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Chain Repair

This section is for on-trail or temporary repair of a broken chain. In general, we recommend replacing your damaged chain with a new one as soon as possible. Test the chain for wear described in the Chain Care section. It's also possible that the force that broke your chain has twisted another link, or has splayed the outer side plates near the break. (Only a matter of time until it breaks again, usually at the worst moment...) To install a new chain, see the section on installing a new chain.

Inspect the broken chain. Usually, the link right at the break is warped and should be removed. Plan to "break the chain" where you'll have outer side plates on one end, and an inner side plate link facing it.

ch-brk01.jpg (18060 bytes)

Using a chain-breaking tool, push the pin out of the bushing. Check the position of the pin frequently. Stop turning when the pin is just on the edge of the bushing, before it begins to move through the outer side plate. (This is about 6 complete turns of the chain tool.) Now back the chain tool out of the bushing.

Removing the damaged link.

ch-brk02.jpg (15502 bytes) Wiggling the chain slightly side-to-side, extract the end of the chain containing the inner side plates, roller, and bushing from the outer side plates. The pin should still have a whisker of shaft visible on the inner side of the outer side plate.

Position of the pin after removal of link.

ch-brk03.jpg (13413 bytes) Now route the chain. To keep tension at a minimum, lay the chain on the bottom bracket at the front (just off the small chain ring to the inside), and route it over the smallest cog at the rear (move the derailleur over so it matches). Pass the chain on TOP of, then in FRONT of the upper pulley, then straight down to the bottom pulley. The chain passes BEHIND the bottom pulley, then forward UNDER it. (Remember FOUR sides of TWO pulleys.) If you have a chain retaining tool, hook it to the chain to keep the tension off. Otherwise, have someone hold the chain in position for you.

Routing the chain through the pulleys.

ch-brk04.jpg (17207 bytes) Align the chain end with the inner side plates so it fits inside the end containing the pin and outer side plates. Using the chain tool, push the pin inward until it's evenly spaced within the outer side plates.

Pushing the pin into the joint.

ch-brk05.jpg (11946 bytes) The newly joined link will be stiff. Work the repaired link up and down, and slightly side-to-side until it bends freely.

If you had to remove a damaged link for the repair, the shorter chain may not allow you to use "extreme" gearing combinations, such as your big chainring plus your biggest cog. (You shouldn't be using this combination anyway.)

Working the chain to remove stiffness.

Tip #1: Retaining Clip

It's much easier to to fix the chain with a "retaining clip." This is piece of springy wire that holds the ends of the chain while you work with it.

The clip in the picture is just a piece of a wire clothes hanger, bent to shape. I keep this in my toolbox.

With the clip in place, you're free to work on the chain without the tugging of the spring on the idler pulley of the rear derailleur.

And once you've split the chain, it remains in place, instead of falling around the chainrings or through the rear derailleur.

This makes it easy to put the chain back together.

chainlnk.jpg (12632 bytes) Tip #2: Quick Link

Many of us carry a connecting link. This link joins two inner plates together with less stiffness (you'll still need a chain tool to remove the old outer side plates). You need to have the right size (7-speed and 8-speed rear cogs use the same size chain, but a 9-speed uses a thinner chain). It's dirt cheap, and makes it easy to take the chain apart again.

Another option: A "Quick Link" connects the chain after removal of damaged outer link.

To insert the quick-link, replace the side plates (the two metal parts of the wider link) with the two halves of the quick-link. After pushing the pins through, so they're visible sticking through the hole, pull hard on the chain. As the link lengthens, the pins snap into place in the narrower end of the hole.
To remove a quick-link from your chain, squeeze inward on the link -- push the side plates towards each other. Then while holding that inward squeeze, compress the chain lengthwise so the end of the pin slides back into the larger side of the oblong hole. You can then pull the link apart.
Tip #3: Breakaway Pin

Connecting pins are available that have a tapered guide. You insert the guide into the link, then use the chain tool to push the pin into position. Then you break off the guide by twisting it with a plier. This gives a solid repair, and may allow you to make a repair without losing length. (Shove the old pin out at the break, then reassemble with the breakaway pin.) If you're buying a set of pins, be sure to order the correct size -- 8-speed (same as 7-speed) vs. 9-speed.

After the repair:  Make plans to get a new chain soon. A repaired chain may have subtle damage that can wear your chainrings. Or it may break again at an inconvenient time.

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