Chainwheel, Chain and Cassette Worn But Why Replace

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greyingbeard
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby greyingbeard » 7 Jan 2016, 4:46pm

Someone will correct me if Im wrong
The "accepted" wear limit for a chain is a measured stretch of 1/16 of an inch over a foot.
Chain pieces are 1/2" apart so you get real units of measurement. A metal rule is all thats required.
Replace the chain when it gets to the limit ish and cog wear wil be minimal.

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Mick F
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Mick F » 7 Jan 2016, 5:07pm

greyingbeard wrote:Replace the chain when it gets to the limit ish and cog wear wil be minimal.
Even if you used a brand new chain every time you rode your bike, the cogs would still wear.

I was horrified when I put on a new chain and my small cog jumped. I'd changed my chains regularly (I have three or four) and none of them ever got beyond 1/6th inch over the whole of my 39" steel rule!

The cassette was renewed at 6,528miles because a new chain jumped on the small cog. The rest of the cogs were fine.
Knowing what I know now, I'll buy a separate 12t cog ..................... at perhaps £20+ next time.
Mick F. Cornwall

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Chris Jeggo
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Chris Jeggo » 7 Jan 2016, 5:39pm

1/16 of an inch in one foot is one part in 16x12=192, i.e. 0.5%.

My Park Tools chain wear gauge is a two-sided go/no-go gauge, that is, one side tells you whether or not the "wear" exceeds 0.75% and the other side tells you whether or not the "wear" exceeds 1%. What it actually measures is (a) the wear between pins and bushes, plus (b) the slop between rollers and bushes (and there's always some of that). What you actually want to measure is (a), hence a ruler is the thing to use.

The "accepted" wear limit is 0.5% for some people, more for others.

My experience is that replacing a chain when the wear is far less than 0.5% still results in some chain skipping. I thought I would make a freewheel block last two chains (this was before cassettes were invented). After new chain A had run for 500 miles on a new block I removed it for thorough cleaning and re-lubricating and fitted new chain B. Some skipping occurred on the most-used sprockets, but reduced to nothing over the next 100 miles or so. After chain B had run for 500 miles I removed it for a clean & lube and re-fitted chain A. Some skipping occurred ... as before. I kept repeating this process until everything wore out, and the behaviour kept repeating itself likewise. I never repeated this chain rotation because (1) although the skipping was not bad, I did not like it, and (2) I spent hours removing, cleaning and refitting chains. I have no record of, nor memory of, measuring the wear after the first 500 miles, but I estimate that it must have been so small that it would have been extremely difficult to do so using a ruler.

So my experience, and that of some of my friends, is that chain rotation does not work. Some people say that chain rotation does work if wear is less than 0.5% but I find that hard to believe. Other people say merely that chain rotation works without saying how they get it to work. Maybe they spend a lot of time keeping everything spotless, but I prefer to spend most of my time riding my bike rather than cleaning it.

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Mick F
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Mick F » 7 Jan 2016, 5:44pm

Chris Jeggo wrote:So my experience, and that of some of my friends, is that chain rotation does not work.
No it doesn't.
I expected it to, and I did it religiously, but the small cog on my cassette still wore.

Things wear. You cant stop them.
Mick F. Cornwall

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Chris Jeggo
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Chris Jeggo » 7 Jan 2016, 5:48pm

Mick F wrote:... none of them ever got beyond 1/6th inch over the whole of my 39" steel rule!


That's 0.4%. We are in good agreement.

Psamathe
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Psamathe » 7 Jan 2016, 6:15pm

Chris Jeggo wrote:1/16 of an inch in one foot is one part in 16x12=192, i.e. 0.5%.

My Park Tools chain wear gauge is a two-sided go/no-go gauge, that is, one side tells you whether or not the "wear" exceeds 0.75% and the other side tells you whether or not the "wear" exceeds 1%. What it actually measures is (a) the wear between pins and bushes, plus (b) the slop between rollers and bushes (and there's always some of that). What you actually want to measure is (a), hence a ruler is the thing to use.

The "accepted" wear limit is 0.5% for some people, more for others.

My experience is that replacing a chain when the wear is far less than 0.5% still results in some chain skipping. I thought I would make a freewheel block last two chains (this was before cassettes were invented). After new chain A had run for 500 miles on a new block I removed it for thorough cleaning and re-lubricating and fitted new chain B. Some skipping occurred on the most-used sprockets, but reduced to nothing over the next 100 miles or so. After chain B had run for 500 miles I removed it for a clean & lube and re-fitted chain A. Some skipping occurred ... as before. I kept repeating this process until everything wore out, and the behaviour kept repeating itself likewise. I never repeated this chain rotation because (1) although the skipping was not bad, I did not like it, and (2) I spent hours removing, cleaning and refitting chains. I have no record of, nor memory of, measuring the wear after the first 500 miles, but I estimate that it must have been so small that it would have been extremely difficult to do so using a ruler.

So my experience, and that of some of my friends, is that chain rotation does not work. Some people say that chain rotation does work if wear is less than 0.5% but I find that hard to believe. Other people say merely that chain rotation works without saying how they get it to work. Maybe they spend a lot of time keeping everything spotless, but I prefer to spend most of my time riding my bike rather than cleaning it.

About 3500 miles ago my chain was replaced. Perviously I'd been alternating between two chains each with around 2500 miles on a new cassette. when chain replaced (i.e. on a cassette used for 5000 miles), shop thought cassette was just ok. It skipped a bit but shop said it should settle down within a week and it did. (I like it when shop tries to avoid pushing new bits on you when you don't need them).

However, when I was swapping/alternating the two (identical) chains (not that often) I never had any slipping.

Ian

Psamathe
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Psamathe » 7 Jan 2016, 6:17pm

Mick F wrote:
Chris Jeggo wrote:So my experience, and that of some of my friends, is that chain rotation does not work.
No it doesn't.
I expected it to, and I did it religiously, but the small cog on my cassette still wore.

Things wear. You cant stop them.

When I was alternating chains it was as much to give more time for the cleaned chain to properly dry out (i.e. all the water to dry out of around all the rollers/pins) so that the lube would then get in properly. So more for convenience than wear.

However, when they were replaced I felt a bit broke so only purchased a single chain.

Ian

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Mick F
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Mick F » 7 Jan 2016, 6:26pm

Yep.
That's the way I was. One chain on, one in the wash. I had one spare too.

It doesn't work.
Yes, it means you can keep your transmission clean ......... and I still do it like that.
What it doesn't do, is allow things to last longer.

The cassette needs to be replaced no matter how many clean chains you use.
As I said, you can use a brand new chain every single day, but the cogs will still wear.
Mick F. Cornwall

reohn2
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby reohn2 » 7 Jan 2016, 6:34pm

Chris Jeggo wrote:....... Maybe they spend a lot of time keeping everything spotless, but I prefer to spend most of my time riding my bike rather than cleaning it.


It take me 15 minutes max to clean a really mucky drivetrain,how far can you get in 15 minutes :wink:

If I keep on top of the cleaning,I usually get 4k+ out of a 9sp Sram 971 chain(£10) when it's @ 1/16th over 2ft it's replaced,I usually get through three chains before the cassette skips.
My 8sp cassettes are hybrid 14-32's made up from two 9sp cassettes (with 8sp spacers), a 14-25 Tiagra and a 11-32 HG something(Usually £20 for both).
Which amounts to £50 for 9 to 12k miles,I'm happy :D
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Brucey
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Brucey » 7 Jan 2016, 6:44pm

Chris Jeggo wrote: ....My experience is that replacing a chain when the wear is far less than 0.5% still results in some chain skipping. I thought I would make a freewheel block last two chains (this was before cassettes were invented).


I think you mean 'popular' rather than 'invented', unless you were doing this in the 1920s.... :wink:

After new chain A had run for 500 miles on a new block I removed it for thorough cleaning and re-lubricating and fitted new chain B. Some skipping occurred on the most-used sprockets, but reduced to nothing over the next 100 miles or so. After chain B had run for 500 miles I removed it for a clean & lube and re-fitted chain A. Some skipping occurred ... as before. I kept repeating this process until everything wore out, and the behaviour kept repeating itself likewise.....

So my experience, and that of some of my friends, is that chain rotation does not work. Some people say that chain rotation does work if wear is less than 0.5% but I find that hard to believe. Other people say merely that chain rotation works without saying how they get it to work. Maybe they spend a lot of time keeping everything spotless, but I prefer to spend most of my time riding my bike rather than cleaning it.


It is as well to realise what is going on here; there are essentially two wear processes at work

1) wear in the loaded part of the tooth, when the chain is under load (this makes the tooth form look hooked) and

2) wear in the part of the tooth that the chain roller slides over as the chain engages with the sprocket (this counteracts the hooking wear).

In a nutshell if there is lots of the former and not enough of the latter on any one sprocket then the 'new chain' will skip. It skips mainly because the 'new pitch' is short enough that the chain won't engage smoothly with the sprocket .

There are things that make skipping more likely when you rotate chains;

- a full tooth form on the sprockets; (modern cassettes have a truncated tooth form so that you don't need much type 2 wear to keep the chain from skipping)

- a short chain wrap round on the sprockets

- soft sprockets

- chain rollers without much slack in them (slack rollers give more type 2 wear)

- much heavier wear on a few sprockets than others (eg through some being very favoured)

- low chain tension from the rear mech.

- use of small sprockets rather than large ones

- ineffective chain roller lubricant

- high chain tension (from pedalling)

So I think you are less likely to be able to rotate chains without jumping on some older style freewheels; in addition there may be several other factors at work.

I also think that Mick's 12T sprocket was the odd one in the set (with an integral spacer) so may have been made in softer steel than the others. [Shimano ones are certainly like that.]

There is a complication in that even if a worn sprocket doesn't have a pronounced hook to it, it may have enough shape to the valley part of the tooth that the 'new chain' will (for a while) try to ride up the teeth slightly whenever the chain tension is high. This can provoke skipping too, even if the sprocket doesn't look that hooked. This behaviour normally goes away after a short period of use.

In theory if a 0.5% difference in chain length can provoke a skip, you are looking at a clash of no more than 0.0025" on each tooth, which is about 64 microns. If you can remove that 64 microns, or wait for it to happen naturally, then you ought to be able to rotate chains quite happily. Most people find that they can rotate chains OK on modern cassettes; by contrast I've had the worst skipping on freewheels with full-height teeth.

BTW Rohloff sell a tool that looks a little like a chain whip that allows you to assess if a given sprocket is going to cause a skip or not; chain is wrapped round the sprocket and tensioned in the drive direction; if it doesn't engage/disengage from the sprocket easily in the right place then the sprocket is worn enough to cause trouble. You can make the same assessment yourself provided you can do something similar using the chain you intend to use.

cheers
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mattsccm
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby mattsccm » 7 Jan 2016, 9:26pm

If the chainrings are really knackered, and they will go for ever when it that states, I would just run it till its dies. Especially over the winter. My gravel bike gets the cast off from my road bike as it gets plastered in gravelly mud 5 days a week. I keep everything going until it just won't shift. It seems to die about once a years, that's about 4000 miles and the road bike then donates a nice useable chain and sprocket set that's done about the same or less but on the road. I am still using up a selection of old chain rings as well. It works out at a chain and cassette every year and chain rings every other. They tend to be alloy MTB rings . I just hate to abuse new chains in all that gravel slurry.

jb
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby jb » 7 Jan 2016, 10:23pm

I rotate 3 chains at 500 miles on my light day bike and never had a problem, yet. I think a lot depends on what sprockets you tend to use most. Some people seem to stay in the smaller sprockets and change on the front a lot, where as my smallest sprocket is hardly used.

Roller wear will contribute to chain mismatch as the pins are lower and thus out of sink with the sprocket pitch so I think the Park tool measuring both pin wear and roller clearance is not a bad idea IMHO. but there are so many variables in chain use that its difficult to get reliable data and thus form an opinion that's useful to anyone but yourself.

In the days of friction shifters we would generally change the chain when it was noticed that a roller or two were missing; then with a new block & chain it would usually run on the chain rings for several of these changes before slipping occurred. but the older systems had more fully formed teeth & didn't snake so much.

These days I like a quiet nice running chain on my good bikes so they get changed at not much over 1% .
Cheers
J Bro

PH
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby PH » 7 Jan 2016, 11:37pm

My most used derailleur bike is on around 6,000 miles (Over three years) without changing anything and is just starting to skip a beat now and then. I've had a new chain, Campag cassette and middle ring ready to go on since last winter, cost was around £40. Chain gets a wipe when it's mucky and some Wilko's oil when it's dry, nothing wrong with people taking a pride in having a shiny bike, but I'd need some convincing that there's a financial or mechanical advantage.

Des49
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby Des49 » 8 Jan 2016, 12:34am

My daughter's 14-25 10sp junior cassette on her racing bike cost over £50, plus they can be very tricky to find. I am more than happy to change the chain well early to prolong the life of the cassette.

My racing bike, with it's 28 yr old Dura-Ace transmission is still on the original sprockets. OK it's not used much nowadays, but I used to change the chains at the minimum twice a year to ensure the transmission remainded unworn. Mind you that was in the day when we could buy a bag of several loose Sedis chains for a fiver, modern 10 and 11 sp set ups need far more expensive chains so things become a more delicate balancing act between maxmising chain life and catching sprocket wear just in time. I shudder to think what users of these latest 1x11 systems do with their expensive chains and even more expensive cassettes.

reohn2
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Re: Chainwheel, Chain and Cassette Worn But Why Replace

Postby reohn2 » 8 Jan 2016, 10:32am

Further to my previous post...
I forgot to mention, could run the last(3rd) chain much longer longer perhaps to 1/8" elongation or more(say a further 2k+ miles) so long as the side slop isn't causing bad shifting,and IMHO it won't cause much more wear on the chainrings.
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