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I need to replace one chainring in my 3x9 setup. One possible option I'm looking at says it was made for 2x setups. Another option says it was made for 1x. They have the correct tooth count, BCD, and bolt layout. How much does this matter if the manufacturer says it was made for 2x or 1x setup? Am I going to run into problems using a chainring that was "made for" a 2x system on my 3x9 system?

(this is a follow-up to an earlier question: Does "speed" of a replacement chainring matter?)

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    Which chainring?
    – mattnz
    Commented Mar 30, 2021 at 20:38
  • I assume you've checked the bolts line up, but can you confirm explicitly?
    – Chris H
    Commented Mar 30, 2021 at 20:44
  • @ChrisH: Yes, BCD match, bolt layout matches, tooth-count matches.
    – FrustratedWithFormsDesigner
    Commented Mar 30, 2021 at 20:54
  • @ChrisH: That was my question about would a chainring made for a 10 or 11 speed drivetrain be OK with a 9 speed drivetrain. The question in this post is: I am using three chainrings so how much does it matter if the manufacture of a chainring says it's made for drivetrains that use one or two chainrings?
    – FrustratedWithFormsDesigner
    Commented Mar 30, 2021 at 20:58
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    I spotted that, and withdrew my close vote immediately, but apparently the auto-generated comment remained. Sorry for the confusion
    – Chris H
    Commented Mar 31, 2021 at 5:34

3 Answers 3

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Chainrings designed for multispeed systems have special pins and ramps in them, to assist shifting. Key word being assist. If you have rings for a certain config, it might not have those features in the right spots.

If you don't have them, shifting won't be as good as it would be otherwise. That doesn't necessarily mean it'll be complete garbage either, people happily rode bikes with "plain" chainrings for decades, and continue to do so today. But it won't be as crisp, or you won't shift as well under power, but you'll almost surely shift well enough.

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    container typo.
    – Nobody
    Commented Mar 31, 2021 at 12:45
  • Sounds like a 2x chainring on a 3x setup will run "good enough", at least until I have a budget for a complete drivetrain overhaul.
    – FrustratedWithFormsDesigner
    Commented Mar 31, 2021 at 13:25
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Additionally, a 1x chainring is likely to be "narrow-wide" to help with chain retention.

If you look closely, every tooth is alternately wider and narrower, so you place the chain on such that outside plates are around a wide tooth.

If you had used a FD to change chainrings, there's a 50% chance the chain will land wrong, and your wide tooth gets wedged inbetween two inner plates. This would stop the chain leaving the tooth at the bottom of the rotation, (chainsuck) and potentially could pop the side plates off the chain (unlikely but not impossible)

So a narrow-wide chainring will work very poorly on a multi-chainring setup.

Photo from chat

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    Also 1x thats not narrow wide often have longer teeth to help reduce chain drop - i.e. stop shifting to another cog
    – mattnz
    Commented Mar 30, 2021 at 22:52
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    You might actually emphasize this point even more. Multi-speed chainrings are designed to help the chain move on/off them. Single-speed chainrings are actually designed to keep the chain on. This explains why most new mountainbikes are 1x only. So the shifting experience will be horrible at best or non-existant at worst. While you might be lucky in getting the chain on them, you will probably not like the experience of trying to shift away from then.
    – anderas
    Commented Mar 31, 2021 at 12:20
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    Ok, so trying to include a 1x chainring on a 3x setup should definitely be avoided. Thanks for the info!
    – FrustratedWithFormsDesigner
    Commented Mar 31, 2021 at 13:21
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    Just for the sake of completeness - I think 1x "narrow-wide" chainrings are often thicker than multi-speed chainrings (at least the one I have from Wolf Tooth, I had to get longer bolts). That's an additional reason a 1x chainring probably wouldn't work well in a multi-speed set-up.
    – Evan
    Commented Apr 1, 2021 at 20:48
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    @bird seems reasonable - its easier to thin down every other tooth to make it narrow, rather than build up the wide teeth. So if the whole thing is the wide-tooth width then it would increase material usage, but decrease manufacturing time.
    – Criggie ♦
    Commented Apr 1, 2021 at 22:21
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More additional information for 1x setup: Besides bolt layout matches and tooth-count, on 1x there is an additional parameter: offset.

The chain-ring offset from the crank helps the chain get a good line towards the cassette on the rear hub. The chainline will differ on a bike frame with boost rear spacing and non-boost spacing, so there are different offsets on chain rings or spacers to get a correct chainline.

Chain line is explained a bit more here:
https://www.oneupcomponents.com/pages/understanding-chainline-for-optimal-1x-conversions-boost-and-non-boost

On a 3x setup, the chain rings will probably not have different options for offset.

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