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Want to ditch my basic square taper FSA Vero (50/34) crankset on 9x2 speed Sora drivetrain (2018 Devinci Silverstone 2) in favor of 105 compact crankset. I will attempt to get one in 50/34 not to mess up gearing.

First of all because it's FSA square taper, secondly 105 is lighter and I can get it locally used in great condition.

Obviously I have to replace the crankset and BB Potentially reuse BB (RPM, Square taper JIS) and FSA crankset in my old Raleigh rebuild, but this is separate story...

Asking if it is possible, if Yes what I have to take in account when doing this. Thank you

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    if you could be more specific in what your question is pertaining to, we might be able to give a better answer. are you checking if your new crank is compatible with the front derailleur? if you get your exact part model number (stamped on your crank and deriallurs, eg FC-R3000), shimano has good compatibility charts up here: productinfo.shimano.com/#/com/2.3?cid=C-453&acid=C-455
    – ludant
    Apr 16, 2019 at 16:14

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A 2018 bike with have an R3000 Sora 9 speed groupset. The problem here is that you have a 9 speed chain that probably won't shift well on an 11 speed crank.

As 10 and 11 (and now 12) speed systems were created, the cassette sprockets needed to be more closely spaced, which required the outside width of chains to be decreased. The distance between crank chainrings was also decreased to accommodate the narrow chains. The 105 crank will have the wrong spacing for the wider 9 speed chain.

A safer option would be to upgrade to a external bearing Hollowtech bottom bracket and a 2-piece Sora crank, or an equivalent 9 speed crank and BB from another brand such as FSA.

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    I though roller diameter and distance between rollers are the same for all chains, thickness is different. I thought of just keep using 9 speed chain. What I'm not sure about difference between 10 speed and 9 speed roller width and potential implications.
    – xchg.ca
    Apr 16, 2019 at 18:35
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    The problem here is that you have a 9 speed chain that won't work well with an 11 speed crank. I think it would work well enough. I'd think the 9-speed chain would probably be a little more likely to drop inside the small chain ring, and the shift to the big ring might not be as smooth as it would be with an 11-speed chain. But given that it's currently an FSA crankset - and probably a lower-end one at that - a 105 crankset would likely shift at least as well as the original FSA even with the wrong-sized chain. With the proper equipment, I'd bet the 105 would shift a lot better than the FSA
    – Andrew Henle
    Apr 16, 2019 at 21:20
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    @xchg.ca The inner roller width is the same, the outer width (roller+inner plates+outer plates) is narrower. See this answer
    – Argenti Apparatus
    Apr 16, 2019 at 21:21
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    (cont) I'd run it with a chain catcher to prevent dropping the chain inside the small chainring.
    – Andrew Henle
    Apr 16, 2019 at 21:22
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    @AndrewHenle You can't assume that an 11 speed crank will work with a 9 speed chain very well. From older related questions I've seen on this site the consensus seems to be you can get away with a 1 speed difference but not 2. I've pointed the potential problem so the OP is aware, and they can choose what to do with that information.
    – Argenti Apparatus
    Apr 16, 2019 at 21:27

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