How often should I replace my mountain bike chain?
There is no set mileage or timeframe, but you should replace your chain before there is considerable wear. The best way to determine when to replace your chain is by measuring your chain stretch.
The rate of chain stretch depends on:
Where you ride
Riding style
Weather/climate
Lubing schedule
Cleaning routine
What is ‘chain stretch’?
While chain stretch is used synonymously with chain wear, chains don’t actually stretch. As you ride your MTB, the chain wears at the rivets and rollers from straining against the rows of sharp teeth. As the rollers continue to wear down, the chain develops play or movement around the pins.
As the chain links continue to wear, you end up with a loose or ‘stretched’ chain. At this point, if you continue to ride with this worn chain, the chain will round the teeth of the gears, also requiring the replacement of the cogset.
Image Source: Wikimedia Commons
Replacing the chain & chain stretch measurements
Park Tool’s Chain Checker range of chain wear is from 0.0 to 1.0. These numbers are a percentage of 12 inches. 1.0 is one-percent of 12 inches or 1/8 inch.
Common chain stretch recommendations:
Above 12 1/8 inches (1.0) = replace the chains and cogset
12 3/32 inches (.75 percent) or less = If you want to avoid replacing the cogset then replace your chain at or below .75
How to measure chain stretch?
There are two primary ways to measure chain wear/chain stretch:
Use a ruler or tape measure (more accurate, assuming it’s measured correctly)
Measure using a bike specific chain checking tool
Lu (Pedal Chile staff) on her commuter bike in Chile’s Patagonia
measuring with ruler
Bicycle chains are made in inches and the easiest way to measure is by using a steel ruler:
Pick a rivet and line it up at the zero mark (make sure the master link is not being measured)
Count 23 more rivets and note the measurement of your last rivet (24th)
A new chain measures 12 inches
Your ridden chain should measure 12 inches and change
If the chain measures:
Less than 12 1/16″(.5 percent) = no chain replacement
12 1/16 - 12 3/32″ (.5-.75 percent) - ONLY need to replace the chain
However, it’s possible you might experience temporary skipping for the first couple of rides…if the skipping continues then time for a new cog(s)
Over 12 1/8 (one-percent)” = replace the chain and the cogset
Measuring with a ruler
measuring with chain checker tool
It’s easier to measure your MTB chain using a measuring tool, but they are less accurate than the ruler method.
There are numerous chain checking tools on the market to choose from. However, Pedal Chile doesn’t endorse or promote the use of chain checker tools, as the accuracy is beneath our standards. If you would like to use one, check-in with your local bike shop for best practices and models.
Even though we don’t use a specific chain checker tool, we do adhere to the chain stretch percentage or measurements, for replacing chains. This ensures maximum performance with minimal unnecessary wear on the drive-train system.
Chain pitch & width
The chain pitch or distance between links is the same on all modern bicycles and is 1/2 inch. You’re able to measure the ‘chain slack’ since ALL chains have the same chain pitch
The chain width varies by bicycle
signs that you should replace your chain
Time to replace this chain
Slower shifting
Imprecise shifting
Drivetrain noise
Rougher than normal pedaling - gritty feel
*These are all signs that you need to replace your chain.
Process of bicycle chain wear
Bicycle chain - Image Source
As your bike chain ages and is used, each link’s internal bushings slowly lengthen. This stretches your chain and puts added pressure on your cogs and chainring teeth, causing them to wear down faster.
This puts undress stress on the entire drive system and the worn-down chainring teeth have reduced shifting performance.
A chain that has been ridden too long will wear the chainrings and cogs. You will need to replace these bike parts as well as the chain if you wait too long.
Replace your chain before it’s worn. This will save you from having to replace the rest of your drivetrain.
chains & cogs wear together
Why does your bike mechanic recommend that you replace your cogs and chain together?
Drivetrain of a bicycle
The reason for this recommendation is because riding with a worn chain will wear out the cogs as well.
As a result, the new chain won’t mesh smoothly. You will experience lots of chain skipping and gear-shifting issues.
However, if you replace your chain before it reaches .75 (12 3/32”) stretch, you can avoid having to replace your cogs, since you replaced your chain before your cogs had a chance to become worn-down.
Many riders wait until their chain has considerable wear or mechanical failure before servicing.
At this point, the chain stretch is above one-percent, which means your cogs are also worn down and need to be replaced. This is why your bike mechanic will recommend replacing both at the same time.
BIKE TERMINOLOGY: Explained
What is the difference between cogset and cassette?
You have two sets of cogs, connected by a chain. The front cog is known as the chainset/chainring/crankset. A gear (sprocket) on the rear wheel is called a cog and a grouping of cogs is referred to as a cassette/cogset.
MTB chain wear vs road cycle wear
If you are pedaling up steep singletrack trails and riding in all weather conditions then your chain will wear much faster than road cycling. Some dedicated MTBers need to replace their chain every couple of months.
If you ride lots of trails and are constantly switching through gears while stomping on the pedals, you should be checking your chain stretch regularly.
Final Thought
There are many different viewpoints when it comes to chain related maintenance. For my beater commuter, I keep the chain properly lubed and that’s about it. On my high-end MTB, I measure the chain stretch regularly, as this allows for maximum drivetrain efficiency and is a preventative maintenance measure.
Jesse is Director of Pedal Chile, which is an all-inclusive MTB Tour Company in Chile’s Patagonia, where he lives. Jesse has a Master of Science in Health and Human Performance and is an avid MTBer, especially the singletrack around Pucón. Hobbies: Reading (mostly nonfiction) writing and sliding down mountains on bike or board.
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Sources:
Andrews, G., 2013. Complete Road Bike Maintenance. London: Bloomsbury Publishing.
Jones, C., 2013. Big Blue Book Of Bicycle Repair.
Milson, F., 2011. Complete Bike Maintenance For Road, Mountain, & Commuter Bicycles. Minneapolis: MVP Books.
Peter Ballin., 2017. Mountain Bike Maintenance. Crowood.