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Old 09-28-12, 08:48 AM   #1
TallRider
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are teeth too worn on this chainring?

I bought a 180mm Dura-Ace 9-speed crankset on eBay, and the 53t chainring seems somewhat shark-finned. I've seen badly-shark-finned chainrings before and this isn't one of them, but it might be bad enough to skip.
For people experienced with this kinda thing, should I just toss the chainring, or at least try it and see if a new chain skips on it at all?
The last picture is of my brother's Campy chainring which was absolutely shredded.

(I'm not annoyed with the seller; the chainring was pictured close-up in the auction, and at 6'5" it's tough for me to find long crankarms and I have extra chainrings sitting around if need be.)

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Old 09-28-12, 08:58 AM   #2
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I'd say that's had it, from the last picture. Toss it.

By the way, a worn chainring on a new chain won't tend to skip. More likely, it'll produce severe chain suck, in addition to rapid wear on the chain.
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Old 09-28-12, 09:23 AM   #3
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The Shimano/Sugino rings on your crank look like they still have some life in them -- no harm in at least trying them, even though you did buy it for the cranks.

Your brother must really love his granny ring!
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Old 09-28-12, 10:28 AM   #4
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I'd say that's had it, from the last picture. Toss it.
The last picture is a truly badly worn Campy ring shown for comparison purposes. It is not one of the chainrings the OP is concerned about.

To the OP: the Shimano rings in the first three photos appear to have a lot of life left in them.
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Old 09-28-12, 10:29 AM   #5
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I'd say that's had it, from the last picture. Toss it.

By the way, a worn chainring on a new chain won't tend to skip. More likely, it'll produce severe chain suck, in addition to rapid wear on the chain.
When I say the last picture, I mean the last one of your ring. To be honest, Sheldon Brown's test would be a better way to tell.
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Old 09-28-12, 10:39 AM   #6
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The best test is... just run it, and see if it skips.
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Old 09-28-12, 10:47 AM   #7
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By the way, a worn chainring on a new chain won't tend to skip. More likely, it'll produce severe chain suck, in addition to rapid wear on the chain.
This.
Last summer I replaced a worn chain on a triple. After that I could not pedal 30' on the middle ring w/o the chain being sucked into the FD cage. On the small ring, there was a constant racket as the chain *attempted* to hang on to the ring, but was getting forcibly pulled off of each tooth. I had to replace the small & middle rings.
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Old 09-28-12, 10:48 AM   #8
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The Shimano ring seems fine. The worn/damaged areas you show, aren't badly worn at all. What you're looking at is the sculpting that was original to the new ring to improve shifting.
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Old 09-28-12, 11:07 AM   #9
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The Shimano ring seems fine. The worn/damaged areas you show, aren't badly worn at all. What you're looking at is the sculpting that was original to the new ring to improve shifting.
We really need a sticky in this forum with the title of "Are my chainrings or cogs worn or are they supposed to be this way?" and show pictures of what perfectly fine chainrings look like and how the lower teeth with the odd looking sculpting is intended by design for index shifting smoothness.
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Old 09-28-12, 11:13 AM   #10
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Thanks everyone.
@Airburst, good to know that chain suck and wear is more of a problem than skipping.
Does Sheldon's page give a method for measuring whether a chainring is too worn for a new chain? It looked like it only talked about cassette/freewheel sprockets.

I suppose the last picture of my chainring (the one that shows the Shimano and Salsa logos) is the worst-looking view of the Shimano ring.

My brother (whose bike had that Campy chainring) is a total romantic who thinks things will work out if your intentions are good. He rode 10k miles without servicing his chain. Eventually he rode only in the granny because the other two rings were so badly worn. This is the same guy who does 50+ mph descents wearing a Banesto cap (no helmet) because it is "authentic." Note the helmet hanging from my handlebars.
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Old 09-28-12, 11:20 AM   #11
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Thanks everyone.

Does Sheldon's page give a method for measuring whether a chainring is too worn for a new chain? It looked like it only talked about cassette/freewheel sprockets.
I'd assume the basic principle is the same regardless of which end of the transmission the sprocket is.

Anyway, FB has far more knowledge of these things than me, I'll defer to his opinion.
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Old 09-28-12, 11:24 AM   #12
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I suppose the last picture of my chainring (the one that shows the Shimano and Salsa logos) is the worst-looking view of the Shimano ring.
Download a photo of a new Shimano outer chainring from some seller's site. You'll see that it looks nearly identical to yours. Yout chaintings do some some wear, but IMO it's well less than 10% of the usable life.

We routinely get the same questions from people who look too closely at their brand new bike's chainrings. (search "is my new chainring defective" (or similar). Mount the rings, oil your chain and see if you can put some reasonable wear onto these almost new rings.
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Old 09-28-12, 11:30 AM   #13
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We really need a sticky in this forum with the title of "Are my chainrings or cogs worn or are they supposed to be this way?" and show pictures of what perfectly fine chainrings look like and how the lower teeth with the odd looking sculpting is intended by design for index shifting smoothness.
Add it to the list along with how to loosen a quill stem, wheel slippage in horizontal dropouts, threading forks, etc.

If we put some time into a sticky called FANQ (frequently asked newbie questions) covering this stuff we could probably cut traffic in the mechanic section by half. Then they'd have to cut their ad rates accordingly, then the forum wouldn't be profitable, then it might disappear, taking the sticky with it.

On second thought, maybe we should leave bad enough alone.
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Old 09-28-12, 11:55 AM   #14
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I'd assume the basic principle is the same regardless of which end of the transmission the sprocket is...
Yes, they are the same in general but there are some differences in the details. Most of the teeth on rings are longer and engage further through the chain than the teeth on the cassette. Cassette teeth are as short as possible to optimize shifting and just barely go past the mid-plane of the chain. A little bit of wear and they'll skip with a new chain. Also, the rings are larger than the cogs so the load is distributed over more teeth. It takes more dramatic and obvious wear before the rings will skip.

Agree that only the last pictured ring looks shot. Others look fine.
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Old 10-01-12, 12:07 PM   #15
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Thanks for the responses, FB. I hadn't seen your response when I made my second post in the thread - I guess the browser tab had been open for awhile.

I do understand that teeth on moder chainrings/cassettes are often shaped asymmetrically to improve shifting, and should have noted that in my initial post.
What stands out to me, particularly in the first and third pictures that I posted, is the consistent asymmetry (shark-finning) of the teeth. The right/forward edge of each tooth (that pushes the chain roller) is more vertical, and the left/rear edge is more slanted. That is the part where I wondered if it was normal/okay, or a result of significant wear.
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Old 10-01-12, 01:02 PM   #16
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i got some covers for my teeth. they've worn down from too much hard food and grain.
i usually wear them when i'm asleep.
maybe try something similar?
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Old 10-01-12, 01:15 PM   #17
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What stands out to me, particularly in the first and third pictures that I posted, is the consistent asymmetry (shark-finning) of the teeth. The right/forward edge of each tooth (that pushes the chain roller) is more vertical, and the left/rear edge is more slanted. That is the part where I wondered if it was normal/okay, or a result of significant wear.
I think you're right that you're seeing wear, but IMO it doesn't matter until the teeth are getting close to being hooked; in any case, aluminium being softer than steel, I find it hard to imagine how this would significantly accelerate chain wear.

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This is the same guy who does 50+ mph descents wearing a Banesto cap (no helmet) because it is "authentic." Note the helmet hanging from my handlebars.
I reckon that makes your bro tres cool. Even more so if he lives to a ripe old age.

But he really needs to have a think about drivetrain efficiency.
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Old 10-01-12, 02:08 PM   #18
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If we put some time into a sticky called FANQ (frequently asked newbie questions) covering this stuff we could probably cut traffic in the mechanic section by half.
I doubt it - there's plenty of evidence that New Posters Please READ THIS is seldom consulted, although it has so much fluff in it I almost can't blame folks. It does not matter how much info or resources one provides - someone always thinks there is a shortcut or that their problem is unique.

As for the chainrings, I agree they're fine - no chance of slippage and little loss in efficiency, though I'd not worry about necessarily going that large again. Part of the reason for wear is someone grinding a gear they are not fast enough to use.
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Old 10-01-12, 02:14 PM   #19
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I doubt it - there's plenty of evidence that New Posters Please READ THIS is seldom consulted, although it has so much fluff in it I almost can't blame folks. It does not matter how much info or resources one provides - someone always thinks there is a shortcut or that their problem is unique.
I was writing tongue in cheek. The next sentences should have made that obvious. I'm well aware that nobody reads stickies, and newbies don't read the PLEASE READ THIS section.
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