Hello,
Well during my commute in this morning, the chain broke. I have purchased a replacement chain from a nearby bike store. This KMC chain comes with this type of quick release...



Will it work with my 21 speed deraillers?
Will it get me home?

If the shop looked at your chain that broke, then it should fit fine. As long as the two ends of the chain are ready for this link to be inserted in them to hold the chain together.

Panthers, it is a brand new replacement chain set. I didn't bring the bike to the store as I locked it in the office.
I am concern if it will break the RD or not. Also it has a total of 112 links. I don't even know if it is too long or too short. I just need to install it and somehow get home. I have no tools.

Compare the length of the old chain to the length of the new chain and find out how many extra links you have. You should be able to get away with about 2-3 extra links but you will still run the risk of it slipping off if your not careful.

Try not to use the front granny and stick to your biggest gear (high gear). Meanwhile the rear derailleur should be able to manage the slack on everything other then the highest gears (smallest).

The other thing you could do is take the old chain to the bike shop if it's near by and have them size it quickly for you and pop off the extra links.

As for the quick link it's fine to use it and will work with any drivetrain as far as my understanding goes. Never heard of anyone running into too many problems with them aside from some complaints that certain makes will wear down faster then others. Their mainly used to help in maintenance of the chain or to work on the drive train. It allows for quick removal and prevents premature wear on the rivets caused by chain removal tools.

^thanks for the tips! Well I installed it. This clip version of the quick release link makes it easy to install. Thought I needed pliers as per instructions. But I was able to pop it in with my keys. I didn't mess with the length for obvious reason that I didn't bring tools. Will carefully ride back and take a closer examination in the comfort of my garage.

These should help you to learn about chains-tools and chain-links:

https://bicycletutor.com/quick-release-chain-link/

and...

https://bicycletutor.com/chain-tool/

Also see the Park Tool repair site:

https://www.parktool.com/repair/

^ yeah I've gone through them already. Interesting, bicycletutor seems to indicate that the chain link I posted is for fixie bikes. Anyhow I manage to ride home safely. It shifted a bit weird. Was rubbing the FR cage. Adjusted cable tension via the barrel knobby. Works fine now. Also checked for chain length. Seems to be find. It has the S-bend in all gears that was depicted at Parktool's site. Think I am good to go for tomorrow.

While the best indicator that the chain is long enough most times is a nice S pattern in the rear derailleur is is still best to re-size the new chain using the old chain as a guide.

Reason for this is even though the chain may appear to be sitting on the gears correctly. It could still provide some issues when shifting into certain gear combinations by there being too much slack in the chain.

If you want there is a really good alternative method of sizing a new chain taught via bicycletutor at https://bicycletutor.com/calculate-chain-length/. Though even he still recommends replicating the same length as the old chain if you still have it.

As for chain tools if you don't have one already they are dirt cheap as most LBS's and shouldn't cost you more then $5. Even though you don't need one after you've sized the chain and have a quick link they are still nice to have in your tool box just in case.

Looks like bought a single speed chain. That is a three piece connector used mostly on kids bikes and beach cruisers.

+1
Looks kinda wide for a derailleur chain link.

Looks like 1/8 chain to me... that won't work with a cassette or freewheel.

5-6-7 speed chain is usually interchangeable while 8, 9, and 10 speed chains are more specific... 9 and ten speed chain is very narrow at the outer plate and the pins are flush to give it enough clearance on a narrowly spaced cassette.

^ Huh? really? I didn't even read the packaging. It is a 7speed cassette FWIW. It shifts fine. I even rode >35km back home yesterday. Should I return it then?
Mind you the image I posted is just a random sample image I got from the web. Not the actual link of the chain that I have. It is for reference purposes.

Your LBS wouldn't have sold you the wrong chain unless they really didn't have a clue about bikes which is doubtful.

Your right on your assumption that they only saw the picture and not the watermark indicating it came from a site for scooter parts Even I figured out that you were using it as a reference photo vs. a photo of the real component

So don't worry about it you've got the right chain for your bicycle and it appears to be working for you. But, I still suggest checking the length using the two methods I previously posted if you haven't already.

Well truth be told, I didn't bother asking. I just grab the chainset pack and paid. Off i went. I didn't know that there's differences in chains. Yikes! It's only a bicycle.... or so I thought.
However to think about it further, I do notice that the chain now rubs against the FD cage on some gear combos. None before.

Better do some reading up on chains. There are quite a few varieties on the loose. Mostly for different gearing. Some for 1/8-inch cranks and cogs as found on 3-speeds and BMX. Most are 3/32nds for derailleur bikes - but different models for 5,6,7,8-speed cassettes/freewheels. 9 and 10 each take a different animal. And Campy has their bloody 11-speed one out there.

so what's these 3/32 and 1/8" are they width? thickness? what does it measure?


OK did some research. it refers to the inner width of the chain. I guess the 1/8" width is for fixie and 3speeds where the cogs are spaced wider? Hmm.... I better go check the packaging again. I may have to switch it for a 3/32". Hopefully the LBS is cool with it.

1/8 chain would not work with a 7 speed so you probably grabbed the right chain... some very old derailer and freewheel combinations can handle 1/8 chain.

There are 3 sizes of chain in use for bicycles... 3/32 (for derailer gears), 1/8 (for singlespeed, 3 speed, track), and 3/16 which is used on heavy duty utility bicycles.

As stated, there are quite a few varieties of 3/32 chain for different speed cassettes and there are some small variations between the outer plate width on the same sized chain with different manufacturers.

SRAM chains tend to run a little narrower and are also the standard by which I measure chain quality as they tend to be very consistent and reliable.

Fixed drives come in 1/8 and 3/32 and the 1/8 cog is actually thicker as are the chain rings to add strength and also to reduce wear... there is no cog spacing on a monospeed bike to worry about.

Most English 3 speeds like a Sturmey Archer typically use 1/8 drives while Shimano 3 speeds use a 3/32 drive... coaster bikes typically use 1/8 drives.

Oh noes! I just checked the packaging and it reads 1/2 X 1/8"!!! Crikeys! I hope I didn't damage the gears. I've been riding it for the past 2 days including a >35km trek home yesterday! Seems to spin fine. It did rattle abit with the FD cage. Should I switch it out for a 3/32?

Does that mean I have an old derailer? The bike's only 3 yrs old!

Just an update for closure sake...

I replaced the 1/8" chain with a 3/32" chain. During the removal of the 1/8 chain, I can easily now see the width of this chain type and was able to wiggle freely b/t the chain and the gear tooth. While with the 3/32, the fit was better. Does not have as much wiggle space. And that also solved the rattling issue with the FD. This is because the wider 1/8 was touching the wall of the FD cage while the 3/32 has a tighter tolerance fit.
So all is well again. Thanks everyone!