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Question about chainring wear

Old 11-08-18, 08:34 PM
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techie
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Question about chainring wear

I'm swapping some parts onto my bike and upon closer look at the chainring, it looks like some of the teeth are worn down a bit compared to the others. Is this an issue? It looks like I can unbolt the crank arms and replace the chain rings on here if I need to since they aren't riveted.

also, I currently have a 2x7 drivetrain with a 48t large chainring. Can I keep the front chain rings while swapping the 7 for an 8 in the rear? The one pictured below is 52t

Last edited by techie; 11-08-18 at 08:48 PM.
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Old 11-08-18, 09:29 PM
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The large ring does show wear, but I doubt it will cause any issues for a while longer. Besides the different tooth profiles due to the shift sections the teeth the teeth at the point of power (with the RH arm at 3:00 the teeth at what would be the top of the ring, and with the LH arm forward the now different top teeth too) will wear faster then the teeth at the point of less pedal power. Back in the day we used to rotate our rings every so often to even out the wear. These days that would change the rotational locations of the shift gates, not a big deal for riders who know how to shift well.

As to the crank being compatible with an 8 speed cog set, Yes. Andy
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Old 11-08-18, 09:30 PM
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I am no means an expert but they do look pretty warn and "sharp" looking. I would probably replace those. Have you asked your LBS? I usually have my mech give me a the final word but they look warn to me. I am sure someone with more experience will chime in though.

Chain rings are defiantly a wear item.....I would bet most folks push them way to far
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Old 11-08-18, 10:23 PM
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I usually take a hard look at chainring wear whenever I replace the cassette/chains, and replace rings as necessary. Certainly for Campagnolo, loose chainrings are pretty expensive - it's usually more cost-effective for me to buy a whole NOS crankset, transfer the rings to my current crank arms, and eBay the new arms.
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Old 11-09-18, 06:16 AM
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They look worn to me too, but do they cause any problems? Swap them if you want. Or clean them too. Also, that set is 53/39 not 52.
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Old 11-09-18, 10:52 AM
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I think you large ring is fine. The teeth profile are different on "modern" chainrings, they are not uniform by design. The teeth just "after" the shift pins are lower to assist with the chain engaging with the large ring. I have seen this explained better elsewhere on the internet (believe there is even a video showing this). I only change the chainring if I start getting chain suck or, after installing a new chain, I get audible grinding/clicking or other unpleasant sounds indicating the new chain isn't meshing well on the old ring.
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Old 11-09-18, 11:00 AM
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Lay a brand new chain around it and see how much slop there is ... yet?
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Old 11-09-18, 11:02 AM
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Originally Posted by techie View Post
I'm swapping some parts onto my bike and upon closer look at the chainring, it looks like some of the teeth are worn down a bit compared to the others. Is this an issue? It looks like I can unbolt the crank arms and replace the chain rings on here if I need to since they aren't riveted
The shorter teeth you see were like that when these chainrings left the factory. That's a feature, not wear.
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Old 11-09-18, 11:21 AM
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I would clean them and use them, they look worn but not worn out. Also going from a 7 speed to 8 speed cassette will not effect your chain rings as the both use the same width chain.
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Old 11-09-18, 12:24 PM
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( By the way, it's easier to diagnose in photos if the chainring is clean. )

Here's a crop, rotated, from your photo:
The two teeth on the right are machined to that truncated shape at the factory. It's designed to help shifting onto the big ring.

The shiny wear on the face of the teeth is normal, and doesn't affect performance.

The back sides of chainring teeth often look "rounded off" or "worn down", but the chain doesn't press against those sides. It's just shaping to help when shifting. The ring turns clockwise, so the chain rollers press against the right side of the teeth.

The teeth at the pink lines might be a little worn. But like the other comments, it's probably still okay.

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Old 11-09-18, 12:36 PM
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Here's normal, minimal wear, an Ultegra 11-speed at 5000 miles.
The small ring has identical teeth, since the chain just lifts off this small ring. The big ring has factory shaped teeth.

This back side view rotates counter clockwise in this photo.


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Old 11-09-18, 04:35 PM
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Thanks for the info! Got them apart, cleaned and painted the cranks with automotive paint at work with a matte clear.

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Old 11-09-18, 05:50 PM
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That looks good!

For best shifting, you'll want to remount the small ring one bolt hole clockwise from where it is now. See that little tab with the stamped triangle at about 6:30 in your pic? It's supposed to be hidden under the crank arm.
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Old 11-10-18, 06:01 AM
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Originally Posted by ThermionicScott View Post
That looks good!

For best shifting, you'll want to remount the small ring one bolt hole clockwise from where it is now. See that little tab with the stamped triangle at about 6:30 in your pic? It's supposed to be hidden under the crank arm.
thanks for the info! I saw the piece to line it up on the large ring but couldn't tell if there was one on the small one.
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Old 11-13-18, 08:16 AM
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Are those the same chainrings? They don't look bad to me at all now that they're all cleaned up.
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Old 11-13-18, 09:34 AM
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Hence my thought that there's more miles left on that large ring. Andy
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Old 11-13-18, 11:23 AM
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Originally Posted by Retro Grouch View Post
Are those the same chainrings? They don't look bad to me at all now that they're all cleaned up.
I always shake my head when I see someone offering up really grungy cranksets and freewheels for sale. It's like "c'mon, you're leaving money on the table by not doing a couple minutes of work to clean this stuff!"
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