Crashing is part of cycling as crying is part of love.
Johan Museeuw
- The Lion of Flanders
Replacement chains for bicycles are typically longer than needed. This guide will walk you through various methods for properly sizing your bike chain, highlighting essential tools, steps, and common mistakes to avoid.
How to Size the Chain Length of MTB?
Step 1: Preparation:
Tools and Preparation
Before beginning the chain sizing process, gather the necessary tools:
- Chain tool or chain pliers
- Master link (if applicable)
- Measuring tape or ruler
- Bike stand (optional)
Inspect and Remove the Chain
- Verify the Old Chain’s Length:
- Shift the bike to the largest chainring and largest rear cog. The chain should make this shift with slight bends at each pulley of the rear derailleur.
- Shift to the smallest chainring and sprocket. There should be no slack in the chain, and the derailleur should not pull so far back that the chain contacts itself.
- Remove the Chain
- Remove the rear wheel to release tension from the chain and get better access
- Look for a master link. If present, use master link pliers to disengage it. If your chain is worn out, you can cut the chain using a chain tool, ignoring the master link
Handling Connecting Rivet Chains
- Identify and Remove the Connecting Rivet:
- These rivets look different from the others. When removing a chain, select a rivet a few links away from any connecting rivet to avoid weakening the chain.
Step 2: Sizing your mountain bike chain
Option 1: Match with the Original Chain
- Align with the Old Chain
- Lay the old chain next to the new one, matching outer plates with outer plates or inner plates with inner plates.
- Insert the master link if applicable for a true side-by-side comparison. Align the chains rivet by rivet, noting that old chains stretch over time
Option 2: Sizing for Large Rear Cogs (42 teeth and up)
- Route the Chain:
- For dedicated 1X systems with extra-wide rear cogs (42 teeth or larger), route the chain over the front ring and the largest rear sprocket without passing through the derailleur.
- Measure and Cut:
- Identify the shortest length where a chain would connect inner and outer plates. Count four additional rivets (two inches) from this point to determine the position to shorten the chain.
Option 3: Largest Cog and Chainring Method (36 teeth or lower)
- Prepare for Measurement:
- Shift the front derailleur to the largest chainring and the rear derailleur to the smallest cog to move the derailleur out of the way.
- Wrap the Chain Around the Largest Gears:
- Wrap the chain around the largest rear cog and the largest front chainring, bypassing the derailleur.
- Determine the Cutting Point:
- Pull the lower section of the chain snug. Identify the closest rivet where the chain ends can be joined, then add two additional rivets to find the cutting point.
- If the lower section meets an outer plate, add one rivet and then two more before cutting.
Additional Considerations and Exceptions
Chain Guides:
- Ensure the chain is routed through any chain guide before determining its length.
Rear Suspension:
- Disconnect the shock and compress the linkage to its bottom position to account for changes in distance between the rear cogs and front chainrings as the suspension moves.
Full-Suspension Bikes:
- With the suspension fully compressed, check the chain length again. Ensure there is no excessive tension that could damage the derailleur or drivetrain.
Special Drivetrains:
- Some bikes with unique drivetrain setups (like internally geared hubs or belt drives) might require special consideration. Always refer to the manufacturer’s guidelines.
Tips and Bonus Information
- Double-Check Measurements: Always double-check your measurements before cutting the chain to avoid mistakes.
- Proper Lubrication: Use the right amount of lubricant for your riding conditions. Over- or under-lubrication can cause premature wear.
- Invest in Quality Tools: Good tools make the process easier and more precise.
Common Mistakes and Solutions
Overtightening the Chain:
- Avoid making the chain too tight, which strains the drivetrain. Ensure there’s a small amount of slack.
Incorrect Routing:
- Pay close attention to the chain’s path through the derailleur to prevent poor shifting and chain drops.
Not Accounting for Stretch:
- Chains stretch over time. Don’t rely solely on the old chain’s length. Always verify using the big-big method or measurement tools.
Never Cut the Wrong Chain Again
Sizing a mountain bike chain correctly is crucial for ensuring smooth and efficient rides. Following the right steps, using the appropriate tools, and understanding the nuances of your specific drivetrain can save you from common pitfalls and frustrations. If you want to enhance your MTB chain maintenance skills, check out our comprehensive guide on MTB chain routing.
We’ve covered everything from the initial tools and preparation to detailed methods for different types of drivetrains, along with essential tips and considerations.
Have you had any challenging experiences when sizing your bike chain? Did you ever cut the chain to the perfect length only to realize it was the wrong chain speed?
Share your worst case experiences and tips in the comments below. Let’s learn from each other and keep our bikes running smoothly!
