Did your bike start to make a funny ticking noise when pedaling? Or did your chain start to lose grip and slip right in the middle of that final sprint? These are common signs of chain wear which means it might be time to replace it.
First thing first, you’ll want to inspect your cassette and chain to figure out if they really are the culprits of your problem. Your chain is made up of a series of side plates linked together using rollers and rivets. Every kilometer you ride adds a slight amount of wear on your chain thus creating a bit of slack within the rollers. Over an entire chain length, the cumulative slack at each roller is called “chain stretch”. A chain is said to be at the end of its life when a 1% stretch can be measured using a chain stretch tool. While you’re at it, take a look at the smaller cogs of your cassette and look for teeth that appear to have been pulled and stretched towards the front of the bike. If your cassette is really worn out, it is good practice to replace the chain and cassette at once because your new chain’s spacing between each link would be tighter than the worn tooth spacing on your cassette.
Removing the Chain
There are two different scenarios here: either your chain has a master link, or it doesn’t. If your chain does not have a master link (Shimano), then the general procedure to removing the chain is first selecting a rivet that does not appear to have previously been removed. Your chain is made up of identical rivets except for 1 or 2 or 3 that look different on the ends. Do not select these rivets when removing your chain. Engage your chain tool and turn until you make contact with the chain rivet. At this point you’ll want to turn about 5 turns (depending on the chain and tool used), or until the pin is sticking out 80-90% of the way. Back out your chain tool and disengage it. At this point your chain should still be installed on your bike with one rivet protruding. Grab the chain on either side of that rivet and bend the chain to finally unlock and remove it.
In the case where your chain uses a master link (Wippermann), the only difference is that you do not need a chain tool to push a rivet out. Instead, inspect the particular master link you have at hand for a way to unlock it. You usually have to slide each master link’s side plates in opposite direction to disengage them. You can use long nose pliers to get this done.
A chain that is too long will sag along the chainstay when placed on smaller cogs and chainrings, while a chain that is too short will not allow reaching all gear combinations causing poor shifting. If you want to play it safe and that you know you’re replacing the OEM chain, then simply reinstall the same number of links as the manufacturer had installed. You might notice that with the same number of links, your new chain is a little shorter than your old chain. This is normal and caused by chain stretch as discussed earlier.
The other option is determining the optimal chain length yourself. To do this, place your shifters on the second largest cog in the back and on the largest chainring in the front; this is the second longest distance the chain can travel. Weave your chain through your derailleurs and pull the chain tight noting at which rivet the shortest chain length can possibly be installed. Note that when not using a master link, chains can only be joined at mating inner-outer-plates, while if using a master link, chains can only be joined at mating inner-inner-plates. From the shortest possible chain length you have determined can be installed, add an additional inner and outer plate. This is adding enough chain length to allow the chain to travel on the largest-cog-largest-chainring combination. Cut your chain using a chain tool.
Installing the Chain
The reinstallation procedure is essentially the exact opposite as the removal procedure; this sounds stupid, but it’s true. Once your chain is properly threaded though your derailleurs, I suggest you purposely derail the chain off the chainring, onto the frame. This will give you some extra slack for an easier reinstallation. Re-engage your master link and position it such that it is directly between your cassette and crankset. Holding the rear wheel stationary with one hand, apply a pedaling force on the pedal with the other hand. Because of the chain tension applied, the master link should safely snap closed.
If your new chain did not come with a master link, it instead came with replacement rivets that are roughly double the width of your chain. These rivets have a tapered pilot end that is used to guide the rivet into the chain roller. Once pushed in using the chain tool, the pilot end will protrude on the opposite side and can easily be snapped off using a pair of pliers, or the chain tool itself. In the end, your replacement pin should protrude as much on either side as any neighboring rivets.
Shimano design requires that the replacement rivet be the one first driving the outer plate of the chain into the rear derailleur.
Campagnolo design requires that the replacement rivet be pushed in from the chain plate facing the wheel, outwards away from the wheel.
Your just-installed replacement rivet might end up being stiffer than it really should. If that’s the case, place both thumbs on the stiff rivet and flex the chain side to side. Use care not to apply excessive force.
Well that’s about it; you’ve got yourself a brand new chain on your bike! Go on for a spin and don’t forget to follow basic lubrication habits to improve shifting performance and extend the chain’s lifetime.