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Chain link has begun to seperate - causes chain to hop off gears

New poster here, but been visiting the forums a bit, always learning something new.

I've run into a problem with the chain on my old 70-80's Peugeot road bike. One of the links appears to have started to separate as shown here:
I believe this causes a problem when I am creating lots of tension on the chain and it approaches the top of the front cogs. Due to the angle between the front gears and the chain, sometimes the little side gap on the link gets caught on the cog tooth, and the chain pops off the ring - usually leaving me with a sore spot and a few frustrated comments.
It's hard to verify exactly what's happening because it usually only occurs when the bike is being ridden - when i'm just turning the crank by hand, it hasn't occurred...yet. It's definitely getting worse more recently. Last week I went out and the chain came off 3 times in 100m.

I'm tempted to have a the link with a pair of pliers, but I don't want to end up with a stuck link.

Other options I'm considering are:
1. replacing the chain - I have no idea if that's a good idea (given I have no intention of changing the gears).
2. buying a snap on replacement link (lbs recommended this as a $5 fix option)

I don't have a chain tool, but it looks like either of these options may result in me getting one Tongue

Wondering if the experts (an non-experts) on this forum can offer any input.

Many thanks!
Either option would work. Up to you which one you are more comfortable with. Personally, I would go with the new chain. Hard to believe that you would not be changing gears at some point.
I agree. A new chain would be the best bet. Also, I wouldn't ride it very hard or far with the chain in that condition. Wait till you get a new chain or repair this one.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Daily
definitely new chain.

how did you get the chain so clean - that could be part of the cause of early failure......
The pins on that link look longer than the ones in the other links. Maybe the chain was incorrectly assembled when it was put on the bike and it took this long for the link plate to migrate out to the notches? I'm assuming your freewheel only has 7 gears on it, so a replacement chain wouldn't be much more in cost than the $5 master link. Get the link, too, and then it'll be easier to take the chain off for cleaning Big Grin
Thanks for all your responses - I will probably start looking into a new chain. That said, I'm not 100% if this link is the reason why the chain falls off.

I stopped by a LBS and showed one of the mechanics my photo. He suggested a new link, and some snapon link thing, but he also mentioned just using a pair of pliers on it to tighten them back up.
Naturally, i went with the easiest & cheapest approach first and had at it with a pair of pliers. Unfortunately upon taking it out for a test drive, and while putting a little pressure the chain, it still fell off the the inner cog on the front gear. Unfortunately, I still can't reproduce this problem off the bike...

The problem only seems to happen while I'm using the smaller front cog, and largest rear gear. When I'm using the middle rear, it doesn't fall off. So basically it's only a problem when I'm going up something steep...

dave_sd - yeah, the links do look strangely longer. I noticed that as well while staring at the thing. The freewheel has actually only 5 gears (it's a 10 speed)

nfmisso - interesting point. I did start having this problem more after I cleaned the chain pretty vigorously. The bike has been in storage for many years, and I figured I'd give it a nice cleaning before taking it out again. I recently started "restoring" this bike. New tires, new brake shoes and i swapped the dropped handles to a flat bar (the dropped posture was uncomfortable).

Thanks again for everyone's input
I would not clean the chain "vigorously" as that removes the grease installed at the factory, that there is no way to replace. Just wipe the exterior with a rag (old cotton underwear) and lightly oil from the inside of the loop, then lightly wipe off with another rag. Do it every 500 miles, and the chain will last.
Well, after having stored the bike for several years even the factory lube will be bad (I guess). So cleaning the chain actually is an option. However, chain cleaning is a subject discussed with almost religion-quality stubbornness (no offense meant to anyone, I am not a native speaker and stuff), so I won't open that can of worms (again). Nigel's tips are (also in my opinion) the way to do it if you ride in clean and dry conditions only. I do cross duathlons which involved riding in knee deep mud (or snow), so I do run the chain through a cleaning tool. Clean(ish) chain is better than one that sounds like a coffee grinder...

On to the actual problem, assuming everything else is set up correctly and the dérailleur hanger is not bent: You should replace at least chain and freewheel (a 6 speed narrow one might _just_ fit the hub). The description sounds like worn chain + sprockets. Then, the crank set (well, the chain rings) might need replacement, too. Fortunately there are still some companies that offer square taper road bike crank sets (might be cheaper to get one of those instead of chain rings). If the crank set does not fit (axle length...) get a crank set that has the same bolt circle diameter as the old one and swap the chain rings. Other option: reverse the chain rings (take them off, flip 'round, put on). On old bikes this should work (on new ones they have a special geometry to allow the chain to climb better, reversing chain rings will decrease shifting performance there).

above is a link to a new 5 speed freewheel.

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