I have received a 4iiii crank power meter 170mm length that I can't install on my Merida trainer bike because it has square taper bottom bracket.

What would be the cheapest way to have it installed? Are there any adaptors that could be used? New crank set? Or perhaps just sell it and buy Assioma pedals?

  • 1
    You got the wrong part. You can replace the crankset to match, or buy the right part. It's up to you. Commented Feb 7, 2019 at 0:20
  • Just get a 5800 crankset (of same length) and BB, any LBS will install it and parts are cheap. Commented Feb 7, 2019 at 9:15
  • The linked bike has a mtb/hybrid triple crankset. Replacing it with road double is going to have some complications.
    – ojs
    Commented Feb 7, 2019 at 10:41
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    @Klaster_1 ojs makes a good point. Also might be better to have the LBS source the parts than risk bringing them the wrong one and expect them to fit it. If they order the wrong one it’s on them, for a start
    – Swifty
    Commented Feb 7, 2019 at 10:49

1 Answer 1


There’s no kind of adapter to fit the power meter crank to a square taper spindle, it seems to be a Hollowtech II left crank power meter (Shimano 105?). You’d need a crankset with the same Hollowtech II interface. You’ll need to check the width of the Bottom Bracket (B.B.) shell on the bike frame to see if a road crankset will fit.

Also note the gearing may change, with a road crankset, I think the spec says it’s a nine speed triple which you would want to match the best you can, probably Shimano Sora IF you have a road B.B. shell (68mm).

If you want to replace the crankset you’ll need to swap the bottom bracket too, which is no great obstacle, but might require tools you don’t have. Will also depend on the B.B. shell width.

Economics are up to you, you can add up the cost of the new crankset and bottom bracket plus tools or labour, and compare that to the cost of selling it and buying pedals.

I can foresee a case for the pedals, certainly it could be mechanically simpler to install pedals. You’ll have to see if it’s cheaper where in the world you live

  • Probably the easiest replacement crankset would be a Sora FC-3503 or the newer FC-R3030. A Tiagra FC-4603 would work, but I don't think they're available in black. The FSA 7420 square taper bottom bracket spec'd for the bike appears to be 68mm BSA-only, so any standard English-threaded Hollowtech II bottom bracket should work. Commented Feb 7, 2019 at 15:11
  • Hi @AndrewHenle - I am going to follow your advice and try to get Sora FC Crankset. I am having a good feeling this will do!
    – Peter
    Commented Feb 11, 2019 at 9:45

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