How Can I Tell if My Bike Chain is Wearing Out?

Other than tires (and tubes), chains are one of the parts of your bike prone to wear out most often—especially if you ride hard and ride a lot. Your chain is under a lot of stress when you hit the trail. If you think about it, all of the force your legs generate propelling you along the trail is getting transferred to the chain. So, maintaining and changing your chain as needed will not only make for a better ride, but will save extra wear and tear on your drivetrain.

It’s About Spacing

Take a look at your chain and you’ll notice that there are two main parts—the inner link and the outer link. There’s more to a bike chain’s construction, but we’re going to keep it simple here. Each chain link is connected to the next with pins, alternating between inner links and outer links.

It should be obvious that the spacing between the links is uniform all the way up and down the length of the chain. This gap between the links is where the teeth of your bike’s gears grab onto the chain and propel you forward. The spacing between the pins should be 0.5in (12.7mm), which is the industry standard for chains used on multi-speed bikes that use a standard derailleur.

Not sure what some of the terms in this article mean? Check out the NTX Trails Glossary of MTB Terms and Slang.

Identifying Chain Wear

As you ride your bike and put stress on the chain, over time the chain begins to stretch out—this is called, obviously enough, chain stretch. This happens because the metal bushings on the links wear the pins down. As the pins wear down, the spacing between the links increases, which produces slow and inconsistent shifting. If you’re beginning to experience this sort of shifting trouble, there are a couple of methods you can use to determine if you need a new chain.

First, you can measure your chain using a ruler. A new chain will measure exactly 12 inches across 12 links, from the middle of the first pin to the middle of the last pin. A one-percent stretching of your chain is considered worn and worthy of replacement. If you’re wondering, or simply don’t want to work out the math, that means anything longer than 12 1/16 inches means you need a new chain.

A second, and far more accurate method for measuring your chain is to use a chain checker. There’s some debate on the accuracy of these tools since some models push the rollers in opposite direction when used. Other makes are designed in such a way that the rollers are pushed in the same direction, therefore (theoretically) offering a more accurate reading. Our advice is to do your own research before you buy a chain checker.

Is the Chain Sloppy?

Another type of wear that’s much harder to identify is called slop. This is caused by the amount of torque a rider places on the chain—typically while climbing or attempting to shift gears under load. Slop is side-to-side chain wear that cannot be identified by measuring chain length. The symptoms of slop are the same as chain stretch: slow shifting and shifting inconsistencies.

So, how do you tell if your shifting troubles are caused by chain slop? If you’re having shifting difficulties, check first to see if your chain is stretched. Next, see if minor adjustments to your shifters or derailleurs help. If neither issue seems to be the culprit, you have two choices—either bite the bullet and spring for a new chain, or take your bike to the shop and see what the mechanics think. Either way, you’re going to be out some cash, so it seems to us that the less expensive option is to go ahead and buy a new chain.

In the end, deciding whether or not you need to replace your chain isn’t that difficult. Don’t overthink it. If you legitimately suspect your chain is worn then buy a new chain. You’ll be happy you did in the long run because using a severely worn chain can cause irreparable damage to your cranks, cassette, and derailleur pulleys—all of which are much more expensive to replace than your chain!

For a more in-depth look, check out this great video from Park Tool.