Measuring bicycle chain wear

Some people aren’t really into DIY bike repair and that’s fine. I completely get why, my days of rolling around under vans and cars are over. But even if you’d rather hand your bike over to someone else for fettling there is one maintenance check that you cannot overlook – measuring bicycle chain wear.

How long should bicycle chain last?

Search through any bike forum and you will see numerous threads on the subject. Some will claim 6,000 miles is the norm and will angrily denounce anyone who comes up with a lower figure as a Shimano spy intent on selling you a chain. Like anything else though there are too many variables, such as your power output, the effectiveness of your cleaning routine, the lube you use etc. that will drastically affect how long your chain will last and prevent you from deciding purely on mileage when to change a chain. Realistically we rarely get much more than 1,000 miles out of a chain before it reaches the wear limit, in the case of an 11 speed MTB chain more like 400 miles seems to be the norm.

The good news is it’s easy to see for yourself when a chain is ready for the bin.

My chain looks fine to me, do I really need to change it?

Except in extreme cases (where the chain and or cassette/chainrings have been ridden to death) you can’t really see with the naked eye. Although there probably is such a thing as chain stretch for most part the increase in chain length is caused by worn pins, lins and rollers which causes an increase in distance between each pin.

This is a problem because as the distance between the pins increases, instead of the rollers landing neatly between the teeth on your chain rings/cassette, they begin to land on the edge of them. This in turn accelerates the wear on your groupset.

This wear becomes more obvious when you use your least favorite gears, say first, which will be noticeably more noisy than the rest. That’s the noise of your chain shaving your cassette’s teeth, what you are hearing is your cassette crying. However, you may only be able to tell on a slow, steep climb without any wind or if the bike is on a stand.

So how do I measure chain wear and how worn is worn?

Most manufacturers recommend changing a chain at either 0.5% or 0.75% wear. You don’t necessarily need a

chain measuring tool, although they do make it nice and easy – Park Tools CC-3.2 or the CC-2 (pictured) are great, however a steel ruler or tape measure will do just fine.

Assuming you are using a ruler etc. it’s easiest to measure in imperial (feet and inches) rather than metric:

• The pitch or distance between each pin is 1/2″ so 12 complete links on a brand new chain will measure 12″ from the centre of one pin to the centre of the one at the 12″ mark.
• If the link pin is less than 1/16″ (each increment is a 1/16″ on an imperial ruler) past the 12″ mark you don’t need to change it.
• If the link pin is past the 1/16″ mark you need to change the chain ASAP.
• If the link pin is past the 1/8″ mark you will probably need to change the cassette and the chain.

So why do I need to change my cassette and chain rather than just the chain?

If you have measured your chain wear at beyond the 1/8″ mark you will almost certainly have worn the teeth on your cassette excessively to the point that a new chain (without the aforementioned “stretch”) will skip, at least in your favorite gears. Even if by some miracle the chain doesn’t actually slip the chain will “ride high” on the cassette part way up the teeth. This will result in accelerated wear to your nice new chain.

But why keep changing my chain all the time? Would it not be cheaper to just keep riding my bike until everything needs changing in one go rather than changing my chain regularly?

Our advice is check the chain wear every few rides. Leaving it longer than described above is just false economy, even if you have a budget groupset that you believe doesn’t warrant spending the money on a fresh chain, once you pass that 1/16″ point you’ll find that the your drive train won’t last long at all. More importantly life is too short to ride rough bikes and once you pass that point, the drive train will feel rough.