Your bicycle chain should not be too long or too short for your drivetrain. To measure the correct length, check it against your current chain with a ruler.
Can a short bicycle chain damage my bike? Yes, if you ride on an incorrectly sized bicycle chain, it can cause damage to your components and/or the frame of your bicycle. It is possible for a bicycle chain to be too short but not beyond the point of causing damage. It is also possible for a bicycle chain to be too long and will not cause any damage. In either case, if you are unsure whether your bike chain is the correct length or otherwise damaged, it should be replaced with a new one immediately.
A bicycle chain is perfectly fitted when it has the correct number of links (for example, a 130 link chain will fit for 130 centimeters between the bottom bracket and the rear sprocket; this value must be based on original equipment), and its length allows no more than two inches (about 5 cm) of play in the upper run. The correct length of the chain is dictated by the size of the cogs on the rear wheel.
If you haven’t replaced your drive chain in recent years, it’s possible that your currently installed bicycle chain may be too short for your current setup. This can happen particularly if you have a triple-crank setup. Your crankset might have a 52-tooth large chainwheel and a 39-tooth small chain wheel, or perhaps even a 50-tooth and 36-tooth. If you shift to the smallest sprocket (the one with the fewest teeth), you will find that there is not enough slack in your bicycle chain to allow it to shift onto the small chain wheel.
The same problem can happen if you use a mountain bike crankset (with inner rings of 48T and 38T) with a ten speed block – the smallest sprocket on your cassette will cause the bicycle chain to be too short for your gear setup.
To test your old bicycle chain, shift down to the smallest cogs on your rear wheel and hold the back end of the bicycle chain at that cog. If you can bind or catch more than three links, then you will need a new bicycle chain.
How to tell if a chain is too short?
The best method is to make certain that the old chains is neither too long nor too short by checking with a ruler against your current drive chain. The drive chain must include the length of the rear derailleur, which is not always proportional to the size of your cogs or chain wheel.
For example, if you have a 10 speed setup with an 11-tooth cog on the cassette, there will be less distance between that cog and your small chain wheel. A 9 speed derailleur may be required for this setup, which will increase the length of the derailleur. The distance between your cassette and rear derailleur must match the distance between your current chain wheel(s) (measured at the crankset) and rear sprockets (measured at the hub).
Conversely, if the wheel has more than 11 teeth, you will need to decrease the distance between your cassette and rear derailleur appropriately.
If you are certain that your current bicycle chain is neither too long nor too short for your existing setup, then it may be time to buy a new one. If in doubt, this old rule of thumb can be used to measure the length of a bicycle chain:
“Measure from the center of the crank bolt, to the middle of 12t cog, plus 5 inches.”
This will give you an idea of what size bike chain to purchase. If your current 1/8″ (3mm) thick bike chain is about one inch longer than the length described above, then you should purchase a 1/8″ (3mm) bike chain. If your current bike chain is much longer than one inch, then you may need to switch to a 3/32″ (2.4mm) bicycle chain.
Remember that this rule of thumb does not take into account the distance between your cassette and rear derailleur, so you will need to measure this distance.
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Bicycle chains can wear out over time. The metal pin(s) that hold the chain together can break, or the teeth on your cogs, sprockets or chainrings may wear down. When the bicycle chain wears out, it is usually replaced with the same chain type it is replacing. For example, if you are switching from a 1/8″ bike chain to a 3/32″ bike chain, there should be no need to measure your drive chain for length – simply replace your old 1/8″ bicycle chain with a 3/32″ bicycle chain.
If you have a longer drive chain, or if you wish to use smaller cogs for easier pedaling, it may be necessary to buy a new bicycle chain that is one size smaller. The same rule of thumb used for measuring a bike chain can be used to determine whether a particular 3/32″ bicycle chain should be replaced with a 1/8″ bicycle chain or a 1/4″ bicycle chain.
In the case that you have an extra cog on your rear wheel, it is possible to replace this with a smaller cog and create more slack in your drive chain to avoid having a bicycle chain that is too short for your gear setup.
Bicycle chains can be made from many different materials (steel, aluminum alloy, carbon fiber) and can be of varying quality. If you are still riding the same bicycle that you started on, it may be time to get a new bicycle chain if your current one is worn out or damaged.
When should my bicycle chain be replaced?
Over time, the metal pin(s) that hold the chain together can wear out. When this occurs, the bicycle chain needs to be replaced. If you have lost some teeth on your cogs or sprockets, it may also indicate that your bicycle chain is worn out and needs replacement.
There is no definitive answer as to how long a bicycle chain should last. It is usually replaced when it starts skipping teeth on your cogs or sprockets or when the metal pin(s) in the chain is worn out and need replacing. Bicycle chains can vary in quality, so this will also affect how often you need to replace your bicycle chain.
A bicycle chain is made from many different materials (steel, aluminum alloy, carbon fiber) and can be of varying quality. If you are still riding the same bicycle that you started on, it may be time to get a new bicycle chain if your current one is worn out or damaged.