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I would like to replace my chainring for a bigger one.

I looked up my bike specs and it comes with a FSA CK-316BT, KSS, 42T chainring. I couldn't find any information about this, so I don't know how to buy a bigger chainring.

Here is a picture of what I am trying to replace, I am trying to replace only the chainring and not the whole chainset.

chainset

My question is, what type of chainring can I use to replace my current one?

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  • Single-speed? Of so, just put a smaller cog on the rear wheel.
    – Andrew Henle
    Commented Aug 22, 2018 at 10:07
  • @AndrewHenle fair point - but mechanical efficiency drops off at around 12 tooth and is worse on 11 tooth. If its a fixie, then braking/skid patch ratios come into it too.
    – Criggie ♦
    Commented Aug 22, 2018 at 11:00
  • @AndrewHenle yeah single speed, I have a 16T cog, having a hard time finding a 14T and was not sure that would be a good idea.
    – simao
    Commented Aug 22, 2018 at 13:03

3 Answers 3

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The main limiting factor is chainstay clearance. If your chainrings touch the chainstay it will wear and weaken and eventually fail. So the first thing is google your bike frame and see what maximum size chainring its rated for. Do this first.

Once you have that info, get onto Sheldon's gear calculator https://www.sheldonbrown.com/gear-calc.html and play about with the numbers. Will changing from 42 tooth to your maximum tooth give enough difference to notice?

Finally, print this PDF https://cdn.shopify.com/s/files/1/0230/9291/files/BCD_finder_tool_v2.pdf in 1:1 scaling, then put your chainring directly on it and see which BCD matches.
Note that 102 and 104 are very close as are 94 and 96.

Armed with those numbers then you can go shopping. Make sure you fit a new chain (it needs more links anyway) and a new cassette.

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The only thing I can find for this crankset is the triple version of it. See: http://www.chainreactioncycles.com/de/de/fsa-ck-316ttt-alu-kurbelgarnitur/rp-prod151698

The Bolt circle is stated as 104mm but as you got a 4-bolt crankset you can easily measre the diameter by measuring how much apart are the centers of two diagonal bolts.

Then you can just buy a new chainring for this diameter and change it.

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I've searched for your crankset and found a replacement chainring:

enter image description here

Now, this specific chainring is 40T so no use to you. However, it tells us that it is 104mm BCD (bolt circle diameter) - check yours if it says the same. Once you have the BCD measurement you check that it is 4 bolt and basically it's all you need to know to find a chainring that fits your crankset.

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  • OP's chainring is a 42T now, and they're asking for a larger one for more high gears.
    – Criggie ♦
    Commented Aug 22, 2018 at 10:58
  • 3
    OP is asking "what type of chainring can I use" and my answer is "check your BCD, most likely it's 104 and I clearly see it's 4 bolt and these are the parameters that determine whether the new chainring fits your crankset". We are not a search engine for products' offers, are we?
    – Mike
    Commented Aug 22, 2018 at 11:24
  • @Mike your answer was very helpful yes, I just needed to know which type of chainring, I can just try to find a bigger one. thanks
    – simao
    Commented Aug 22, 2018 at 16:32
  • Mike, I edited your answer to try to avoid the misunderstanding that @Criggie made. Of course, if you don't like the edit, undo it but it would probably be helpful to make some change along those lines.
    – David Richerby
    Commented Aug 22, 2018 at 17:01
  • @mike I understand - sorry for being confused :)
    – Criggie ♦
    Commented Aug 22, 2018 at 19:41

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