Author Topic: How do my teeth look?  (Read 4085 times)

Matt2matt2002

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How do my teeth look?
« on: July 11, 2021, 01:39:37 PM »
New chain fitted at almost 0.75 after 4500+ miles and 23 months under a Chainglider.

KMC X1  110 LINKS 3/31 Inch taken off and same replaced.

Counted the links and 99 agreed with previous notes.

How do my teeth look?
Ring and sprocket both new in October 2014, 19,400 miles ago. Under the Chainglider.

I haven't flipped them.
Never drink and drive. You may hit a bump  and spill your drink

Andre Jute

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Re: How do my teeth look?
« Reply #1 on: July 11, 2021, 02:32:56 PM »
For a moment there I thought, Matt will have to join me in the dunces' corner reserved for chain wreckers and other mashers. Then I saw your chain did 4500 miles as distinct from the 4506 kilometres I reached on a KMC X8 when I threw it off at 0.5 on the checker.

Your mileage is a good 62% better than I achieved on what I considered a good life for the chain, and still a little better than if I had run that chain to 0.75.

Your teeth look good to me. I wonder though if there isn't a case for flipping the cogs to ensure even wear.

19,400 miles on a set of cogs, hardly worn!

mickeg

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Re: How do my teeth look?
« Reply #2 on: July 11, 2021, 02:56:17 PM »
I flipped my sprocket when it had maybe twice as much wear as yours, or possibly three times as much.

Just looking at a sprocket, it is hard to judge amount of wear.  But, the holes in the sprocket lined up initially with the teeth, and that makes it easier to judge wear.  If you specifically look just at one tooth and the adjacent sprocket hole, it becomes quite clear that on one side of the tooth, there is less metal between that hole and the sprocket cutout than there is on the other side of the tooth.  That shows how much metal has worn away.

Unfortunately your camera autofocused on the spoke heads, not on the sprocket, making it a bit harder to see.

The photo I attached is of my sprocket before I flipped it.  I run an sprocket with an even number of teeth (16 teeth) so every other tooth wears a bit different on mine.  I assume yours is a 17T which is what Thorn typically fitted, thus each tooth on your sprocket should wear exactly the same way.

I have concluded that it does not hurt any to run chains a bit longer on a Rohloff than on a derailleur system bike, other than sprocket and chainring wear.  But I have an even number of teeth on both my chainring and sprocket, so the teeth wear to match the chain wear, as every other chain link gets longer while the other chain links stay the same length.

I have decided that when my derailleur chains reach 0.75 percent elongation, I will set them aside to put on my Rohloff.  I am only putting new chains on derailleur bikes.  At this time I have three chains with 0.75 percent elongation waiting to be fitted to my Rohloff.  I need to ride my Rohloff bike more often, I replaced two derailleur chains last year.

steve216c

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Re: How do my teeth look?
« Reply #3 on: July 11, 2021, 03:08:30 PM »
I am about to hit 11,000km on a flipped socket and chain. I can tell you now that my photos do not look as unworn as yours. The bike was purchased with an estimate of 10,000km on it and sprocket / chainring are looking haggard. But only the last 5k had a Chainglider and I am convinced that most of the serious wear happened before it was fitted and exposed to the elements.

Iíll post pics in the next couple of weeks when I do the service.
 Steve
If only my bike shed were bigger on the inside...

PH

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Re: How do my teeth look?
« Reply #4 on: July 11, 2021, 05:18:58 PM »
Look fine to me, certainly wouldn't have considered changing the chain, but we do this one regularly...
My chains are on, 3,600, 4,900 and 7,200 miles, I haven't measured them, but I'm not expecting to replace any of them for a long while yet.

Matt2matt2002

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Re: How do my teeth look?
« Reply #5 on: July 12, 2021, 02:24:12 PM »
Many thanks folks. All good information and given graciously.

Andre:
Yes, 4500+ miles.
I thought I'd flip the ring and cog at next chain change.
( If I'm still here! )

Mickeg:
Good words on identifying the wear by looking at the tooth and adjacent hole. I can see some slight wear.
My set up is 38*17.
Fitting your worn 0.75 chains onto the Rohloff?
I take mine off for replacement at that point.
What is your reasoning?

Steve216c:
Looking forward to seeing your pictures.

PH:
Thanks for your comments.
So, you don't measure your chains routinely?
Looking out for a 0.5 or 0.75 change/wear point?
At what point would you change the chain?

Once again many thanks for opinions and my further questions are asked with respect.

The attached pictures were taken at the same time as fitting the new chain.
The EBB turned fine and the 2 screws gripped fine.
I noted that it could slide across but I'm sure I maintained the original ' line'.
And the position / rotation of the EBB looks ok?
Never drink and drive. You may hit a bump  and spill your drink

mickeg

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Re: How do my teeth look?
« Reply #6 on: July 12, 2021, 03:20:25 PM »
...
Mickeg:
Good words on identifying the wear by looking at the tooth and adjacent hole. I can see some slight wear.
My set up is 38*17.
Fitting your worn 0.75 chains onto the Rohloff?
I take mine off for replacement at that point.
What is your reasoning?
...

This article is the basis for my thinking:
https://www.sheldonbrown.com/chain-life.html

I cut notches in one tooth on my sprocket and one tooth on the chainring so that I can always put the chain back on the same way.  The notched tooth always gets a link that has outer plates over that tooth.

The chain elongation occurs at every other link, the links with outer plates.  And if you have an even number of teeth on your sprocket and chainring, every other tooth will wear to match your chain elongation.  I could see that every other tooth on my sprocket wore differently according to that theory.

So, I have no real reason to not put worn chains on the bike if I will keep the amount of wear on those chains to a rough equivalence.  For example, if I put a chain on with 0.75 percent wear and then take it off at 1.0 percent and put another one at 0.75 percent elongation on.

Yes I could keep putting new chains on it, but I would rather get some more use out of my old ones.

This won't work for you because you use a sprocket with an odd number of teeth.

I have no clue why Thorn has used a 17T sprocket as their standard, but I suspect that they are trying to keep the amount of wear on each tooth the same as adjacent teeth.  If I was running a bike shop, I would be inclined to do that too.  I doubt if explaining to a potential customer how sprocket teeth wear is a useful sales tactic.  But I worked in a bike shop years ago, I built up my Nomad Mk II from parts, and am an engineer by training.  I cut notches into the teeth on my bike when it was new based on that article, as I could see the logic in it.

mickeg

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Re: How do my teeth look?
« Reply #7 on: July 12, 2021, 03:44:06 PM »
...
The attached pictures were taken at the same time as fitting the new chain.
The EBB turned fine and the 2 screws gripped fine.
I noted that it could slide across but I'm sure I maintained the original ' line'.
And the position / rotation of the EBB looks ok?

The middle photo shows that the screws that lock the eccentric in place will be pressing in on a thin part of the eccentric.  Your eccentric is different than mine, so perhaps it is stronger and you can do that.  But I recall reading when I first built up my Nomad Mk II that the screws that lock the eccentric in place should press against a thick part of the eccentric so that the eccentric is not bent or deformed, other than the tiny little depressions that the screws will press into it.

Note the first attached photo, I have the thick part of my eccentric on the bottom where the screws are.

Second photo, just in case one of those screws gets loose, with a rubber band wrapped around both screws, they are unable to rotate and can't fall out and get lost.


PH

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Re: How do my teeth look?
« Reply #8 on: July 12, 2021, 04:05:03 PM »
PH:
Thanks for your comments.
So, you don't measure your chains routinely?
Looking out for a 0.5 or 0.75 change/wear point?
At what point would you change the chain?
No, never measure, not with a single chain line anyway, I don't see the advantage.  Worn chains works fine with equally worn sprockets and chainrings, the reason they don't work with a cassette is that the sprockets don't wear at an equal rate, so it'll start skipping on those less worn. plus the constant sideways flexing weakens the plates. 
I've never taken a chain to the limit, when the sprocket looks like it hasn't got much life left it gets flipped along with the chainring and a new chain added. That's usually around  15,000 miles and I'm quite conservative, I might see if the current ones last till 20,000. 
Neither do I waste much time cleaning chains, they get a wipe, oiled and the excess wiped of.
Each to their own of course and whatever makes you happy, with enough time and effort you could probably make a sprocket and chainring last a lifetime, but for me life's too short for that sort of bother.

PH

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Re: How do my teeth look?
« Reply #9 on: July 12, 2021, 04:06:35 PM »
Not mine, but this photo often does the rounds in such discussions, this is what a worn sprocket can look like  ;)
http://www.swedentoafrica.com/wp-content/uploads/IMG_0219_960x640.jpg

julk

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Re: How do my teeth look?
« Reply #10 on: July 12, 2021, 04:38:28 PM »
That sprocket has another trip or two in it.
This is what a worn sprocket looks like...

PH

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Re: How do my teeth look?
« Reply #11 on: July 12, 2021, 05:28:26 PM »
That sprocket has another trip or two in it.
This is what a worn sprocket looks like...
You win  ;D
Was that yours?

mickeg

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Re: How do my teeth look?
« Reply #12 on: July 12, 2021, 05:38:17 PM »
Not mine, but this photo often does the rounds in such discussions, this is what a worn sprocket can look like  ;)
http://www.swedentoafrica.com/wp-content/uploads/IMG_0219_960x640.jpg

From the lack of wear on the sides of the teeth, that one has an excellent chainline.  The photo I posted earlier of some of my sprocket teeth, you can see a lot of wear on the side of some teeth, that is from my chainline error.

julk

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Re: How do my teeth look?
« Reply #13 on: July 12, 2021, 05:48:28 PM »
You win  ;D
Was that yours?
Not mine - borrowed from a young lady who rode to and across Africa.

steve216c

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Re: How do my teeth look?
« Reply #14 on: July 19, 2021, 12:26:42 PM »
I am about to hit 11,000km on a flipped socket and chain. I can tell you now that my photos do not look as unworn as yours. The bike was purchased with an estimate of 10,000km on it and sprocket / chainring are looking haggard. But only the last 5k had a Chainglider and I am convinced that most of the serious wear happened before it was fitted and exposed to the elements.

Iíll post pics in the next couple of weeks when I do the service.
 Steve

No pics from me on this yet. Inspired by the photos from PH and Mick, and the desire just to push to the point just to see when things get silly, I did my oil change yesterday having just passed the 11k mark on reversed sprocket and Wippelmann Connex 808 chain, but decided to leave the chain and sprockets in situ until such a point that riding is affected by the wear on mine. My Truvativ chain ring is also due for replacement. I thought about flipping it (I don't believe the previous owner did this) but when compared with the replacement already on hand, the old teeth are getting so thin that I'm concerned that I won't get much additional use from the good side before teeth start snapping off.

My sprocket currently looks somewhere between Matt's pic and the photo Mick posted. When I reach the end of my experiment, I'll replace with brand new Truvative 42 steel chain ring, a new Connex 808 (purchased as on hand spare when I mounted the current one 11,000 km ago) and a new splined carrier with new sprocket to replace the old style sprocket still in use.
If only my bike shed were bigger on the inside...