Is My Mountain Bike Chain Too Long? Symptoms & Fixes
The mountain bike chain is one of the most important components of your bike. It is the part that enables your bike’s wheels to move whenever you push on the pedals with sufficient energy and needs to be fixed firmly around the sprocket. Chains that are too tight make riding difficult and stressful. When the chains are too long or loose, they could slip off the sprocket and possibly cause harm to you. But how will you know if your mountain bike chain is too long?
A mountain bike chain is too long if it causes dropped chains, poor shifting, and sagging. Dropped chains refer to the falling of the chains off the chainrings, making it impossible to pedal. To find the right length for a mountain bike chain, use the formula L = 2 x C + F / 4 + R / 4 + 1, where L is the length of the chain in inches, C is the length of the chainstay in inches, F is the number of teeth on the largest front chain ring, and R is the number of teeth on the largest rear cog.
Though this simple equation is mostly used to calculate the length of straightforward and uncomplicated chains, there is yet another more complex equation, the rigorous equation which is used to find the length of relatively complex chains with small dimensional chainstays.
Symptoms Of A Bike Chain That’s Too Long
A loose mountain bike chain exhibits a wide variety of symptoms. Some of these symptoms can be seen with the naked eye while other symptoms may be noticed while riding.
A bike chain that’s too long or loose may drop off the gear, make a clunky sound, have inconsistent front and back shifting, or sag.
Should you feel that your mountain bike is needing more and more maintenance and is nearing the end of its useful lifespan for you, have a look at our article that explores what mountain bike you should buy to help you choose a suitable upgrade like this.
You might also find interest in learning how to untangle a mountain bike chain. If so, be sure to read our related article for more information.
Symptom 1. Your Chain Dropps off the Gear
A loose chain will occasionally drop off the gears as you pedal, leading to its rubbing against certain wheel components of your bike like the cog, crankset, and frame. When these rubbing effects occur for an extended period of time, it may lead to the damage of these wheel components of your bike. You might also be interested in learning how to fix a mountain bike chain that's jumping gears. If so, be sure to check out our related article.
Symptom 2. Your Bike Produces a Clunky Sound:
A loose chain is often slack, rubbing freely against other metallic parts of your bike. This rubbing effect produces a rattling and clattering sound which you will often hear during riding.
Symptom 3. You have Inconsistent Front and Rear Shifting.
If your chain is too loose it may skip gears and instead of going to the next gear up or down, it will jump gears making your shifting inconsistent.
Symptom 4. Your Chain Sags
The most obvious symptom of your chain being too loose is that it is sagging and hanging with too much slack.
How To Check If Your Mountain Bike Chain Is Too Long
For a smooth ride, you need to ensure you install the right length chain. Here are very practical steps that can be taken to check and confirm if your bike chain is too long.
To check if the mountain bike chain is too long view the chain as close to eye level as possible to see if the chain is sagging beyond the chain stay or touching the chain stay. Next, check if the derailleur cage moves when the chain shifts during gear changes. Finally, use a chain checker to determine if the chain has lengthened over time.
A very simple method of checking if your chain is too long is by taking a closer, level look at the sides of the chain to observe if there is a sag. A loose chain will often sag close to or below the chainstays as the chain hangs between the rear gears and the chainrings.
You can also check how much the derailleur cage will be moved if the chain is shifted to the big chainring and to the biggest cassette cog. If the derailleur cage moves a little, it means your chain isn’t loose. But if it moves a lot, it’s a big sign that your chain is too long. A long chain affects the shifting of the gears.
A more reliable tool, the chain checker like this can be used to accurately check if the chains are loose. The chain checker has two sides; one side is marked 0.5 while the other has a 0.75 mark. To check if the chain is loose, simply place the chain checker up against the chain. If the chain checker reads 0.5 or 0.75, it means your chain has elongated to 0.5% and 0.75% of its original length. But if it doesn’t get to the 0.5 mark, that means your chain is fine, it hasn’t increased in length.
How To Fix A Mountain Bike Chain That Is Too Loose
If your mountain bike chain is too loose it could be because it is, in fact, too long or that it just needs to be adjusted. You will need a socket wrench to turn the nuts and bolts of your back wheel easily, gloves to protect your hands from dirt, grime, and getting hurt, and a bike stand to position your bike conveniently while fixing it.
To fix a loose mountain bike chain, a socket wrench, gloves, and a bike stand will be needed. Check the chain for sagging, make use of a bike stand to hold the bike up, and loosen the nuts of the rear wheel using a socket wrench.
Check out this informative guide on mountain bike chains from Red Bull.
Here are the various steps involved in fixing a mountain bike chain that is too loose:
Step 1. Check the Chain for Sagging
Closely examine if the chain is low or sagging. You may have to giggle the chain with your hand to be sure that it is loose, and this may require that you wear gloves like these to protect yourself from getting oil all over yourself.
Step 2. Stand the Bike Up Securely
Use a bike stand like this to help keep your bike from falling so that you can perform this task without the bike falling over.
Step 3. Loosen the Nuts of the Rear Wheel
Use a socket wrench like this to loosen both nuts of the rear wheel. But do not completely unscrew the nuts from their positions in order not to separate the rear wheel from the bike. As this may cost you more time and effort reassembling.
Step 4. Reposition the Wheel and the Chain
Holding the end of the wheel with one hand and the bike’s frame with the other hand, pull the wheel back from the frame and reposition the chain. If it was just loose then this should sort the problem out and your chain will no longer be dangling.
Step 5. Tighten the Nuts of the Wheel
When the chain has been properly set in position, tighten the nuts of the wheel using the socket wrench.
How To Fix A Mountain Bike Chain That Is Too Long
If, after following the steps above, the chain on your mountain bike is still too loose then it could be too long.
If a mountain bike chain is too long, use a chain wear tool to see whether it has stretched due to wear and tear and replace it if it has. If the tool doesn’t show stretching, then remove links from the chain.
Step 1. Determine Whether or Not Your Mountain Bike Chain is Stretched
Using a chain wear tool like this measure your mountain bike chain to see whether it has stretched due to wear.
Step 2. Replace the Mountain Bike Chain if it Has Stretched
If the chain is stretched replace it with a new chain as we discuss in our step-by-step guide on how to replace a chain on a mountain bike. Check out this video tutorial from REI that shows exactly how this is done.
Step 3. If the Chain is Not Stretched Remove Links to Shorten it to the Correct Length
By following the instructions in our how-to-guide on mountain bike chain installation you can easily remove links from your chain so that it is the correct length and will keep your mountain bike powering ahead.
Step 4. Do a Test Ride to Check That the Chain is Working Well
Take your bike on a test ride and put it through its paces to check that the chain is working well before you attempt any long rides, in case your chain still has a problem.
Similarly, you're going to want to check out our related article explaining step-by-step how to tighten a mountain bike chain. Then, to get the most out of your mountain bike and keep all the moving components working well, it is very important to maintain your bike’s chain and keep it clean with a chain cleaning tool kit like this. Have a look at this article by Cycling Tips for tips on how to care for your mountain bike chain. Occasionally, you may run across a mountain bike chain that keeps breaking. When you do, be sure to check out our related article to find out why.
And, as a matter of interest, if you are keen to do your own regular maintenance then check out our ultimate list of tools for mountain bike maintenance to see what tools you will need to keep your bike going smoothly.
How Long Should A Mountain Bike Chain Be?
The chain you choose for your mountain bike needs to be the right fit. To make the right choice of chain, two very important factors need to be considered; the gearing system of your bike and the size of your bike.
A mountain bike chain for an 11-speed drivetrain should have an external width of 5.5-5.62mm and an internal width of 2.18mm and a length of 12.7mm if the mountain bike needs a standard chain length. The length can vary depending on the number of teeth in the front and rear sprockets and the distance between the crank bolt's rear axle and midpoint.
Your bike’s gearing depends on the type of bike you have and what type of riding it is designed for. For example, downhill riding will require relatively small gears to enable pedaling down steep terrain, while big gears will be needed in rough and rocky terrain. So, the gearing of your bike influences how long the chain will be. The chain needs to also allow consistent gear shifting based on your bike’s design and riding purpose. Our article that discusses whether you can put drop bars on a mountain bike and why you should, discusses different types of riding in greater detail
A bike with a chainstay of 17.4 inches, having about 11teeth and 40 teeth on the largest rear cog and front chainring respectively, will require a chain that is 49 inches long. A trek mountain bike that has a chainstay 17.13 inches long with 9 teeth and 38 teeth on its largest rear cog and chainring respectively will need a chain that is 48 inches long. While the gearing and size of your bike affect the type of chain your bike will use, the length of the chainstay, the number of teeth on the largest front chainring, and the rear cog determine the exact chain length that will be a perfect fit for your bike.
Mountain Bike Chain Length Chart
Here is a table of the exact chain length that will work best for your bike based on the length of the chainstay and the number of teeth on the largest rear cog and front chainring:
|Number of teeth on the largest rear cog
|Number of teeth on the largest front chainring
|Chain stay length
|Bike chain length
|430mm (16.93 inches)
|433mm (17.05 inches)
|435mm (17.13 inches)
|442mm (17.40 inches)
|445mm (17.52 inches)
|440mm (17.32 inches)
|446mm (17.56 inches)
|436mm (17.17 inches)
|444mm (17.48 inches)
|439mm (17.28 inches)
The values in the table above may differ from your bike’s measurements. If that is the case, you may find it helpful to use the bike chain length formula that is discussed below. This formula can be used to accurately calculate the right chain length based on your bike’s specific measurements.
You may also be interested in learning our quick and proper mountain bike chain maintenance tips and tricks in order to keep your chain in tip-top shape. Be sure to check out our related article to find out more. Furthermore, you might want to also read our related guide to mountain bike chain guide installation for a step-by-step process to follow.
Regular Mountain Bike Chain Length Formula
The chain length of mountain bikes can be calculated using a simple formula.
The formula to calculate an MTB chain length is: L = 2 × C + F / 4 + R / 4 + 1 where L is the length of the chain in inches, C is the length of the chainstay in inches, F is the number of teeth on the largest front chainring, and R is the number of teeth on the largest rear cog.
This simple equation is more frequently used to calculate the chain length of mountain bikes with chainstay length (C) greater than 15 inches, and for bikes that have standard front chainrings and rear cogs.
Rigorous Mountain Bike Chain Length Formula
There is yet another complex formula, the rigorous equation for bikes that don’t have standard front chainrings and rear cogs.
The rigorous mountain bike chain length formula is TSPCL = 2 × √ (C² + (0.0796 × (F - R)) ²) + (F + R) / 4 where TSPCL is the theoretical shortest possible chain length in inches, C is chainstay length in inches, F is the number of teeth on the largest front chainring, and R is the number of teeth on the largest rear cog
This rigorous equation is used to calculate the chain length of bikes with more a complicated chain structure, usually bikes with a chainstay length less than 15 inches and bikes with a large front chainring and smaller rear cog.
As an example, to calculate the chain length of a mountain bike that has 40 teeth on the largest front chainring and 10 teeth on the largest rear cog if the chainstay is 444mm long, will be as follows:
- We would make use of the simple formula used for finding the length of the bike chain: L = 2 × C + F / 4 + R / 4 + 1
- The parameters that will help us find the length of the bike chain are given, but we will need to convert the chainstay length from mm to inches. The standard unit for length for this calculation is inches. So 444mm equals 17.48 inches.
- Using the simple formula, we have: L = 2 X 17.48 + 40 / 4 + 10 / 4 + 1 = 48 inches
The chain is a very important component of your bike as it is the part that keeps your mountain bike moving forward, that is why you need to make the right choice of chain in order to have pleasurable, safe, and stress-free riding. It is also important to maintain your mountain bike’s chain so that it lasts as long as possible as the experts at REI explain in this article.