I'd want to exchange my triple crankset with double. After playing with gear calculator and testing some double setups, I came to the conclusion I need 36/24 gearing. I have 10 speed drive, so I'm looking for SLX/Deore crankset. The nearest combinations are 36/22, 38/24 by SLX (FC-M677). Can I buy 36/22 crank and change the lower chainring to 24T? According to Shimano technical doc, these parts are not interchangeable, but is this a real concern?

I'm going to use it with 11-36 casette if that matters.

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    If you can find the parts with the same BCD then they should fit. The tooth difference is getting smaller not larger, so the front derailleur shouldn't care. Shifting ramps might not line up properly, but that will only affect shifting from small to big(ger) ring. The other option is to stay with with one of the available combinations - two tooth difference isn't going to be massively significant. Personally I'd go larger to 38/24 unless you're building this for going up steep hills, in which case 36/22 would be my choice. – Criggie Jun 26 '17 at 10:16
  • @Criggie, thanks for your answer. Indeed I need a gearing for steep hills, but moreover I don't want extra large gap between gears on front. 36/22 gives ~64% of difference when upshifting – it would require around 3 gear changes on casette to balance the change. I tried 36/26 and liked it much better, but it lacks lightest gear I need. (I have 10 speed so increasing casette to more than 36T doesn't seem good idea) – koomahnah Jun 26 '17 at 10:52
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    it would require around 3 gear changes on casette to balance the change I'm currently riding 36/22 and I can vouch for this. – David Zemens Jun 26 '17 at 14:54
  • The new M6000 Deore groupo has a 10 spd 11-42t cassette I'm sure. The M6000 rear derailleur also appears to work with the last generation 10 spd MTB shifters too, so if that cassette worked for you, you need only replace the rear mech. – Bikebum Jul 2 '17 at 16:58

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