The Shimano CN-HG93 [paid link] chain is a trusted choice among road cyclists and mountain bikers alike, known for its smooth performance and high durability. However, achieving optimal drivetrain efficiency requires one crucial step that is often overlooked: setting the correct chain length. Misjudging chain length can compromise shifting performance, cause drivetrain noise, and accelerate component wear. In this guide, we’ll walk you through everything you need to know about correctly adjusting the length of your CN-HG93 [paid link] chain.
Understanding the Importance of Proper Chain Length
The length of the chain impacts shifting performance, pedaling efficiency, and overall drivetrain longevity. A chain that is too long will sag, resulting in sloppy shifting and poor chain tension. Conversely, a chain that is too short can damage the rear derailleur or cause an inability to shift into the largest cogs or chainrings. For the Shimano CN-HG93 [paid link], which is a 9-speed chain, precision is particularly important because 9-speed systems require exact indexing to function properly.
Proper chain length ensures that the derailleur maintains the correct chain wrap around the cassette and chainrings. It also ensures the derailleur can maintain adequate tension across all gear combinations without overstretching.
Tools Required
- Chain tool (chain breaker)
- Chain wear checker
- Quick link pliers (if using a master link)
- Shimano CN-HG93 chain
- Derailleur hanger alignment tool (optional but recommended)
Initial Chain Length Measurement
The most reliable method for determining the correct chain length for the CN-HG93 is the “big-big” method—looping the chain around the largest front chainring and the largest cassette sprocket without routing it through the rear derailleur.
- Thread the chain over the largest front chainring.
- Loop it around the largest cassette cog.
- Pull the two ends together until they meet.
- Add two full links (one inner and one outer link) to this length.
This method ensures the rear derailleur has enough capacity to handle the chain in the most extreme gear combinations.
Important Tip: Always perform this measurement on a new, unworn chainring and cassette for the most accurate result. Worn components may require additional adjustments later on.
Using the Derailleur Capacity as a Check
Shimano specifies derailleur capacity, which can be used to double-check your chain length setup. For a 9-speed drivetrain using the CN-HG93, check the total drivetrain capacity (front difference + rear difference) and ensure the rear derailleur can accommodate it.
If your drivetrain has wide gear range (such as compact or triple cranksets), ensuring your rear derailleur can handle the capacity is critical to proper chain sizing. For example, if the largest chainring is 50T and the smallest is 34T (16T difference), and the cassette ranges from 11T to 32T (21T difference), the total capacity needed is 37T.
Always cross-reference your component specs to avoid unexpected compatibility issues.
Cutting the Chain to Size
Once you have determined the correct chain length, it’s time to cut the CN-HG93 chain:
- Using a chain tool, drive the pin out at the appropriate link.
- Avoid cutting at the quick link area if you’re using Shimano’s special connecting pin; position the cut so you have an outer link on one side and an inner link on the other.
If you are using a quick link to connect the chain, ensure that both ends are inner links to accept the master link.
Note: Shimano recommends using their connecting pin for the CN-HG93, although third-party quick links designed for 9-speed chains are also widely used by mechanics for easier installation and removal.
Installation and Initial Setup
- Route the shortened chain through the front derailleur cage.
- Feed it through the jockey wheels of the rear derailleur, ensuring correct routing through the derailleur cage plates and the tension pulley.
- Connect the chain using the Shimano connecting pin or master link.
Shift the bike through all gears to confirm proper chain tension and derailleur operation. Pay special attention to shifting performance in the large-large and small-small gear combinations.
Common Mistakes and How to Avoid Them
Skipping Big-Big Method
Some mechanics use the small-small method or make educated guesses based on old chains. Avoid these shortcuts as they can result in mis-sizing.
Ignoring Derailleur Angle
After chain installation, the derailleur cage should angle slightly backward in the largest cog/largest chainring combination. A fully extended derailleur cage indicates a chain that is too short.
Not Accounting for Suspension Compression
For full-suspension bikes, ensure that the chain length accounts for the furthest distance between the bottom bracket and the rear axle when the suspension is fully compressed.
Incorrect Master Link Use
Using a quick link that’s incompatible with the CN-HG93 (9-speed) can cause premature wear or breakage. Always verify that the link matches your chain’s speed rating.
Verifying Chain Length After Installation
Shift the bike into the smallest chainring and the smallest cog. The rear derailleur should not be fully slack; there should be slight tension keeping the chain taut. In the largest chainring and largest cog, the derailleur should not be overstretched.
Rotate the cranks and observe the derailleur motion. If the chainline is smooth and the derailleur shifts without struggle across the range, the chain length is correctly set.
When to Recheck Chain Length
Chain stretch over time can affect drivetrain performance. Using a chain wear checker periodically can alert you to elongation. Once a chain shows 0.75% elongation, it’s time to replace it to preserve cassette and chainring lifespan. However, if replacing other drivetrain components or altering gear range, it’s essential to reassess chain length from scratch.
Conclusion
Proper chain length adjustment on the Shimano CN-HG93 is essential for achieving smooth, efficient, and reliable drivetrain performance. Following precise measurement methods, avoiding common pitfalls, and verifying the final setup ensures the CN-HG93 delivers its intended performance characteristics. Taking the time to get the chain length right pays off in the form of crisp shifts, quieter rides, and longer component life.