or

3) A crash or a chain dropping incident physically damaging a link.

I vote for manu defect or bad install, but whatever it is, it was a freak accident. Install the next one correctly and enjoy.

maybe the chain was just old(stretched)? no chain lasts forever after all. i hear a safe way to avoid this is by changing it every 6 mnths. and you don't need a Izumi super toughness either. a reg kmc should do fine

What about the teeth bashing back against the bushings when you engage the freewheel and are pounding up a hill?

The drive train will always be limited to whatever forces the legs can either produce or absorb.

like others have said, its either a bad chain, bad install, or both.

Thanks guys there's some interesting thought and debate going into this issue. Appreciate all your thought fodder, for sure. Though my original su*****ions if anything are slowly being confirmed amongst the noise - ie. my slackness with keeping the chain taught

Once again it was a relatively new KMC 'Z' 3/32" narrow chain; in the region of 600km (~ <400 miles) of life. It wasn't the master link that busted. Though it was only one link away from it (probably coincidence).

The photos illustrate that when it broke, the chain-ring threw the chain thereby also locking the drive-side crank at 9 o'clock as the slack was wound around the cog & hub locknuts. Also that the one remaining linkage plate at the break that wasn't lost shows that it was bent/torn outwards.

I wish I had my pics handy to post. I'm sorta trying to interpret what I can of the carnage myself - but experience from yourselves would of course be appreciated. I will post them from home tonight - in the a.m. US time.

pictures
 

A couple of pics as promised. Nothing too glorious; but hopefully something a with a little insight;

pic 1 : the whole shamozzle. How it locked up, how I came to a stop, how I carried the bike home and how I was able to take the photo ;)

pic 2 : the chain post mortem. though it's a bit dark, the master link is actually to the right of the shot.

pic 3 : the whole sorry mess of the chain & sprocket immediately before disection. note that the one loose end of the torn linkage shown in the previous shot is flipped up and gives you a better orientation.

That chain has clearly not been cared for.

rofl.. yah.. i doubt that a dirty chain is more likely to break, but damn, must be hard to pedal :)

Well, stiff links will obviously develop if its not cleaned/lubed. From the surface rust and wear shown on the inside of that link it clearly hasnt been taken care of.
He said it only had 400 miles on it.
It shouldnt look like that.

It looks like your chain was too slack, you threw your chain, and it broke while getting jammed between the hub & cog. It might not have broken if it were in better shape, but I think you would have had the same result at the bottom of that hill.

Take better care of your chain. At least look at it every week or so to see if it needs cleaning/lubing.

guys...i dont ever want this to happen to me... i dont want a mouth full of bloody chiclets.

how often do you lube, clean, align, etc...even how often should you change your chain?

It depends on how often you ride, if you ride in the rain, etc. Your chain needs lube when the sound if it going across your chainring and cog gets louder. Your chain needs cleaning if it looks really dirty, or if you can hear the grit in it.

Either get a chain cleaner like this one or take it off and shake it up in some simple green, kerosene, spirits or whatever else you use. Add your lube of choice conservatively -- I put 2 drops of oil on every roller, let dry, wipe off excess.

Your chain needs replacing when 12 links measure more than 12 1/8".

...and what is proper chain tension?

thnks littledjahn - I think you summed it up nicely.

I need to eat some humble pie about just how I well I assumed I was taking care of my chain. Being that the reactions to the pics thus far have that common theme. Whilst the outside faces of the linkage and their surface rust have bothered me... I was assuming that a few drops of white ligthning I have been giving it every coupla weeks was enough - obviously not enough. Some quick searches already reveal it's not necessarily the best lube anyway for my climate - not especially wet; but not especially dry either - which seems to be the ideal environment for the wax based lubes..

I think depending on the time of the year; I'll keep my faith in master links and rip the new chain off say, every other week and give it a thorough clean and also research a better; or at least more appropriate lube for my climate for top ups between cleans.

What I kinda hate about the topic of lubes is that most people seem to talk of particular brands. Often on this largely US based forum particular products or products aren't simply or readily available in Australia - or I get used to something and then my preferred/favourite LBS goes out of it and I have to face idiotic sales staff at other stores trying to sell me other crap when I am after something else specifically - which is why I got more into D.I.Y. in the first place.

Anyway.. with my old chain between my frame & cog and my tail between my legs... I'm off to search the other threads for little gems on the topic of chain care. I think the chain tension idea is now given. Lesson learned.

thanks guys...

3-4 parts mineral spirits to 1 part synthetic motor oil = prolink

This is probably the most dignified response I've read [on these forums] from someone who has been severely criticized. That took a lot of class; nicely done.

As tight as you can possibly make it without binding! One trick I've started using is similar to Sheldon's "Walking"...

1) Get the non-drive side in position and tighten it down so that the wheel is just slightly cocked away from the drive side.
2) Push/pull against the rim itself so that the chain is getting tight as hell. Use the whole wheel as a lever and the non-drive nut that you tightened is the pivot.
3) profit

Well, no, you don't profit, but I promise you can get the chain as tight as you want if you use that technique; and again, you want it is tight as you can make it without binding as you spin the crank.

Don't beat yourself up too much; everyone makes mistakes. Think of it this way; how many people have read this thread and have learned 2nd hand how important it is to keep you chain clean, lubed, and tight? You are a farkin hero man!

-Chry

maybe because he isn't an american?

//we suck

Mmmm... I like to think that I have some class, and I'm an American. I don't think as*holes are a strictly American export.

true true true.... i stand corrected....

Now this is interesting. I was wondering if there is a generic mixture of readily available products that give me the properties of a bicycle chain lube. Similar to buying a lead additive for an older car fuel - or mixing up a 25:1 Fuel to Oil mixture for a two-stroke lawn mower or yard trimmer.

Avoiding more expensive brand names not necessarily always available to me is an attractive option.
If I'm going to the trouble of regularly getting grubby cleaning a chain - surely the extra effort of mixing up a lube concoction every once in a while is surely of neglible extra hassle.

Do any/many forum readers mix their own ?

I've used chainsaw bar oil for my chains for years. The only real difference between that and Phil Tenacious oil is that the bar oil is colored pink.

I don't know if you have a saw shop close, but you can usually get a quart for ~$3 from Home Depot.

i got that far.

all you have to do is get a 1/8th, and you'll never break a chain again.

I used to mix up my own, thinning chainsaw chain & bar lube with a lighter oil. Once Phil Wood Tenacious Oil became available, I stopped bothering with this.

Not only is Phil the best chain lube I've ever used, it is also the very first to come in a container that seals well enough to carry in a bike bag without worrying about leakage ruining the bag!

Sheldon "Philophile" Brown