How to measure chain length on a mountain bike

A bike chain is one of the most important components of a mountain bike. It transfers the power from your pedals to the rear wheel and allows you to shift gears smoothly. However, a bike chain can wear out over time and need replacement. A worn-out chain can cause poor shifting, chain skipping, or even damage your drivetrain. When you replace your bike chain, you need to make sure that it is the correct bike chain length for your mountain bike.

A chain that is too long or too short can affect the performance and safety of your bike. But how do you measure a mountain bike chain length? In this post, we will show you three different methods to measure your bike chain length: sizing to the original chain, using the largest cog and chainring, and how to calculate it.

Method 1: Sizing to the Original Chain

This method is the easiest and most accurate if you have the original bike chain length that was correctly sized for your mountain bike. All you need to do is compare the original chain with the new chain and match the rivets (the pins that hold the links together).

To do this, lay the original chain next to the new chain on a flat surface. Make sure that both chains are fully stretched and aligned. If you have a master link on your chains, insert it on both ends so that your measurement is accurate.

Next, match the rivets on both chains. Slide the rivets on the original chain until they are directly next to the rivets on the new chain. You may notice that the original chain is slightly longer than the new chain because it has stretched over time.

Finally, mark where you need to cut the new chain. The rivet on the new chain that matches the end of the original bike chain length is where you need to cut. You can use a marker or a tape to mark it. Then, use a chain tool or a master link to cut and join the new chain.

Method 2: Using the Largest Cog and Chainring

This method is useful if you don’t have the original bike chain length or if it was not correctly sized for your mountain bike. You will need to wrap the new chain around the largest cog in the rear and the largest chainring in the front, without routing it through the rear derailleur.

To do this, shift your front derailleur to the largest chainring and your rear derailleur to the smallest cog. Then, drape the new chain around the largest cog in the back and pull it onto the largest chainring in the front. Make sure that the chain is fully engaged on both sprockets.

Next, pull the chain tight and bring both ends together until they touch. Then, add two more links (one inner and one outer) to this length and mark where you need to cut. This will give you enough slack to shift smoothly and avoid damaging your derailleur.

Finally, use a chain tool or a master link to cut and join the new chain.

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Method 3: Bike chain length Calculator

This method is based on a mathematical formula that takes into account your sprocket sizes and your chainstay length (the distance between your bottom bracket and your rear axle). You will need to measure these values with a ruler or a tape measure and plug them into this equation:

L = 2 © + (F/4 + R/4 + 1)

Where:

• L = Bike chain length in inches (rounded up to the nearest inch)
• C = Chainstay length in inches (measured to the closest 1/8 inch and converted to decimal form)
• F = Number of teeth on your largest front chainring
• R = Number of teeth on your largest rear cog

For example, if your mountain bike has a 32-tooth front chainring, a 50-tooth rear cog, and a 16.5-inch chainstay, then your bike chain length should be:

L = 2 (16.5) + (32/4 + 50/4 + 1) L = 33 + (8 + 12.5 + 1) L = 33 + 21.5 L = 54.5

Round this number up to 55 inches and cut your new chain accordingly.

Conclusion

Measuring bike chain length on a mountain bike is not a difficult task, but it is an important one. A properly sized chain will ensure optimal performance, durability, and safety of your bike. You can use any of these three methods to measure your bike chain length, depending on your preference and availability of tools.

Remember to always use a compatible chain for your drivetrain system and follow the manufacturer’s instructions for installation and maintenance. If you are unsure about how to measure or adjust your bike chain length, you can always consult a professional bike mechanic for assistance.

We hope this post has helped you learn how to measure bike chain length on a mountain bike. Happy riding!