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Time for new chainring? Pic attached

Old 10-21-15, 07:26 AM
  #1  
illusiumd
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Time for new chainring? Pic attached

Wondering if the teeth on outer ring look ok here

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Old 10-21-15, 07:31 AM
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Look fine to my eyes. Why do you ask? problems? Andy.
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Old 10-21-15, 07:33 AM
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Can't see the teeth on the small ring, but the big ring is shot. Notice that the teeth are not symmetrical. The right side of each tooth is worn down.
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Old 10-21-15, 07:41 AM
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There is some slight wear, but I'm with Andy - is there a problem you are trying to address? As long as you are replacing the chain regularly the wear shown should not cause significant problems. On the other hand if you like things to look better and want a little smoother feel (given a newer chain also - and then you may need a new cassette) then go ahead and change it.
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Old 10-21-15, 07:47 AM
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Originally Posted by cny-bikeman View Post
As long as you are replacing the chain regularly the wear shown should not cause significant problems.
So, how often should I be replacing a chain (approximate miles)? I don't have one of those fancy chain gauges.

Should I be doing this before I sense issues resulting from the chain or when the problems happen?
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Old 10-21-15, 08:01 AM
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Originally Posted by curtiseddie View Post
So, how often should I be replacing a chain (approximate miles)? I don't have one of those fancy chain gauges.
Don't bother with those chain checkers, they are notoriously inaccurate. Instead, measure 12 links and replace the chain when they measure 12 1/16"; a new chain is exactly 12 inches. Mileage is irrelevant.
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Old 10-21-15, 08:12 AM
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Originally Posted by curtiseddie View Post
So, how often should I be replacing a chain (approximate miles)? I don't have one of those fancy chain gauges.

Should I be doing this before I sense issues resulting from the chain or when the problems happen?
Concerning the big ring, maybe I'm too picky, but I see at least two teeth that are missing their tops. They are on either side of the two topmost teeth. All the teeth slope visibly to the left.

Here's a possibility: The big ring may have been taken off and reversed. Normally, wear should occur on the front of each tooth, where it pulls against the chain. In your picture, that would be the left side, not the right. In that case, the chain ring is still okay, but the broken teeth may cause problems. (Your crank is apparently a double, and we are viewing it from the non-drive side.)

I blew the photo up to max size and viewed it with a magnifying glass. That showed me what I would see if I were looking at the ring in person. You should also check your rear cogs for symmetry and even height.

I have two bikes with extremely old steel chain rings that look far better than yours. One is on a cottered crank from the 1960s. But, as I said, I'm perhaps too picky. (Anyway, it's not the age af a part but the mileage that counts.)

Last edited by habilis; 10-21-15 at 08:35 AM.
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Old 10-21-15, 08:20 AM
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Modern chainring teeth are not all identical. They have different profiles to aid in shifting, depending on what part of the crank they are on.
They look fine.
The large chainring takes a loooong time to wear out.
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Old 10-21-15, 08:31 AM
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+1, the teeth got shorter to speed up shifting, many mistake that as wear they did.

I suspect this is another case .. Put a brand new chain on and see if it works OK.
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Old 10-21-15, 09:04 AM
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Originally Posted by Homebrew01 View Post
Modern chainring teeth are not all identical. They have different profiles to aid in shifting, depending on what part of the crank they are on.
They look fine.
The large chainring takes a loooong time to wear out.
I know I'm belaboring this, and I apologize. This is more for my own education than to start an argument.

The second tooth from the left is shorter than the others. Count three teeth to the right, and another tooth is shorter. Count three more to the right and that tooth is shorter, too. Seems like a regular pattern, but if you go three more to the right, that tooth is normal height. If the ring was designed this way, is it likely that uneven teeth would occur at irregular intervals, especially since rings can be removed from spiders and mounted in a new position relative to the cranks? (I must be watching "Forensic Files" too much.)
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Old 10-21-15, 09:10 AM
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The shorter teeth are not all the way 'round, and they are indeed shorter by design - simple as that. Such rings are meant to be mounted in a specific place in relationship to the spider. Again, unless you have having a specific problem or just want a fresher looking ring or slightly smoother feel the chainwheel is fine.
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Old 10-21-15, 10:08 AM
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Another chiming in to say there IS wear, but it isnt bad enough to trash the ring.

-SP
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Old 10-21-15, 10:40 AM
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Originally Posted by cny-bikeman View Post
The shorter teeth are not all the way 'round, and they are indeed shorter by design - simple as that. Such rings are meant to be mounted in a specific place in relationship to the spider. Again, unless you have having a specific problem or just want a fresher looking ring or slightly smoother feel the chainwheel is fine.
If we had a picture of the full crank, you'd be able to see the various locations of the shift pins and those short teeth would coincide with those locations. Definitely not wear.
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Old 10-21-15, 10:41 AM
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Originally Posted by habilis View Post
Can't see the teeth on the small ring, but the big ring is shot. Notice that the teeth are not symmetrical. The right side of each tooth is worn down.
Not worn out. Not shot.
This is how new chainrings come from the factory now. The teeth are asymmetrical, and are not all the same shape, either. It's to help shifting the chain.

Remember, this is the backside of the chainrings. The force against the teeth is on the left side, not the right.

OP--the chainring looks barely used. The flat sides of the teeth will quickly show wear, but it doesn't cause any problems. And big rings last a very long time.

Last edited by rm -rf; 10-21-15 at 11:10 AM.
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Old 10-21-15, 10:42 AM
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The shorter teeth are absolutely there by design, and you can compare to a brand new chainring to confirm. They're placed in locations relative to other shifting aids like ramps and pins, and they allow the chain to climb up onto (or off of) the chainring more easily.
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Old 10-21-15, 10:48 AM
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The chainwheel itself does not care about our consensus. But, people reading this might ....

There is some minor wear on that big ring, as in just broken-in. The irregularities are intended by the manufacturer. Modern chainrings come with a few weird features, bevels, shot teeth pins, grooves, etc.. Think about it, wear would be more or less even all the way around. Not every third tooth, part of the way around.
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Old 10-21-15, 10:56 AM
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Shimano first started to use height differentiated teeth to aid shifting way back in the early 1980s. They called it "W cut". I have done the same to symmetrically cut chain ring teeth to aid their shifting. It works. We get calls at work about someone's new bike having already broken the teeth tops. We say to look around at the other teeth and that one will see more, but that these teeth still have their anodizing on the "broken" face. Or in other words these teeth are made that way.

The OP has yet to respond to our questions as to why they are concerned. Inquiring minds are waiting. Andy.
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Old 10-21-15, 10:58 AM
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I'll chime in and say the same thing. The shorter teeth were made that way. If you buy a brand new chainring, never been used, it will have some shorter teeth and some teeth shaped differently than the others.
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Old 10-21-15, 11:09 AM
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Here's a new Campagnolo Athena chainring, with less than 200 miles on it. The complicated tooth shapes really show up here. The non-contact back sides of the teeth are sloped more than the fronts.

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Old 10-22-15, 07:24 AM
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Originally Posted by Andrew R Stewart View Post
Shimano first started to use height differentiated teeth to aid shifting way back in the early 1980s. They called it "W cut".
I think it was a Tri-color set I bought the first time I saw the "W cut" sticker on it and asked the shop what the heck was "W cut", we all speculated until someone saw the pattern and made a good guess.
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Old 10-22-15, 07:52 AM
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Originally Posted by habilis View Post
I know I'm belaboring this, and I apologize. This is more for my own education than to start an argument.

The second tooth from the left is shorter than the others. Count three teeth to the right, and another tooth is shorter. Count three more to the right and that tooth is shorter, too. Seems like a regular pattern, but if you go three more to the right, that tooth is normal height. If the ring was designed this way, is it likely that uneven teeth would occur at irregular intervals, especially since rings can be removed from spiders and mounted in a new position relative to the cranks? (I must be watching "Forensic Files" too much.)
Look at the short teeth again. The short ones are near the pins and ramps of the chainring. The longer teeth are between the pins and ramps. It is, indeed, a design feature which allow the chain to be picked up and released quicker. Definitely not wear.
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Old 10-22-15, 08:14 AM
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Originally Posted by rm -rf View Post
Here's a new Campagnolo Athena chainring, with less than 200 miles on it. The complicated tooth shapes really show up here. The non-contact back sides of the teeth are sloped more than the fronts.

I guess cost is no object for Campagnolo customers, but how does a company like Shimano do this cost effectively? It looks like it must involve, not one, but many hand operations with a grinder. Does anyone know how it's done in the factory?
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Old 10-22-15, 08:19 AM
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Originally Posted by habilis View Post
I guess cost is no object for Campagnolo customers, but how does a company like Shimano do this cost effectively? It looks like it must involve, not one, but many hand operations with a grinder. Does anyone know how it's done in the factory?
Some combination of CNC machine, forging dies, stamping dies, or die casting tooling depending on the components. I doubt any of it is done by hand.
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Old 10-22-15, 08:24 AM
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Originally Posted by habilis View Post
I guess cost is no object for Campagnolo customers, but how does a company like Shimano do this cost effectively? It looks like it must involve, not one, but many hand operations with a grinder. Does anyone know how it's done in the factory?
I don't know, but if I had to guess I'd say that they probably grind all of the teeth symmetrically (easy) then go back with a machine that only grinds specific teeth. (Bit more hard). Nothing an automated grinder couldn't handle when the chainring is on a mount that spins to the right place.
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Old 10-22-15, 08:44 AM
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Originally Posted by habilis View Post
I guess cost is no object for Campagnolo customers, but how does a company like Shimano do this cost effectively? It looks like it must involve, not one, but many hand operations with a grinder. Does anyone know how it's done in the factory?
Campagnolo and Shimano are pretty close in cost when comparing similar product lines.
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