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Just installed the CS-HG70 cassette and while doing some tuning, noticed that my chainring is no longer true, especially around the crank so am thinking about replacing the chainring set but can not find a decent 8 speed set but see a lots of 9 speed chainring set, can I use that instead?

Thanks

Nash04
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2 Answers2

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Ideally, you should stay with gearing designed for the number of gears on your bike. If you must use a different design, stay as close as possible to the original, and make sure you go to a larger number of gears, like the 9 speed you suggest.

If you do use a 9 speed chainring set, be prepared for your shifting to suffer to some degree. (How much depends on the exact brands and specifications of your original, and the new set you pick. No, I don't have any way to tell you what to pick.)

It's also possible that you may occasionally drop your chain unpredictably. If it happens even once, then you need to find a good 8 speed set again.

This is the 9 speed compatibility chart from Shimano.

9 speed chart

This is the 6/7/8 speed compatibility chart from Shimano.

678 speed chart

As you can see, there are no cranks listed as duplicated on both charts. /There is also a note indicating sub par shifting if even some closely interchangeable parts are used.

zenbike
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Yes; as long as you get a 7/8/9 speed compatible chainring set.

If you mean a strictly 9 speed labeled chainring set; Maybe. The more I look it seems opinion is divided between whether 6/7/8 speed chainrings are interchangeable with 9 speeds or not. A 9 speed chain is slightly narrower than a 6/7/8 speed chain, and this is especially important for the cassette. The distance from tooth-tooth is the same, though.

I've also seen some chainrings advertised as 8/9 speed compatible such as BBB Roundabout chainrings (8/9 speed compatible printed on the ring) or this set on eBay (Mowa MTB Chainring Set).

There is a possiblity that they are mistaken about the compatibility as @zenbike suggests, but both of those sources have good return policies.

It is worth noting that Sheldon Brown describes this as a non-issue in either direction.

Ehryk
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  • The reason you find disagreement is that too many mechanics seem to think that if you can bolt it up, then it must work together. And that too many amateurs think that they are qualified to hold an opinion on matters like this because they googled it, or even worked in a bike shop one summer when they were in high school. – zenbike May 06 '12 at 10:34
  • Adding to that confusion, it would seem, would be that 7/8/9 speed compatible chainrings DO exist (as demonstrated), while some are only 7/8 and some are only 9. Depending on your own experience, you would form different conclusions - sometimes it bolted up and DID work. – Ehryk May 06 '12 at 10:52
  • Anyone can simply state something as fact, yes. Being right is another thing entirely. The document linked here is the compatibility chart which includes the FC-M442 you referenced, and which someone's inaccurate forum post led you to believe was 6/7/8/9 speed compatible. As you can read, it isn't listed compatible with anything other than 9 speed. Drivetrain Compatibility chart – zenbike May 06 '12 at 12:10
  • You are correct that anyone can hold an opinion, of course. The trick is making yours the right one to hold. Also, please save your political references for somewhere appropriate. In case you are confused, that isn't on this site. We talk about bicycles here. I've flagged that comment as offensive. – zenbike May 06 '12 at 12:47
  • Fair enough. Answer edited to remove the FC-M442 reference. Is it your position then, that all 6/7/8 speed rings are not compatible with 9 speed chains, and vice versa? Or just the incorrectly linked Shimano ones? – Ehryk May 06 '12 at 13:05
  • Show me a set of cranks or chain rings listed as compatible for 6/7/8/9 speed by the manufacturer, and I'll reconsider, but that is my current understanding. By the way, since the reason for a difference in the chain ring is to make it possible to run a narrower chain, an narrower cogs, to fit more gears in a set space, i don't believe that possible. And I already stated in my answer above that they may work anyway, if not as well as the correct part. What I take issue with here is your definitive yes, and your listing as if the parts are designed to work together. Which is patently false. – zenbike May 06 '12 at 13:39
  • As for Sheldon Brown, he was right about a lot of things. But as has been noted elsewhere on the site, he had some blind spots. And he recognized that many things work together to a point, but are not as good as the appropriate part would be. – zenbike May 06 '12 at 13:54
  • I'm unable to find manufacturer claims (other than Shimano) either supporting or denying the compatibility. However, they are listed as both 8 and 9 speed compatible on JensonUSA, Excel, Cambria, the eBay listing above, and others. I'm not saying any chainring works with any chain, but that either A) dual-compatible ones exist or B) they're all lying – Ehryk May 06 '12 at 14:05
  • By the way, the manufacturer needs to be a real bike company, not a hong kong knock off selling on ebay. – zenbike May 06 '12 at 14:06
  • If I were in the situation of needing them, I would buy one of these claimed 8/9 speed compatible rings, and make sure I got a good return policy. If you have any issues or they don't work to your satisfaction, send them back. – Ehryk May 06 '12 at 14:07
  • I would do something similar. Or upgrade my bike to 9 speed. Which is what I said in my answer. But there is no way to say definitively yes, they are 100% compatible with no reservations. And since the OP stated his reason for buying 9 speed would be to buy a better quality set of rings, buying something which will degrade your shifting performance is a bit silly. Of course, he could do it anyway, as long as he understands the implications. – zenbike May 06 '12 at 14:11
  • The OP also used the tag Shimano, which indicates to me which brand's design matters here. – zenbike May 06 '12 at 14:14
  • SRAM offers their cranksets as both 8&9 speed compatable: SRAM S660. Does SRAM make your qualifications? Or do I need to find individual chainring sets (many manufacturers don't list them directly on their site, even if they make them). – Ehryk May 06 '12 at 14:26
  • Sure. Not for this OP, given the Shimano tag. But if he had SRAM components, sure. – zenbike May 06 '12 at 14:52
  • Edit the answer to remove the MTBR forum question as a source of authority, and the eBay seller reference, and I'll remove the downvote. – zenbike May 06 '12 at 14:55
  • Removed the forum post, but if I were the OP the eBay reference would be what would seem to solve my underlying problem. A chainring set that bolts on Shimano cranks that is (allegedly) 8/9 speed compatible, which do exist (SRAM and BBB). – Ehryk May 06 '12 at 21:02
  • The 2 sets of Campag rings you referenced on Jensen and Excel are useless. They are for road cranks, and from an entirely different species of products. They are in no way compatible. The third ring you referenced from Cambrian is a 5 bolt 110mm Race Face ring. Again unusable with a Shimano crank. The SRAM chainrings from that crank might be usable, but again are from a different, if more closely related species of drivetrain. Any other SRAM component can be written off as not compatible, but chainrings might be close enough. – zenbike May 07 '12 at 02:19
  • The eBay listing has no value, because it is eBay and I can list anything I sell as compatible with anything at all there. It is a non-curated site. The fact that they are Hong Kong grey market rings makes that a non solution. Regardless, simply repeatedly searching google for 8/9 speed rings does not an expert make. – zenbike May 07 '12 at 02:19
  • So you doubt they are what they say they are, I get that. However, if I was in OP's shoes, those would be how I would solve my problem. If they didn't work, I'd either mark them as 'not as described' and get my money back from PayPal, or use spacers to make them fit my 8 speed chain - not what you would do or are advising. – Ehryk May 07 '12 at 04:53
  • Since the OP is looking for the best quality, and has the option of * speed rings, per his question, that seems a foolish choice. If it is the only option, then that is likely what I would do also. As I have said already. 3 times. I'm concluding that you are arguing because you like to argue, and not because you are in search of information. I will not argue with you about this further. – zenbike May 07 '12 at 05:47