Determining The Bike Chain Length Calculator

Do you put on a lot of miles riding your bike each season?

If you are like me, then you probably should be replacing your bike chain every year (that’s right, every year). It’s a simple fact that bike chains wear out and it you want to avoid costly bike repairs, then switching out your bike chain is a very cheap option.

Bike maintenance and repair is a passion of mine. Find out why by reading my “Where It All Began” page.

Bike Repairs – Switching Out Your Old Chain

Performing a chain replacement on your bike is really quite an easy task to do. I use the article “Diagnose Chain Length for Derailleurs” as my guide and it hasn’t failed me yet.

It gives you 2 steps to determining proper chain length, but it does assume though that your old chain has been removed.

To discover how to remove your old bike chain, read the article “How to Clean and replace a Bike Chain”. It shows you how to get that old chain off for good or to so that you can get it properly cleaned (another very important piece of bike maintenance).

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Ways to Determine Your Optimum Bike Chain Length (Steps)

1 – Use Your Large Chain Ring and Largest Rear Cog

The first thing you will need to do is to calculate (by measuring), the longest length of chain that you will need for your bike’s derailleur setup. To do this, thread your new chain length onto your largest front chain ring and also onto your largest rear cog without threading it through your rear derailleurs.

Bring the end of the chain around and hold it against the side of the rest of the chain to find the approximate chain link that would join it up, leaving only a minor amount of sag. It’s hard to describe this process so see the picture in this article.

Now that you know the proper length you will need to add on 1”. This is quite easy as each link is 0.5” each so you will need to add on 2 links to your measured chain length.

Step 2

Now that you have your chain’s proper length, you need to do this final step to ensure that it is short enough for your current derailleur setup. All you need to do is to thread the chain onto your small ring in the front and onto the smallest cog in the back. The difference with this step (from step 1) is that you are going to thread the chain through the rear pulley’s this time.

With the chain in place, take a look at your rear derailleur; the chain is the proper length when the pulley arms have just enough tension to avoid rubbing between the chain as it snakes its way through the 2 pulley wheels. Take look at the picture in the Park Tool article that illustrates the correct chain length very well. See it here.

New Chain Ready For Testing!

My goal with a lot of these articles is to show you that bike repairs are not always that difficult to perform yourself at home in the shop. By following this article you should now have a pretty good idea of how to properly measure a new chain for proper length.

Any questions on this article or on any other topic just leave a message or comment and I’ll get back to you as quickly as possible.

Thanks and Ride safe!

Robert Flaherty