A chain is an incredibly efficient means of transferring power. However, the demands put on it by a modern mtb mean that its life is short. A chain is at its most efficient when kept clean, lubricated and running in a straight line but often chains are asked to perform in the opposite of these conditions. Also as mtbs have become equipped with more and more gears, chains have had to be made narrower to fit within the confines of our frames. As a result, this results in increased wear so a narrow nine-speed chain is more prone to wear than an older, wider seven/eight-speed chain. The quest for lighter bikes has even seen weight removed from chains — again increasing wear rates.
Neglecting your chain by leaving it dirty and underlubricated will greatly reduce its life. A worn chain will in turn wear a bike’s sprockets and chainrings, and this will lead to a much higher repair cost, especially for those running high-end groupsets.
The trickiest thing about replacing a chain is knowing when to do it. There will be no warning – gears will continue to work fine long after the chain has worn and has started to damage all it touches. A chain wear indicator tool is therefore essential to determine the state of wear. My own favourite is Park’s CC3C. At £7.99, it’s cheap and accurate.
Here we show you how to detect a worn chain and how to replace it properly. This procedure is easy to perform, takes little time and in the long run will save you money.


Chain Breaker / Chain Checker / Shock Pump (for full-sus bikes with an air shock) / Chain Lube

1 If your chain-wear tool does not sit in the links then the chain is not worn.

2 If your chain is showing 0.75 per cent wear you should change the chain, as this will get the maximum life from your cassette and chainrings.

3 If the chain is showing one per cent wear you should change your chain immediately and possibly the sprockets and chainrings — they may have worn to the extent that they will slip if you try out a new chain.

4 To remove a chain with a quick-release link follow the manufacturer’s instructions. The SRAM chain shown comes apart by pushing the ‘Power Link’ together then separating the two halves.

5 Never break a Shimano chain where it has been previously joined. See the connecting pin in picture.

6 To remove a Shimano chain you need to completely drive out one of the pins.

7 Place your new chain on the largest chainring and the largest sprocket, (without running through the rear derailleur) and add two complete links. Once run through, the rear derailleur should be at full stretch, as shown.

8 On a full-suspension frame, measure the chain while the bike is fully compressed. Release the air from your shock or back-off the spring preload to make this easier.

9 Remove any unnecessary links with your chain breaker. A Shimano chain should be left with male and female ends to enable joining with a new pin. SRAM chains should be left with two male ends to accommodate the Power Link.

10 Once the chain is correctly routed through the derailleurs it can be joined. SRAM chains are simple to join. Fit the two parts of the ‘Power Link’ together and pull apart to join securely. Always use a silver link for eight-speed chains and a gold link for nine-speed.

11 Shimano chains should also be joined with the correct pin: silver for nine-speed and grey for eight-speed.

12 Drive the new Shimano pin through the chain until it protrudes through the chain in the same way as the other pins.

13 Snap off the remainder of the pin using your chain tool or some pliers. Check that the link is not stiff. A stiff link indicates that the new pin was not set correctly.


Always lube a new chain with proper chain lube for best performance.

Keep some spare Shimano chain pins or Sram Power Links in your wallet so they are always to hand.