Chain wear (again...)

[brussel]

OK so I have been giving this chain wear thing some thought especially after this mornings very muddy ride in Worcester.

 

 

 

I have a chain/cassette combo that according to accurate measurements is still within specs. But I put a new chain on and I get the chain skipping particularly in my most regularly ridden gear.

 

 

 

Someone here in a another thread made a suggestion that makes more and more sense to me.

 

 

 

Measuring pin to pin is only HALF the possible wear on a chain. It measures the wear on the INSIDE of the bush and pin interface only. So wear per bush x 12 links is the total wear.

 

 

 

BUT

 

 

 

The wear between the roller and the OUTSIDE of the bush is not measured (or if using a chain checker you can are actually measuring the wear on the inside of 12 bushes the plus the wear on the first and last rollers.

 

 

 

The most accurate way (I am thinking here...)to measure would to be to measure the the distance between two rollers separated by two pins:

 

 

 

 

that would give you the wear on the inside of two rollers AND two pins.

 

 

 

 

 

So what do you guru's think - or am I being overly complex?

 

 

 

I'm really trying to see why a chain that is within spec has worn a cluster to the point where it cannot be used with new chain.

[Windbreaker]

 

 

 

 

I have a chain/cassette combo that according to accurate measurements is still within specs.

Not accurate if your diagram is full picture. I think that you have the right idea but you need to measure a length of chain under slight tension so that the wear on individual links are summed.

 

The most accurate way (I am thinking here...)to measure would to be to measure the the distance between two rollers separated by two pins:

 

 

that would give you the wear on the inside of two rollers AND two pins.

 

 

Nope' date=' the wear on a single link will be too small to measure properly.

 

 

I'm really trying to see why a chain that is within spec has worn a cluster to the point where it cannot be used with new chain.

It doesn't sound like the chain was definitely within spec. But maybe I missed your point completely.

Windbreaker2009-06-27 11:00:29

[Bos]

Hey Bro, I recently experianced the exact same thing. Im a bit moeg to try and make out what you were on about the wearing and measuring part but! I wish there were some device that could log which gears we are using the most.. my worn out ring ended up being roughly 3rd from the bottom. I kept riding the chain and after about 150km on it(mostly in mud) and not using that worn cog much It seems its fine again.  So put the new chain on for a long ride or two and try avoid that gear.

Something else Ive been trying is to rather use my bigblade and use a bigger cog on the casette  as a pose to riding middleblade and in the 11 or 13t cogs at the back. The reasoning being that one use gears with more teeth which spreads the load and wear out over a bigger no of teeth.

Someone on here mentioned that he has 2 chains and swapps them between rides. Not such a bad Idea  huh. mabe every 100km or so.

Good luck

[brussel]

Windbreaker:

 

>>Nope, the wear on a single link will be too small to measure properly.

 

 

 

I agree - the theory is what I am testing - practically the tolerances are too small to accurately measure. If you took my measurement and multiplied it by 6 ( I think) you'd get combined wear on the links as well as the rollers - which I am wondering is not a better measurement?

 

 

 

 

 

>>It doesn't sound like the chain was definitely within spec. But maybe I missed your point completely.

 

 

 

It has less than 1/16 wear across 12 links. BUT there is a significant greater movement of the rollers compared to a new chain - so hence my discussion to see if the wear on the rollers is actually the issue

 

 

 

 

 

 

 

Bos: I have used three chains and have nearly 5000km on the three chains and cassette. I do clean the chains regularly to minimize wear.

[Johan Bornman]

The fact that your picture is wider than 600 pixels puts a burden on the reader. We have to scroll up and down and left and right in order to read the questions. I tried but now I have a hangover.

 

Proper chain measurement has been discussed here at length ('scuse the pun) and you'll find it easily. Search for chain elongation or such. Mampara did a nice sketch of how to measure the chain.

 

Bottom line is that ALL commercial chain checkers give an inaccurate reading and,  you say you measured the sprockets and claim they're still in spec. How did you do that?

 

Why do commercial chain checkers give inaccurate and inconsistent readings?

 

1) They measure too short a piece of chain and thus concentrate the reading instead of dilute them and

2) They invariably rely on a roller position. Rollers are floating elements in a chain and a dirty chain and clean chain will give two different readings.

 

Get a 12-inch ruler and stick to the imperial system, as abhorrent as it is.

 

Further, not only chain length (and thus pitch mismatch) wears out a sprocket, but grit on the chain can markedly sorten a sprocket's life - down to two chains.

 

Rotating two or more chains won't do anyting for sprocket life, it only simplifies your life in that you can soak the one whilst riding the other.

[brussel]

Johann sorry about the pic (and your headache!)

 

 

 

perhaps I was not entirely clear: I used a 12" ruler not a commercial chain checker to measure the chain. I cannot comment on the state of the cassette, only that if that chain was OK the cassette should also be?

 

 

 

I agree (mostly) with your statement about using two chains. In terms of wear and tear due to grit etc. using two chains would do nothing to lengthen a sprockets life. But if the wear is caused by a worn chain (stretched to use the common terminology) then the sprocket should last twice as long??

[Johan Bornman]

Ok, but then you measured a few links and extrapolated to 12 inches??

What is the total measurement over 24 links?

 

Rotating chains, where one or more of the chains are beyond its safe length will still wear the sprocket. Example, if you have two good and one bad chain and use the three over equat distances/terrain/conditions, then the sprocket would have worn 1/3 as much as it would have worn if you rotated three bad chains or kept just one bad chain on.

 

 

[splat]

[brussel]

I measured over a full 12 inches with a steel meter ruler. All 3 chains were within acceptable length (until I broke one of them - now I am down to two). I agree though if one is wrecked it will still damage the sprocket.

 

 

 

my suggestion is that to measure as I have suggested (if you could actually do it with any accuracy and repeatability) would be a better measurement than simply measuring across 12 links. Measuring across twelve links does not take into consideration the wear on the rollers...

[brussel]

Splat: both chains are at 1/16 inch elongation over twelve inches...and when I put a new chain on the cassette was worn enough to cause skipping...hence the whole original post. Perhaps our measurement does not take into account all of the wear on the chain and hence a chain that is still acceptable by the measurement you have shown above can still wear a cassette unacceptably.

[Johan Bornman]

Cut cut cut cut

 

 

Measuring across twelve links does not take into consideration the wear on the rollers...

 

Aha, I think I finally clicked.

 

Roller wear is irrelevant. You only need to concern yourself with pin/plate wear.

 

Read this...but take the day of first.

 

http://pardo.net/bike/pic/fail-004/000.html

[brussel]

OK Joahnn I think you're right a day off is need to process that...will get back to you

[brussel]

OK Johann,

 

 

 

I am an engineer and I am blessed to be able to read REAL fast

 

 

 

I can see why the current devices dont work well...and I can see again that roller wear is not as much of an issue as I might have thought.

 

 

 

But then how does a chain that is supposedly in spec still wear a sprocket enough to make it unusable...here is a pic just taken of the chain on the bike

 

[CaptainDura]

was that measured from the middle of the pin or the front of the pin.

 

if it was the front of the pin then that chain is outside of the norm and should have been replaced already a while ago.

 

[brussel]

CaptainDura - middle of pin - hence my frustration with the chain having worn the sprocket

[Johan Bornman]

Brussel, you're saying then (judging from the measurement), that the chain is still exactly 12 inches?