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Hi, I want to convert my sons Cannondale f700 from a 3x9 to a 1x10, but keep the Shimano Deore XT Cranks. 1) Is it as simple as removing the outer and inner chainring, and installing a new narrow/ wide chainring in the middle slot? If so what chainring is best, 32T or 34T? The bike is an XCO race...