Do you need a new chain? Find out the easy way to tell

Your bike chain will gradually wear with use and will need changing from time to time in order to maintain your drivetrain’s performance. Worn chains shift poorly, wear sprockets quickly, and sometimes break. 

So when should you change your chain?

“For chain replacement we do not state 'every x kms' as this is not possible,” says SRAM. “Chain wear is based on multiple factors including maintenance (clean/lube), use conditions (water/mud/sand), user shifting patterns and overall drivetrain condition (cassette/ chainring wear).”

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Campagnolo agrees.

“It is difficult to pin down an exact number to kilometres due to the fact that riders come in different weights and sizes, ride differently, shift more or less frequently, develop more or less wattage, ride on flat or hilly terrain, clean or nasty conditions, take care or leave their chain dirty… all of which create large variables in just how much wear and tear is created,” says Campag's Joshua Riddle.

“It can vary between 3,000km to 8,000km generally speaking, but it could be less or even more in some cases.”

First, you need to replace your chain when you spot any damage (a deformation or crack). You should also check your chain regularly to see if it has worn to the point that you need to change it. 

There are several ways to check whether your chain has reached this stage?

Measuring with a ruler

You can check for chain wear with a ruler. It’s a little easier if you go with imperial measurement here because one complete chain link of a standard chain measures 1in.

Start at one link pin and measure 12 complete links. You need to put some tension on the chain to be accurate.

On a standard new chain, 12 complete links will measure 12in, but when a chain is worn the 12in mark of the ruler won’t quite reach the relevant link pin.

If the distance from the 12in mark to the centre of the link pin is less than 1/16in, your chain is fine, but if it gets to 1/8in (or 2/16) mark it has gone beyond the point at which it needs replacing.

If you use metric measurements, it’s easiest to measure 10 links.

On a standard new chain, 10 complete links will measure 25.4cm.

If the distance from the centre of one link pin to the centre of the link pin 10 complete chain links away is up to 25.5cm, your chain is fine, but if it gets to the 25.6cm mark it has gone beyond the point at which it needs replacing.

If you want to get more accurate, it's usually advised that you replace chain designed for 10 or fewer gears when it has lengthened by 0.75% – so when 10 links measures 25.59cm – and that an 11-speed or 12-speed chain is replaced when it has lengthened by 0.5% – so when 10 links measures 25.53cm. 

If you have a one-speed or two-speed bike, replace your chain as it reaches 1% wear - so when 10 links measures 25.65cm.

Figures like these are obviously very difficult to gauge with a normal ruler, which is why we'd advise the use of a chain wear indicator.

Chain wear indicator

A chain wear indicator, sometimes called a chain checker, is an inexpensive gauge that does exactly what its name suggests. 

This is Park Tool’s CC-3.2 chain checker with an RRP of £9.99, although you’ll find it cheaper if you look around. Other brands offer similar instruments.

You hook the curved end into the chain and if the gauge tip on the other end fits completely into a chain link, the chain is worn to the point it needs replacing (one side measures 0.5% wear, the other side measures 0.75% wear). 

Measuring by eye

There’s one other simple method of checking for chain wear. 

KMC advises, “If you do not have a gauge to test the chain’s elongation you could roughly check by putting the chain on the outer chainring and lifting up the chain from the middle of the chainring. If you can lift it more than half a link, the chain or chainring, or both, are probably worn.”

The chain in the picture is almost new so minimal lift from the chainring is possible.

Check out our advice on how to replace a chain.