If you only ever ride in the middle ring or you’re willing to sacrifice the extreme ends of your gear range in exchange for a quieter, lighter bike that’s less likely to drop its chain, a single ring upfront is a top idea. With the current 10-speed mechs from drivetrain giants Shimano and SRAM now available with clutch mechanisms, you can benefit from increased chain retention, and the extra gear over older 9-speed versions will be very welcome. A 1×9 drivetrain is still a great option, but you’ll need a full chain device (which can increase drag) to get the same level of chain retention, and you won’t benefit from the 36-tooth sprocket on steep climbs.
To make the 1×10 conversion you’ll need a dedicated single speed chain ring — this doesn’t have shifting pins or ramps, and the teeth aren’t cutaway like on a normal middle ring designed for use with a front mech. You’ll also need a chain device of some sort, such as the simple guide shown here (M:Part XC Chain Device, £29.99, madison.co.uk) and, depending on the thickness of your chain ring and whether or not you run a bash ring, shorter chainring bolts.