Regular chain replacement is crucial for the continued smooth running of your bike and can save you hundreds of pounds in replacing other, prematurely worn drivetrain components.
We caught up with Jon Hayes, mechanic at Dorset bike shop, Ride, for advice on how to replace a chain: checking for wear, removing, measuring the length of a replacement chain and installing it.
in this in-depth video edit, Jon demonstrates replacing a chain on a 10-speed, Shimano 105 drivetrain, but discusses the idiosyncrasies of systems from the other big players in the component market: Campagnolo and SRAM.
Checking a chain for wear
Deciding if a chain should be discarded and replaced is the first step in the procedure. A chain’s component parts – the rollers and side plates of the links – become stretched by the tremendous tension generated by pedalling forces. There are several tools on the market to measure chain stretch, and Jon uses a Park Tool CC2 in the video.
Continuing to use a worn chain can cause premature wear to other, more expensive components in the drivetrain, notably the cassette and chainrings. The teeth on both are shaped over time by the chain and a stretched chain will deform them. Timely replacement should ensure a ratio of three chains to every cassette. Having to replace a cassette with each worn chain can be an expensive business.
Removing a chain
Jon begins by removing tension from the chain by shifting to the inner chainring and the smallest sprocket. Before removing the chain, he checks its length to judge if it can be used as a gauge for the replacement. The chain shown in the video is the correct length: it brings the derailleur into tension (pulls it forward slightly on its pivot) despite the chain being at its slackest. Longer chains are required for larger cassettes and chainrings: a consideration, perhaps, if you’re planning to fit a larger cassette to tackle the major climbs of one of the big European sportives, or moving from a compact chainset to a standard with the start of the racing season.
With a link selected, Jon applies the chain splitter tool to the chain and pushes the pin from the link. The drivetrain shown in the video is a 10-speed Shimano 105 system, and Jon warns of the need to use the correct joining pin. Different widths are used by the Japanese component giant for its eight, nine, ten, and 11-speed systems. He adds that the joining pin is non-removable (Campagnolo use a similar, if slightly more sophisticated system that requires a special tool) and advises to find another pin in the system to remove the chain if you intend to re-use it. SRAM uses a joiner link system that for its nine-speed systems can be removed by hand. SRAM’s 10-speed systems use a similar solution, Jon adds, but warns that the link should not be removed.
Fitting a new chain
Jon unpackages a new Shimano 105 chain. While chains are interchangeable between manufacturers (although never with ‘speeds’ – a 10-speed chain, for example, must always be used with a 10-speed system) Jon prefers to match the brand of the chain with the manufacturer of the other drivetrain components. The Shimano chain is pre-lubed, and it isn’t necessary to add extra before the first ride.
He drapes the chain over the smallest sprocket before routing one end through the front derailleur and draping it over the inner chainring. He feeds the other end into the rear derailleur and carefully threads it over the jockey wheels, ensuring that it runs behind the small, metal guide tab present on most rear mechs.
By pulling the two ends of the chain together until the derailleur comes into tension, Jon is able to gauge its length. Fresh from the packet, it is too long, and he decides to remove some links, ensuring that he finishes with a male and female end at the opposing ends of the chain. He describes the purpose of the various slots in the chain splitter tool, and which to use to remove a link.
Jon removes the joining pin from its packet and, holding together the two ends of the chain, inserts the pin, with the round end first. He gently pushes it into place with the chain splitter tool and snaps off the guide pin with pliers. It’s important to check the link isn”t stiff, and if it is, to use the second slot on the chain splitter tool to ‘open’ it slightly. In the example shown in the video, it doesn’t prove necessary. Jon completes the procedure by checking the function of the gears, shifting rapidly up and down the cassette, and across the two chainrings.