Sometimes when installing a new bike chain, bike shops over-estimate the chain length. Other times when you purchase a chain to install yourself, the chain is much too long and must be sized to fit correctly. More commonly, though, our bike chains have stretched from wear and it’s time for a new one. No matter the specific situation it is important to know how to check for proper road bike chain length.
So… how do you check to see if your road bike chain is too long? There are multiple methods for checking proper bicycle chain length. These methods include comparing a correctly fitted old chain with a longer new chain, the Z method, the largest cog/largest chain ring method, measuring worn chain length, and lifting stretched chain from the chain ring.
The correct sized bike chain will be able to accommodate all the possible gear combinations while still maintaining the proper amount of slack tension with the use of the bicycle’s rear derailleur. If one’s chain is too long, then a rider won’t be able to keep it tight enough, it will be too slack to shift gears and or perform properly in general. If one’s chain is too short, then a rider won’t be able to shift onto the large-large combination (or by doing so will break the chain in half.)
Two Types of Multi-Speed Bike Chains
In determining the correct chain size, it’s helpful to note which type of multi-speed bicycle chain you have on your bike currently or are looking to purchase (as the methods below will reference one or the other).
Master Link Chains
Master link chains use two removable outer plates to connect the chain. If a master link chain is what you have, then you’d want to use master link pliers (like Park MLP-1.2 pliers) to disengage the master link. If you don’t have master link specific pliers, you can technically use needle-nosed pliers. However, it will be a difficult process and will take much longer to disengage the link. It is especially futile to attempt to remove the master link with only your hands, so best not even try that.
If your chain is worn out, then there is no need to strategically remove the master link. You’ll want to cut the chain to remove it at this point, and you can do this using a Chain Tool (specifically made for cutting chains.)
Connection Rivet Chains
Connecting rivet chains use a specific rivet (or pin) to connect the chain together. The connecting rivets on this type of chain will have a noticeably different appearance from the other rivets. When you select a rivet to break, make sure that it is at least 2-3 links away from any connecting rivets that are already present in the chain.
When you use the chain tool, the driving pin will make contact with the connecting rivet. At this point, make sure that it looks like the pin is driving a straight line into the chain rivet (so that it’s a smooth exit.) Turn the handle of the chain tool with gusto and push the rivet out. The chain will disconnect then, and you can remove the chain from the bike.
Methods to Determine if Chain is Correct Length
If you are on your bike and it feels like there is some sagging or slapping around sensations occurring near the chain, it is likely your chain is either stretched/warn and no longer fits, or your newly installed chain is just too long. There are multiple ways to check to see if your road bike chain is sagging (too long). The sensible way to do so is not while riding your bike (because that’s unsafe) but rather to stop your bike and check while immobile, or better yet to wait to check properly until at home or in a bike shop.
Z Shape Method
One way to check if you do happen to be out on the road is to park the bike and shift into the large-large combination and check for spare chain. To do this, pull a chain link over itself so that it almost makes a z shape. If you can fold a full link over another link, then there’s an extra link in your chain making it a little too long. If you can keep extending this Z shape with multiple links, then do so until the rear derailleur seems unable to count more links. Doing so will give you an idea of just how many links too long your chain is.
Largest Cog & Largest Chain Ring Method
Begin by shifting the front derailleur over the biggest of the chain rings and the rear derailleur to the smallest possible cog. Then wrap the chain around the large rear cog. Pass the chain end through the front derailleur compartment onto the largest front-most chain ring and hold it at as close to a five o’ clock angle as possible.
If using a mater link chain, install only half of the mater link. Then pull the lower part of the chain snug and connect it to the front chain ring. For accurate sizing, make sure that the chain is fully engaged on the largest rear cog (no weird slack!) You’ll then bypass the rear derailleur initially (and extra length will be retroactively accounted for). Find the nearest rivet where the two chain ends can be joined. Be sure to match the inner plate with the outer plate to make a successful union. Look for the ‘reference’ rivet. This is the rivet closest to where the chain can be joined. From here, add two additional rivets. This section on the two additional rivets is the cutting point for your chain. (If you need further assistance, this video provides adequate visuals and explanations for this process.)
Compare Old Chain with New Chain
If you want to replace your chain, and you know the chain on your bike is the correct size, then you will compare the chains together and cut the new chain at the matching point of the old chain. Always line up the ends with both outer plates and both inner plates. They must match to get the correct length.
How to Know When it’s Time to Replace your Chain
The following methods will help you decide when you’ve got a stretched or worn out chain (while it may not ride like the chain is too long, you will notice a depreciated quality of your ride. When you begin to notice certain parts of your bike have degraded, it’s time to replace the parts, and asap. Unfortunately, worn out parts degrade other parts of the bike. Specifically, a worn-out chain will wear out the chain ring and cassette (both of which are not cheap to replace.)
A bike chain, on the other hand, is cheap to replace, and as it is the part of a bike that wears out most frequently, it’s very crucial to be able to evaluate its health at any given point (so that it doesn’t degrade your bike’s more expensive parts.) Most bike chains will last anywhere from 2,000-3,000 miles depending on the conditions in which you ride, how well you look after your drive train, and how much power you output each ride.
There are two easy methods to discern whether your chain is stretched and needs to be replaced.
Measure the Chain Length
Measuring the length of your bike chain is one easy surefire way to discern how much stretch has occurred in your bicycle chain. To do this, you can either use a Park Tool chain measurer, or a normal ruler. If using a chain measurer tool, pop that tool on top of the chain, allowing the two hooks on either side to sit flat with the chain. If the measuring tool fits at .5, then your chain is still in okay condition. If, however, the chain measurer tool sits at .75 then it is time to replace the chain.
If you don’t have this tool and are using a standard ruler, then you’ll hold the ruler up against the chain length. Eight complete links should equal eight inches, perfectly. If the eight chain links surpass 1/10th over eight inches (i.e., the little line directly proceeding the 8 inches line), then it means the chain has stretched and its time for a new chain.
Pull Away from the Ring
The second more old fashioned way to check the lifespan of your chain is to place the chain in the big chain ring and on the forward-facing part of your bike chain, attempt to lift the chain away from the ring. On a new bike chain, it will hardly lift away from the ring at all (very little give.) However, on an old stretched out chain, the chain will give way more and you’ll be able to lift the chain more easily. If you can do this and can see the chain ring teeth as you lift, it’s time for a new chain.
If you would like to see how it is done, watch here for a more in-depth explanation.
The Key Take Away?
Since bicycle chains are the most frequently replaced part of a bicycle, it is important to learn the signs of wear and stretch and to know when to replace the chain. When it comes to knowing how long the new chain should be, it can be helpful to measure alongside the old chain (as long as the old chain was in fact the proper length.) If your current chain is not worn down, but is a few links too long, you can use various methods (like the Z method or the largest cog/largest gear ring method) to ensure the bike chain length is correct to optimize performance and the ability to switch to all gear combos properly. Now that you are well acquainted with these various methods, hopefully, you can fix your bike chain length at home without needing to take it into the shop!