How safe is adding chain links back regarding weakness?

[Manc33]

Its always a weaker link adding a piece back I guess but, is it "stupid" to?

I remember once looking at my chain and a link was breaking apart, yup it was a rejoined chain. That time I can't say I rejoined it well enough.

This time I joined a piece and the join felt right when I pushed the pin back in. I just wonder how often they do come apart. I have rejoined loads and only ever had one do that.

Its vital to get the pin equal on each side and the roller loose as far as the chain will bend, which it is in this case. It went back together better than they usually do but, its a KMC X9-93 (god tier chains to me compared to S or S lol)

[Brucey]

if you look at the parts under a microscope (or a strong magnifying glass) it is evident that the pin swaging (that allows modern chains to be abused) is largely lost. What you can't see easily is if the holes in the side plates have also been opened up or not (they usually have).

If you want a simple test, experiment with a length of chain and try pushing the same pin out the same way for a second time; the force will usually be tiny by comparison with the first time. The chances of that link popping open when you are running cross-chained or are making a loaded shift are pretty good. Obviously both of those events are much more likely to happen on a well-used MTB than (say) a touring bike.

If you believe that the pins only lose their swaging (and that the side plates are still OK) then you could consider re-swaging the pins. Again you could demonstrate that this works by experimenting with some spare links, and seeing if the pin pushout force can be restored or not.

In general as well as the type of use it will see, it becomes an even more daft thing to do when the chain gets narrower; so what might be OK on an 8s touring bike chain (or in an emergency) gets progressively worse as you go to 9s or 10s and none of it is a terrribly good idea on an MTB IME.

cheers

[mattsccm]

I guess I was in 8 speed territory before I discovered quick links so up to 8 I always rejoined with a tool and never broker one. 9 and up and it has always been the quick version which have never failed me. Some chains have 2 in and one had 3.

[reohn2]

I always use Powerlinks(Sram) Missinglinks(KMC)to join a chain,they're not expensive and I've never had on fail.It's a no brainer for me.

[Mick F]

I always use Powerlinks(Sram) Missinglinks(KMC)to join a chain,they're not expensive and I've never had on fail.It's a no brainer for me.

I tend to agree with you, but I have a couple of stories.

1. Campag C9 chains, I had a couple of them when I was in 9sp guise, and regularly split and joined the chain. I reckoned that the odds on me getting the same pin were 114 to 1 so I felt safe. Never had an issue. All was fine.
I joined this forum at about that time 2004? and learned that KMC Missing Links existed. CJ put me on to them, so I bought one and my life became easier.

2. Campag C10 chains, I've had four or five of them over the years, and now have one and one spare for Mercian and one and one spare for Moulton. KMC MLs on them all.
One day, riding Mercian, I lost my chain. Luckily, I was only three miles from home so I walked and freewheeled and scooted home to fit a spare to go and find it.
It was undamaged, but the KMC Missing Link was ......... er ....... missing.

[reohn2]

I must admit the KMC m/link is only on one new bike(Genesis Longitude MTB) that came with a KMC 10sp chain fitted and so far is still on the original chain and link only being removed and refitted for cleaning.Sram Power links(8 and 9sp) OTOH I've been using for donkeys on solos and tandems both for final drive and timing chains without a single failure that I can recall,and I uss the same P/link for the life of the chain

[531colin]

Its always a weaker link adding a piece back I guess but, is it "stupid" to? ........

Its fine with a "magic link"

[Manc33]

Cheers folks. I suppose the best bet is a new full chain but I'll ride it and see.

Brucey yes there's usually a really thin ring of metal comes off when taking a pin out and its twice as hard to push a new pin out than one already done, because of that lip/ring of metal.

Thinking back I reckon the one that did start coming apart had been split twice at the same place, its possible with the amount of tinkering I do.

[Brucey]

chains have pins that (in the simplest terms) are either partially swaged (most 7/8s chains) or (in some 9s, most 10s etc) they are swaged over the full circumference, into a slight recess in the chain sideplate. The latter is often called flush riveting or bullseye riveting. The partial swaging usually puts some small facets or flats on the end of the pin.

If you see a continuous ring of metal come out of the joint in a chain with flush riveting, it could have come from the pin or the side plate. If you see a ring come out of a chain with partial swaging on the pins, it is most likely that the metal has come from the side plate.

In some 8s chains when the pin is pushed through, the swaged lumps are knocked off the sides of the pin and the side plate is not that badly damaged. You don't tend to see rings of material produced in chains of this type. In theory if you can re-swage the ends of pins you might get the chain back up to a reasonable strength. But if the side plate is damaged enough, nothing you do with the original rivet will restore the strength of the chain.

Many chains use a special 'joining pin'. This is oversize (differently at each end) and may have ridges on it too. This is intended to accommodate damage in the side plate, and may 'resize' the hole in the sideplate on its way through. This is better than pushing the original pin back into the hole and hoping for the best, but it has always seemed a bit hit and miss to me.

Quicklinks vary in their fit, such that some come apart very easily, and others definitely snap together such that they won't easily come apart again. In theory re-usable ones are the first sort and non-reusable ones are the second sort, but in reality some links that are reusable are difficult to take apart, and other links that are meant to be non-reusable can sometimes be re-used.

cheers

[Des49]

I have a Rohloff chain tool with which you can peen over the pin ends after re-riveting. However even with that on modern chains that use a quicklink, as already mentioned, that ring of metal is pushed out when pushing out a pin and this must weaken the link, so then I use quicklink only and carry a spare quicklink in the on bike tool kit.

[Manc33]

So use a quick link even if you end up with 2. Thats useful because you can swap between cassettes (or, rear wheels if you cannot be bothered taking cassettes on and off). Mechs exist to do that, the Saint M810 can be swapped from 23t low to 34t low with a piece that screws on the mech. That mech, 2 rear wheels and the chain piece and you can swap from mountain cassette to road very easily. Its a bummer that the Saint is only a GS and not a SGS, or you can fit the M972 cage thats SGS but carbon (and a stupid price).

Or you can do the other thing and buy another derailleur hanger the same as your current and cut a bit off one of them, thats the one for 23t sprocket. All the Saint does to swap between 23t/34t is do that exact same thing.

[Mick F]

So use a quick link even if you end up with 2.

On my Moulton, I need 116 links.

I use a Campag chain, and they come as 114 links, but the 114th is a special one that I take off. This means that I have 113 links starting and ending with an inner link. By adding a KMC Missing Link plus a spare inner link, then a second KMC ML, it makes 116 links.

[The utility cyclist]

if you look at the parts under a microscope (or a strong magnifying glass) it is evident that the pin swaging (that allows modern chains to be abused) is largely lost. What you can't see easily is if the holes in the side plates have also been opened up or not (they usually have).

If you want a simple test, experiment with a length of chain and try pushing the same pin out the same way for a second time; the force will usually be tiny by comparison with the first time. The chances of that link popping open when you are running cross-chained or are making a loaded shift are pretty good. Obviously both of those events are much more likely to happen on a well-used MTB than (say) a touring bike.

If you believe that the pins only lose their swaging (and that the side plates are still OK) then you could consider re-swaging the pins. Again you could demonstrate that this works by experimenting with some spare links, and seeing if the pin pushout force can be restored or not.

In general as well as the type of use it will see, it becomes an even more daft thing to do when the chain gets narrower; so what might be OK on an 8s touring bike chain (or in an emergency) gets progressively worse as you go to 9s or 10s and none of it is a terrribly good idea on an MTB IME.

cheers

How often is "pretty good" in statistical terms, once a week, once a month, every 50 miles, every 250, 500?

Have fitted 5 excess links from another bike to a new chain that was shortened but not used - 6700/Ultegra chain 5 lightweight 'gold' YBN links, that's 10 speed. It cost me £6.70 posted for the (new) 6700 due to it being shortened.
I can't say I had any issue with it on the daily that gets used in all weathers and extreme duress (100kg rider + 20kg load + bike/bags etc up 8% on occasion), it's done circa 600 miles so far.

[NATURAL ANKLING]

Hi,
Up to and incl 8 speed is pretty reliable if you trust your ability to get it even and use judgment in how tight the fit is, PLUS never split chain using same pin twice!

One of the most difficult things to get right if you don't want failures, I will still rather join a chain this way than a q link.
But if the pin is easy to fit then it will be less reliable.
Shimano do supply a solid plain pin part assembled on some of their chains, but any loose pins I don't like or use.

Mick F has said in the past that the Q link idea will produce slack in the pin clearance, probably with reuse.

[pwa]

I've had a couple of link breakages over the years, and as a consequence I now have a SRAM Quick Link and a multitool with a chain tool on it, permanently in my small pack for on-the-road fixes. In theory, if a chain breaks (and I don't fall badly as a result) I will be up and going again in a few minutes. If it happens I will let you all know whether theory and reality turn out the same.

So far, carrying a Quick Link has only helped someone else I was riding alongside, who had a broken chain and benefited from my own spare Quick Link. He was lucky to be using a 9 speed chain like mine.