lifespan of all drivetrain components.
Final Tips to Prevent Future Skipping
Regular inspection, cleaning, and timely replacement of drivetrain components will maintain optimal performance of your Shimano CN-6701 chain. Periodic adjustments and component compatibility checks go a long way in preventing the recurrence of skippy or rough drivetrain behavior.
FAQs
- Can I use the CN-6701 chain with an 11-speed cassette?
No, the CN-6701 is optimized for 10-speed systems and is not compatible with 11-speed cassettes. - What is the maximum chain stretch allowed before replacement?
Replace the chain once it reaches 0.75% elongation to prevent damage to cassettes and chainrings. - Is directional installation mandatory for CN-6701?
Yes, its asymmetric design requires a specific orientation for optimal shifting performance. - How often should I clean the CN-6701 chain?
Clean every 150-200 km or after wet and muddy rides to maintain efficiency. - Why does skipping happen only under high load?
Load exaggerates minor drivetrain misalignments or wear, making skipping more noticeable during climbs or sprints.