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I have a wild idea to replace a crankset on my Merida Crossway 500 (2014) (which is now SR Suntour NCX-FX-10s 48A-36-26 CG) with Shimano 105 5750 cCompact 10sp (switch from 3-speed to 2-speed).

The question is: will my older derailleur be compatible with new crankset?

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    If you are willing to spend money on the crankset (and a matching bottom bracket I expect, starting at USD15 on eBay for new piece), you might also be willing to spend money on a new derailleur (new Claris FD starts at USD16 on eBay) and a new flatbar road shifter (new Claris shifter starting at USD22 on eBay). That would allow you to use the 105 crankset. – Superman.Lopez Jun 20 '19 at 14:44
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If you want to switch from a MTB triple to a road double crank you'll need to replace the front derailleur and shifter to get the correct derailleur movement.

Putting a road crank on an hybrid frame designed for MTB components is problematic:

You'd have to find a road groupset that also has compatible flat-bar shifters. 105 5700 does not, the latest lower end road Shimano groups do.

I think (from looking at old reviews of the bike) you have a Shimano Hollowtech II bottom bracket. You very likely have the wider MTB version that fits on 73 and 68mm wide shells. A road crank spindle is made for the narrower road BB version for 68mm shells only and is therefore 5mm shorter.

There is also the problem of clearance between the larger chainrings and the right hand side chainstay.

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  • Ok, so basically 3-piece crankset is the best thing I could get for this frame and there is no way I could make my hybrid bike a bit closer to road, than MTB one? My main desire was do get bigger chainrings, but as I can see 48-36-26 is the best one I could get for MTB. Am I right? – gmltA Jun 20 '19 at 18:20
  • A 3-piece crank means one with separate spindle and left and right cranks and a square taper or splined interface. I think you mean a 3-chainring triple crank. – Argenti Apparatus Jun 20 '19 at 18:25
  • Basically you want a 2 chainring crank and larger chainrings for higher gearing, correct? There are double MTB cranks available that will take larger rings, and MTB double front derailleurs and shifters. The limiting factor is probably chainring/chainstay clearance. – Argenti Apparatus Jun 20 '19 at 18:28
  • That's true. But as I can see on all available 2-chainring cranks (at least from Shimano) amount of teeth on those rings normally lower, than in one I have right now. And I don't really see spare chainrings of the same (at least) size, which are compatible with double cranksets and 10-speed cassete. Or am I missing something? – gmltA Jun 20 '19 at 18:40
  • I don't think you are missing anything There is no significant market for MTB gear sets with more than 48 tooth chain rings. – mattnz Jun 20 '19 at 21:06
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No, that would not be compatible.

The MTB 3x derailleur makes a different movement than is required for a road 2x crankset. Also your shifters are for 3x crankset. You could try to come up with a hacky-solution (modify the chain cage, try to set your limit screws to some extremes, maybe you have a shifter that is configurable between 2x and 3x, etc, etc). But in principle it's not compatible.

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