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While trying to put a new chain on a bike, I rather stupidly removed the "wrong" link in the chain, and it's already very short, so I can't simply remove yet another link in order to get the "correct" combination of links for connecting the chain back together (see the parts in the photo); Is there any way to put the chain pins back in in order to make the chain useable?

Chain with wrong link removed

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    This is the cycling version of measure twice, cut once :-)
    – andy256
    Oct 16, 2016 at 23:18
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    You can get the pins back in, but be sure to place any small children out of earshot before you start, because there will be cussing. And, unfortunately, the pins will not reliably stay in place once you do this (the left-side link looks mangled already), so plan on replacing the chain or splicing in some new bits ASAP. (And you definitely need a chain tool.)
    – Daniel R Hicks
    Oct 17, 2016 at 2:01
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    @andy256, what I love most about Bicycles SE is that stupidity gets upvoted here whereas on e.g. SO it gets downvoted... hence my reputation here being better than anywhere else.
    – errantlinguist
    Oct 17, 2016 at 7:16
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    @errantlinguist That's true. I think that on SO there's an element of RTFM, and downvoting LMGTFY questions. Here we're about answering questions, so that we become the, er, manual. Everyone's a n00b sometime. At the time of writing, the Famous Question gold badge has been awarded 575 times, mostly to members with quite modest reps. To get 10,000 views means a lot of people wanted an answer, so maybe the "dumb" question wasn't so dumb after all. Answering questions is what SE is for.
    – andy256
    Oct 17, 2016 at 8:51
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    @errantlinguist yes, this is why questions are not deleted, but closed as duplicates and kept. It does help finding, as like you said the wording can be different
    – njzk2
    Oct 17, 2016 at 15:38

8 Answers 8

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It's safer and way easier just to buy another MissingLink (KMC's name for their master link design) of the same type (pin length) the chain came with, leaving you with an inner link that has one on either end. They're around $2US.

In addition to saving the trouble of getting the pin back in there, there's also the question of the integrity of modern outer chain links once they've had a pin pushed back through, even in the more normal circumstance of pushing a link halfway out for chain removal. Every current major manufacturer of derailer chains except KMC says not to do this, due to the risk of the fit not being as tight after re-insertion as it's supposed to be. I've long wondered whether there's actually anything different about KMC in this regard, but I know that modern chains in general are prone to breaking, usually during hard or fumbled front shifts, when they've been reconnected the "traditional" way. I wouldn't venture to guess what the odds are of it happening, probably quite low, but putting in another MissingLink eliminates the risk. They're very trouble-free. Having a couple close together may seem goofy but doesn't cause any issues in practice.

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  • This is the right way to do it on a modern chain (the chain in question is a KMC chain).
    – Batman
    Oct 16, 2016 at 16:33
  • IMHO, this is one of many funny bicycle parts "lawyer notes". Most chain link can sustain few protrusion. Yes, pin holes will wear off and the plate will brake if pin protrusion are press too many time, only with improper tools abuse(e.g plier, hammer,etc). That's why the "don't do it" come into the picture.
    – mootmoot
    Oct 17, 2016 at 9:09
  • Might anyone be willing to send a MissingLink to Western Europe in return for compensation?-- here, it seems only rich people ride bikes, as after 2+ hours of checking bike shops, the best solution I've been offered is to be sold a new chain for the equivalent of $34 USD.
    – errantlinguist
    Oct 17, 2016 at 12:06
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    The SRAM PowerLink (equivalent from SRAM) is 1 euro on RoseBike, and any bike shop which sells Shimano/SRAM stuff will carry it (or an equivalent, e.g. from Wipperman) for closer to 5-6 bucks in this area.
    – Batman
    Oct 17, 2016 at 16:33
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    If one puts all the given answers together, you get a complete answer. In the days of 5-speed freewheels (and before), one would use a chain tool to remove the rivet and put it back to reassemble the chain (SOP, no safety issue). Narrow chains came along, and re-using the same rivet became a potential safety issue. Shimano uses special replacement rivet pins. IDK about KMC, but one of the other answers says they also have replacement pins available. You still need a chain tool, which is cheap and easy to find. EZiest answer is MissingLink.
    – Mark G B
    Oct 17, 2016 at 17:29
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This article titled, How to Get the Pin Back Into a Bike Chain, will give you a step by step guide on how to put the pin back in a bike chain.

Edit: I'm copying the article just in case the link ever becomes broken (no pun intended). The information below is from felixarizona.com

Edit 2: I removed the content that can be found here for possible copyright and rule violations. I recommend going to that article though for pictures of the different steps.

To make your life easier you are going to need a bike chain tool.

First you want to align the holes in the chain in preparation for the pin. Place the pin in the hole in the chain and push with your finger or gently tap with your finger. You don't want to push the pin all the way through until you have the hole on the other side of the link ready. With the chain tool punch the pin the rest of the way through the link. If there is very little force required to push the pin through, you may want to consider a new chain or at the very least a new link.

Then repeat the same process in order to complete the chain. Once you start doing it you will find that it is pretty straight forward.

Again, depending on how old the chain is and whether or not you want to risk it, you may want to just get a new chain.

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    +1 for including the relevant information AND linking back to the source.
    – Criggie ♦
    Oct 16, 2016 at 19:14
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    @Criggie On the contrary, I think this violates copyright and SE rules. The material should be summarised. -1 from me.
    – andy256
    Oct 16, 2016 at 22:14
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    @andy256 I understand both sides of the argument. The article in question seemed like it hadn't been updated in a while which made me think there was a possibility that it wouldn't be hosted in the future. I will modify it when I get a chance.
    – npsantini
    Oct 16, 2016 at 22:31
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    Good work @npsantini. Upvoted (I hate down voting).
    – andy256
    Oct 17, 2016 at 1:37
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    Sadly the felixarizona.com content now seems to have gone 404. Would re-pasting it still be copyright violation?
    – Ed Randall
    Mar 8, 2020 at 8:09
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With older style chains which were designed to be split and joined with a chain tool, the simple fix here would be to use some of the excess chain you cut off of the new chain (they're always too long) and (using a chain tool) splice an extension to the piece you're going to use.

With the newer narrower chains, however, this approach is less reliable.

(Hint here: Read the chain tool instructions! When "breaking" the chain you never push the pin ALL the way out, but stop a turn or two short of that point. If you get it right the pin should just barely project past the inside surface of the plate. If the instructions do not tell you how many turns, use the tool on the last link of the too-long chain and count how many turns it takes to push the pin all the way out. Write that down, minus two turns.)

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  • I don't think I've bought a newer chain that didn't come with a quick link or break away pin in a long time, even for 7-8 speed.
    – Batman
    Oct 19, 2016 at 6:45
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Today I discovered a fast method of getting a loose pin back into chain without any special tools. Not recommended except last resort!

  1. Stick screwdriver/spanner between the open ends of the outside part of the chain and twist so the holes are pushed out of alignment (and probably bent slightly outwards too). The open ends of the outer part of the link should be offset by about 45°, like scissors.

  2. Place pin inside the inner part of the chain, should be easy because inner part has a wider diameter.

  3. Place the inner part on the outside of one of the open ends, so the inner part of the chain is now acting as a guide to hold the pin in place against the outer part.

  4. Lay it on the ground and smack it with a hammer until the end of the pin goes back into the outer piece. Lift the inner end of the chain off the pin.

  5. Lay the outer end of the chain flat so the pin is now horizontal to the ground. Apply hammer again to the outer piece (the bit without the pin in) until the holes of the outer pieces are back into alignment.

  6. Now use chain tool to screw pin back through all pieces as normal.

All in all it took about 2 minutes to put back together, after my hour of failing with the chain tool. However clearly this is pretty bad for your chain. Using the hammer will probably leave some deformations on the outer chain link and the pin fit might not be as tight as before. Maybe as a last resort to get you to a bike shop...

I'd also recommend avoiding cheap chain tools because the one I bought for rock bottom price broke after one use - the pin on the tool bent outwards. Bad tools make a troublesome job even worse. I guess I learned my lesson about pushing the pin too far through now!

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  • +1 for "not recommended" Can you expand to say exactly what is wrong with this bush-fix? I guess it leaves a loose pin that is liable to fail soon and drastically under load.
    – Criggie ♦
    Jan 15, 2018 at 0:13
  • Yep I guess 'bush fix' sums it up nicely. After doing this to my old chain, the chain seems solid enough and moves freely, but you can see slight deformation from the hammer on the outside of the link. It will last me for my commute until new chain arrives, but I won't be trusting it 100%.
    – Phil B
    Jan 15, 2018 at 2:15
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Without specialist equipment, the only practical/reliable way to replace a chain pin is to buy a new one designed specifically for that purpose

http://kmcchain.us/connector/bullet-pin/

but at the price of the pin + the need for a chain tool, buying another quick-link (missing link) or even another full chain might be the best option.

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    You need the chain tool for shortening the chain in the first place; the only way you can get away with running a properly sized chain without needing a chain tool is to somehow get a perfectly sized chain in the package (or if for some odd reason, your bike shop buys chain in bulk, get them to cut the appropriate number of links).
    – Batman
    Oct 17, 2016 at 16:30
  • True enough batman!
    – zeFrenchy
    Oct 17, 2016 at 16:45
  • The KMC Bullet Pin is for their halflink BMX chains only. They don't sell consumer-level replacement pins for derailer chains. (Factories do use them I believe.)
    – Nathan Knutson
    Oct 18, 2016 at 19:00
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    Shimano chains are normally supplied with a pin you can use once to join the chain but I've never seen that same pin for sale separately.
    – Chris
    Oct 18, 2016 at 19:17
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    @Chris - I have seen bike shop guys with bags of the Shimano pins, so I know they're available separately.
    – Daniel R Hicks
    Oct 19, 2016 at 0:34
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Assuming there is leftover chain from shortening it, this is what I would do:

  1. Completely remove the outer link at the end of the chain (i.e., the one with one pin missing due to your mistake). When you do this, practice removing the link without completely pushing out the pin, e.g., push it out little by little (possibly counting turns for future reference), or set a limiter screw if your chain break tool has one.

  2. From the leftover part of the chain, break off a segment consisting of two outer links and two inner links (i.e., outer-inner-outer-inner), such that you don't fully push out the pin of the outer link at the end of the segment. (This time you should succeed, the one in step 1 was for practice. =)

  3. Join the segment to the inner link now at the end of your chain. When pushing the pin protruding from the outer segment back in, make sure you don't push it through all the way. Try to flex the chain at that link - if it feels stiff, push the pin the other way a little bit and try again. Repeat pushing that same pin back and forth in very small increments with the chain break tool, and keep flexing the chain until it is no longer stiff.

(For reference, I use similar-looking KMC chains and I always use the leftover parts to join into a new chain, in my experience the re-joined chain works just the same as the factory-joined ones.)

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You can't put an ordinary pin back in with today's chains unfortunately, but if the chain is of the type that takes reinforced pins, you can put a NEW UNUSED reinforced pin in. It costs slightly more but less than throwing away the chain.

I remember a long time ago I didn't like the way Shimano forces people to use single-use reinforced pins, and wanted a chain that has reusable pins. Then I noticed some few years old PDF specs of SRAM chains that listed several models and explicitly said that you can not only use the stupid quick link (should be called a "slow link" instead), but can also use normal pins to connect the chain. I through this is the chain I want to use, bought several and installed one on my bike without the "slow link" but with reinserting a pin. It failed during riding. I reinstalled it several times using a portable chain tool in my emergency tool kit but it all the time failed.

Then I looked at the pins. I found they had "punched" mushroom heads. So apparently the chain pin is not a good enough interference fit itself like chain pins were decades ago. Instead, the interference is practically nonexistent to make the pins fast to install during manufacturing, and then both sides of every pin are "punched" to make mushroom heads that force the pin in place. This is probably partially to save manufacturing costs, but also partially because apparently today bicyclists are unable to ease pedaling during shifting but rather shift during full load, and such shifts can damage a standard pin so apparently mushroom head pins are needed by today's cyclists (and before you ask whether I was shifting at full load when the chain broke, no I wasn't).

Such mushroom head pins get damaged if pushed out or reinstalled, and you can't therefore reuse them, not even if you don't fully push it out but leave it at the side plate to make it easy to reinstall it.

So the SRAM catalog either had outdated information (manufacturing process of the chain models was changed to "punch" pins) or alternatively had incorrect information.

Don't reuse pins today. Not on reinforced connecting pin chains like Shimano. Not on "slow link" chains like SRAM. You will get hurt. Several times, until you learn not to do that.

Today, I exclusively use Shimano chains. I pay some amount of money to have few spare reinforced pins on my emergency tool kit. I never clean and lubricate the chain off the bike. It works, but I would prefer chains with reusable pins.

At least on Shimano chains if I remove the chain the easiest way, with a chain tool (you can't disconnect a "slow link" without pliers if it's dirty because sand particles prevent you from opening it with finger force only), I can reinstall it with the same tool.

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To reset a loose pin with a chain tool, I used a bamboo skewer from the opposite side to stabilize the link and lead the pin into the hole.

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  • Hi, welcome to SF&F. I'm not sure I can picture exactly what you're suggesting by "opposite side." A diagram or photo would help improve this answer a lot.
    – DavidW
    May 10, 2022 at 19:13

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