What Happens If The MTB Chain Is Too Short (The Definitive Guide)

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What happens if the MTB chain is too short?

This might sound like a trivial question for those who are unaware of the nitty-gritties of mountain biking.

But bikers who have hit the trails multiple times would know that this question is not as insignificant as it may seem to be.

Proper chain length is vital for the optimal performance of a mountain bike.

It is not advisable to ride a mountain bike with a too short chain, as it could make shifting onto the large gear combination cumbersome or sometimes even impossible.


How To Check if The Chain is of Correct Length

Why Does The Chain Keep Slipping Featured Image
Mountain Bike Chain

First, to check if your mountain bike’s chain is of the right length, shift into the largest chainring and largest cog.

This shift should be seamless, and there should be two slight bends at both the rear derailleur jockey wheels.

You will notice this shift to be difficult if the chain is short.

In such cases, the derailleur cage gets stretched out in a way that it lays parallel to the chainset.

When the chain length is too short, then it could even become impossible to shift into the largest cog.

The other way to check the length of the chain that you are yet to place on the drivetrain is to wrap the chain onto the largest cog on the front and the largest cog on the back.

Hold the two ends together to determine how many links have to be added or removed for a suitable chain for this gear combination.

If you have to shorten the chain length of your mountain bike, remove the extra links and assemble.

Now you can test this by shifting the gear to a large cog in the front, a large cog in the back, a small cog in the front, and a small cog in the back.

Remember, this is only to test the length of the chain, and it is not at all recommended to ride with a large-large combination.

This may be detrimental to the drivetrain.


What Happens When MTB Chain is Too Short or Long

What Happens If The MTB Chain Is Too Short or Too Long-min
Right Mountain Bike Chain Size

1. MTB Chain Length Affects Shifting

The mountain bike chain length plays a significant role in facilitating gear shifting.

If the chain is too long, it could get dropped or may lead to inconsistent shifting of the front and back gears.

Things get worse when the chain is too short.

While you may already know that too short chains make it impossible to shift to a large-large gear combination, the repercussions could be higher­ if at all the chain shifts in such situations.

Having short chain for your mountain bike could damage the derailleur and the chain and lead to bends in gear teeth.

2. MTB Chain Length Affects Pedaling

Even though chain length does not affect speed, it may have an effect on the pedaling efficiency.

The number of gears is the most determining factor of speed.

However, if you are not able to shift to faster gear combinations, you may slow down due to the extra effort that goes into pedaling.

In short, chain length can have a significant impact on your performance on the mountain bike.


Factors To Consider For Better Chain Performance

The importance of regularly paying close attention to the chains cannot be overlooked.

You must be aware of when it wears out in order to make a timely replacement.

You must also know which chain is most suitable for your bike.

Having the right chain size and crank-derailleur combinations are essential factors to consider while buying a new mountain bike chain.


How To Connect The Mountain Bike Chain

Drivetrain Parts
Connecting Mountain Bike Chains

Multi-speed chains can be connected in two methods, as follows.

The Quick Link Connection method uses two removable outer links to connect the chain.

The Rivet Pin Connection method makes use of a special pin to connect the chain.

First, you need to find the right length of the chain by comparing it with your old chain.

In case you have added a new cassette with more cogs, you would need a longer chain.

It is always better to go with a new chain when compared to adding fresh links to an existing chain, as the chances are it is already worn out.

If yours is a single-speed bike, the chain setup is a bit different from the multi-speed ones.

They consist of master-link chains, with an outer plate, link, and circlip that is used to connect the chain.


Determining The Width of MTB Chains

Determining The Internal Width of MTB Chains
Measuring MTB Chains

1. Determine Internal Width of MTB Chain

Mountain bike chain’s internal width varies drastically and falls into the following categories:

  • Some single rear sprocket bikes have an inner with of 1/8” 
  • Some single rear sprocket bikes and bikes with 5 to 8 rear sprockets and derailleurs come in 3/32” internal width
  • Bikes that encompass 9 to 12 rear sprockets typically have a chain size 11 of 128.”
  • Freight bikes and tricycles typically come in 5/32” internal width
  • Derailleur bikes usually require a 3/32″ or 11/128″ internal width chain
  • A single-speed or internally geared bike would need a chain with an internal width of either 1/8″ or 3/32″ sprocket

2. Determine External Width of MTB Chain

In the case of single-speed bikes, the external width of the chain is not a matter of concern.

However, for a multi-speed derailleur bike, external width is important.

The number of sprockets determines the width required for the mountain bike chain.

If the chain has more sprockets, then its width should be less, and if the chain has less sprockets, then its width should be more.


Determining Internal And External Width of the Drivetrain

MTB Chain Drive Train
MTB Drive Train

Different drivetrain speeds require different combinations of external and internal MTB chain widths.

  • Drivetrain with 5,6,7, or 8 speed should have chains with 3/32” internal width and 9/32” external width.
  • The 9-speed drivetrain should ideally have chains with an exterior width of ¼” and internal width of 11/28”.
  • A 10-speed drivetrain should have chains with an external width of ¼” and internal width of 11/28”.
  • If your mtb has a 10-speed narrow bike chain, go for chains with a 7/32” exterior width and 11/128” internal width.
  • 11-speed drivetrains would typically require chains with 7/32” external width and 11/128” internal width.
  • Mtb with a 12-speed drivetrain would need chains with 13/64” external width and 11/128” internal width.

8 Common FAQs About Mountain Bike Chains

1. How many miles should the mountain bike chains last?

Expert mountain bike riders predict the mountain bike chains to last for 2,000 to 3,000 miles.

However, the durability of your mountain bike chains depends mainly on your style of riding.

There are riders who change their bike chain every 2 to 3 weeks due to the excessive, hard use of their bike.

If you frequently ride on tougher terrains or use advanced riding techniques, it may require you to change the chain more often.

The more often you change the chain, the better longevity for your drivetrain.

Cleaning, proper lubing and maintenance of the chain will help in improving the durability of your mountain bike’s chain.

If your riding style does not put any pressure on the gears, and you are not a consistent rider, you could get your chain live up to even 8000 miles.

However, always pay close attention to any signs of elongation or wear in the chain.

Make sure you are not leading the drivetrain of your bike into a mess by trying to enhance the lifespan of your chain.

2. Are all mountain bike chains the same size?

Bike chain sizes vary from bike to bike. So if you are looking for a universal bike chain, you may be disappointed.

It is essential to understand the different sizes before you set out to replace your mountain bike chain.

To make an informed decision, you need to have a basic idea about chain length and width.

Below are the two chain size variables:

A. Link Pitch

Link pitch refers to the link length, which is essentially the distance between two pin centers.

For example, 0.5 inches is the standard link pitch for the present-day bike chains.

Even though there were other link lengths in the past, 0.5 inches is commonly found these days.

B. Total Length

When you multiply the 0.5-inch link pitch by the number of links, you get the total length of a chain.

The total chain length varies from 100 to 126 links, the popular being the 116 links.

3. What is the standard chain size for a mountain bike?

There is no one-size-fits-all mountain bike chain.

The chain length and width vary depending on the nature of the drivetrain.

However, the different sizes of bike chains to go with different drive trains are covered in the above drivetrain section.

4. How do I know the chain size of my mountain bike?

To understand the chain size of your MTB, you need first to consider your drivetrain speed.

Please refer to the drive train and internal and external width combinations section above for reference.

5. How to size a new bike chain with the old one?

Old mountain bike chain with an acceptable length can be taken to measure the length of a new bike chain.

To do this, lay the old chain next to the new chain.

It is better to go a bit shorter, as chances are, there is some extra slack on the first chain due to excessive use.

When you line both the chains together, make sure that the outer plates of the old chain are with the other plates of the new chain and same goes for the inner plates.

For an accurate comparison, insert a master link if the outer plate end is compared with the inner plate end.

Make sure that a rivet-to-rivet comparison is being made.

6. What is a mountain bike chain made of?

A mountain bike chain is made up of steel, carbon fiber, and aluminum alloy typically.

Before you make a replacement or change to your chain, get an expert help to make sure that it is compatible with your mountain bike.

7. When to replace a mountain bike chain?

You can replace your mountain bike’s chain when you start noticing the wearing off of the metal pins that bind the chain together.

Losing the teeth and sprocket cogs is another sign that your mountain bike chain needs to be replaced soon.

It is recommended to replace your mountain bike chain as soon as you notice any wear, as otherwise, it could damage your drivetrain cassette and sprockets as well.


That’s All

I hope you found this article helpful in understanding what happens if the MTB chain is too short.

Moreover, I am sure you might have noticed additional factors that matter with regards to getting your mountain bike chain length right.

P.S. If you found this to be helpful, do check our similar in-depth resource on long MTB chains, how to choose a mountain bike chain and prevent it’s slippage from your bike.

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Team Biking KnowHow

Rohan runs Biking KnowHow along with his team. Rohan has been a mountain biker since 2005. His mission is to simplify mountain biking for everyone. All Biking KnowHow content piece is thoroughly fact-checked. Our content is backed up with leading research and inputs from expert cyclists.