Chains are a consumable part of the bicycle’s drivetrain. As you pile on the miles, your bike’s chain will wear out. The internal parts of the chain, the rollers and rivets, begin to wear down and give the illusion of stretching. This wear can cause the chain to mesh poorly with the cogs and chainrings, causing poor shifting, premature wear to the cogs, and even skipping over the cogs. And since it’s far more expensive
to replace cogs than a chain, you can actually save money
by learning when it’s time to replace the chain. Hi I’m Ben with Park Tool.
There are different methods for measuring chain wear from simply lifting the chain off the front chainrings, to measuring the distance between two rivets on a chain but the easiest and most accurate way to determine the amount of life left in your chain is with a tool like the CC-3.2 Wear Indicator,
or the CC-2 Chain Checker. we’ll put the bike in a repair stand,
but all of this can be done on the ground as well The first method to check chain wear is to simply try and lift the chain off the front chainring. Shift to the smallest cog in the rear and the large chainring in front and lift the chain. If it lifts off the chainring to where you can see a lot of daylight between the chain and chainrings, you either need to replace your chain
or you’re getting pretty close. It’s not nearly as accurate as using the proper tool, but it’s a good starting point if you haven’t replaced your chain in a little while. Another ballpark method for checking chain wear
is by measuring it with a ruler. This is a new chain, and each rivet is a half inch apart. So if we line up the first rivet at zero, we should see our 24th rivet at the 12 inch mark. On the bike, we do the same thing, and if we end up short on our
24th pin by more than 1/16th of an inch, we should consider replacing the chain. But you can see how difficult and imprecise this method can be. Enter the CC-3.2 and the CC-2. Let’s look at the CC-3.2 first. Note which side of the tool has the 0.5 stamp. Install the hook end on a link with inner plates to ensure you are measuring against the roller, not the side plates. Attempt to install the other end into the chain. If it doesn’t go in, your chain is not yet .5% worn. This chain is brand new, so this makes sense. On this other chain, it does go in,
which tells us the chain is at least .5% worn. in other words, it’s .5% longer than it was when it was new. We switch to the other side of the tool to check for .75% wear. If it does not insert all the way, we know the chain is not yet worn to the .75% level. and this older chain is worn well beyond the .75% mark, and at this point the cogs may also be worn. Let’s talk about what each reading means. Anything at or beyond .75, you should change your chain immediately. If you are using a chain designed for 10 or fewer gears, replace your chain as it reaches .75% wear. If you are using a 11- or 12-speed chain, replace your chain once it has reached .5% wear. And for two sprocket or single speed bikes, replace your chain when it has reached 1 percent wear. Now let’s check using the CC-2. Insert the rear stud between two outter plates, and the front stud between inner plates. Push lightly on the lever to take slack out of the chain, and feel where it comes to a distinct stop. Don’t force the tool beyond the stopping point. The reading in the window will give you the percent wear of your chain. This is the same chain that was worn beyond the .5% mark, but hadn’t reached .75% wear so this reading makes sense. And because this bike has an 11 speed cog set, we’ll replace it because it’s recomended at .5% wear. So that’s how to know when it’s time to replace your chain. Remember, using a chain beyond it’s intended wear limit will prematurely wear out your cogs and chainrings, so staying on top of this routine maintenance task can really save you some hassle in the long run. Thanks for watching this video on chain wear. If you have any other quesitons about how to replace your chain, watch these other videos from Park Tool.