Why does a chain wear unevenly?

[Winston001]

Just discovered my chain is very tight in one spot - after I'd carefully adjusted it of course! I had adjusted until there was about 35 - 40mm play to allow for having raised the rear of the bike. In other words, slightly loose. Then turning the wheel I discovered the chain tightened up to no slack at all.

At the tight point, the chain appears to only partly fit on the rear sprocket. From about halfway around, it sits slightly out - not much but I can see the grease margins on the sprocket from where the sideplates normally sit. When turned to the loose position all links appear to sit in the teeth.

Why would a modern motorcycle chain stretch so unevenly? I don't know if this is the original chain - bike has 19,000km on it and I've had it since 9000k.

[McDuck]

Not lubed enough? Genrally somthing wrong, new chain time.

[cowboyz]

and sprockets. 20k out of a chain and sprockets is a little low but without regular (and by regular I mean the recommended 300k lube) it is not inconcievable. New chain and sprockets required.

[sinfull]

Not lubed enough? Genrally somthing wrong, new chain time.

Previous owner could have been wheelie mad or drag racing it ? Own up Winston !!!

Perhaps a light chain ?

But def time to get rid of it !

[awayatc]

my chain developed a tight spot as well....after only 7000 kms though....
Replaced it with one that hopefully lasts a bit longer....

[Winston001]

Hmmmm......this isn't very helpful team, no way I want to splash out for a new chain and sprockets.

I need a second opinion.

How about I reverse the chain......and do a few wheelies to balance out the tension....??

[xwhatsit]

Chains always seem to end up with `tight spots' (they're not really a tight spot though, are they, they're just unworn where the rest of the chain is worn, right?) and sometimes sticky links if there's a bit of corrosion. I'm not sure why they do that but it certainly seems to be the rule rather than the exception. Even my pricy O-ring chain has done that (I think they're probably worse once an O-ring or two wears out and lets the lube out and water/dirt in).

If the sprockets are fine, just do what I'm doing -- get a cheap heavy duty non-O-ring chain and use up the rest of the sprockets with that.

I don't think most people are worried about a tight spot on the chain though; the important thing is to adjust it for the tight spot, otherwise it'll be overtight in that one spot and do nasty things to the output shaft bearings.

I thought you were an old-school biker? You should know all about chains wearing out!

[Flip]

Chains always seem to fail like this. Water and corrosion seem to be the problem. I has a scott oiler on my 1200 Trophy and it did almost 50k on a chain and sprocket set.

[Ixion]

Chains always seem to end up with `tight spots' (they're not really a tight spot though, are they, they're just unworn where the rest of the chain is worn, right?) ..
I thought you were an old-school biker? You should know all about chains wearing out!

Correct. Chains don't develop tight spots they develop loose spots. The tight bits are the unworn bits.

Why do they wear unevenly? Who knows. Manufacturing variation in the hardness of components. Variation in lubrication and exposure to abrasive dust. The latte rmay be mor important, since fully enclosed chains (running in an oil or grease bath) both last more or less forever (except on pre unit Triumph primary drives ), and seem to wear very evenly
I think the Churchillian gentleman came from a BMW background.

[Winston001]

I thought you were an old-school biker? You should know all about chains wearing out!

Well yes. I still had a Duckhams chain bath under my bench until a couple of years ago. Shame I threw it out but it was leaking.

I think the Churchillian gentleman came from a BMW background.

Exactemont. Haven't had to think about chains for 20 years so bit of a learning curve here.

[Mental Trousers]

As pointed out, chains don't develop tight spots, it's just the rest of the chain gets loose from wear while the so called tight spot hasn't worn.
The reason chains wear unevenly is because they're made up of hundreds of parts that appear to be identical, but are all different on a level that we can't see. So, when subjected to repetitive movements a few million times they end up in different states.
Also, different links experience different conditions, ie 1 link may get some grit in it that others don't so it wears at a different rate.

[Winston001]

The reason chains wear unevenly is because they're made up of hundreds of parts that appear to be identical, but are all different on a level that we can't see. So, when subjected to repetitive movements a few million times they end up in different states.
Also, different links experience different conditions, ie 1 link may get some grit in it that others don't so it wears at a different rate.

Ah so this is a quantum thing. Cool. I get it now. Some of the chain is in another part of space/time and quantum fluctuations produce warps in the local area.

Well, that is certainly an eyeopener. Cheers.

[vifferman]

You're all talking shit.

Chains wear unevenly for two reasons:
Firstly, because of built-in bastardliness. If the manufactucturers built the wonderful, brilliantly manufactured, high-tech, super-duper chains they advertise, they'd last virtually forever. So they add a link or two here, and a roller there, and some wonky XYZ-rings there, that are bastards from the reject line. So your chain starts off looking all high-tech, shiny, gold-plated and wonderful, and gradually develops a personality of its own.
Secondly, they wear unevenly because no-one rides evenly. All that accelerating, wheelies, stoppies, riding over bumps, the swingarm pounding up and down, it acts in concert with the built-inbastardliness to fook the chain.
Thirdly, the bike and chain manufacturers pay the chain lube manufacturers to supply chain lube with secret ingredients such as abrasives, corrosion accelerators, and binding agents. They're all designed to produce a special grinding paste that's coloured red, so if you happen to go to a bike dealer, he can tell at a glance your chain is fookt, because it has red stuff on it.
Three-and-a-halfly, spooge. Chains are living organisms: they eat road spooge, drink chain lube, and shit out this nasty stuff called chain spooge. Stickier than the stickiest snot (which as we all know is gorilla snot), blacker and shittier than the blackest and shittiest black shit, in Nature it's designed as a fatal territorial marking to keep other chains away. Sadly, when the chain is captive on a bike, the chain spooge has nowhere to go but on the rider's leg, on the paintwork, and all over the chain itself, eventually causing PAMCFASITTRW (Premature And Messy Chain Failure And Serioius Injury To The Rider's Wallet).
Fourthly, misinformation about how to care for your chain. "WD40 will wreck your chain". "Use only motor oil". "Use only special chain lube" (with secret ingredients, of course).

All this has come about because chains are now fashion accessories. In the old days, they were hideously ugly, so they were hidden under clunky great chain guards, and never even thought about. Nowadays, you can get them anodised to match your bike or accessorise with your lingerie: gold, red, green, purple, or even leopard print. They all have fancy sexy names, and fancy 4-figure price tags, so you think you're buying into an exclusive chain-owners club. You feel good about your new acquisition, and about all the special chain care toiletries you're lavishing it with.
You scoff at owners of shaft-drive bikes, feel sorry for the poor guys with rubber band driven bikes, and smile your secret smile because you know they're not true motorcyclists who know how to clean and lube a chain, and become one with their machine. Those poor bastids!

[The Stranger:Me]

Hmmmm......this isn't very helpful team, no way I want to splash out for a new chain and sprockets.

I need a second opinion.

How about I reverse the chain......and do a few wheelies to balance out the tension....??

Just replace the fooken things.
19k isn't too bloody bad, stop being a tight arse.

What is the condition of the cush drive?
Not a common problem but the cush drive in the XT failed at 15k. The sprocket went all floppy, flogged out the carrier bearing, chain and sprockets. Shit happens, deal with it.

[Winston001]

Just replace the fooken things.
19k isn't too bloody bad, stop being a tight arse.

What is the condition of the cush drive?
Not a common problem but the cush drive in the XT failed at 15k. The sprocket went all floppy, flogged out the carrier bearing, chain and sprockets. Shit happens, deal with it.

Cush drive?? Sounds ghey to me. Ducatis don't have em.

But I could have a look I suppose.

Gents - a small confession. When I came back from the 4k North Island trip at New Year, there were various unsettling clunks from the chain south of Timaru. Being tired and heading into a night ride I said sod it and rode on......as you do. In hindsight I think the chain was so loose that it was riding up on the sprocket teeth now and then.

Bugger.