Im replacing the chain on my NC30 to a 520 and have a couple of unused renthals in the garage id like to make use of. I got a 39T and a 43T. Now standard gearing is 15/40 so i think most prople are gunna suggest 15/43 but ive dropped 1 tooth (which roughly equates to +3 rear) on a standard geared NC35 in the past and found that to buzzy when doing distance ridding.
Im thinking get a 14T front and use the 39T rear which if my maths are right that works out at having +2 at the rear, i reckon that'll be bob on for road riding but ive heard about certain bad combinations of sprockets, is the 14/39 one of them???

That will do nicely mate - prob need 102 links for it?

Prob not a bad call

Cool, just 14T front sprocket to get then