If, on your cross-country/all-mountain rides, you seldom use the granny or big chainrings, then this could be an ideal option.
The idea is that you remove your front mech and inner and outer rings, and use the 1.X (as in 1x9) to keep the chain on the remaining middle ring.
It mounts to the bottom bracket shell behind the driveside bottom bracket cup and the chain runs through the hard plastic guide; you just dial in the chainline and that’s it.
Shifting performance at the rear is unhindered and, although we initially thought the guide might be noisy, in use – even through the rough – this proved to be untrue with the transmission running as quietly as with a standard front mech.
We only lost the chain when backpedalling on rough terrain, but still managed to pedal it back on and get moving again.
Your legs will have to work harder on the climbs and you’ll have to develop your spinning skills – generally a good thing for cross-country fitness – but it’s a huge weight-saver, seeing as you lose two chainrings, bolts, front mech, cable, shifter and some chain links.
It’s down to you to see if MRP’s 1x9 will work for the cross-country or trail riding you do, but if you’ve ever been tempted to try singlespeed but are afraid your area’s too hilly or you don’t have power to make it work, then this nine-speed option is worth investigating.
It's available in black or white, comes in two size options – 32-36t or 32-40t – and weighs a pretty dainty 58g or 62g respectively (due to the lack of a bashguard or bottom retainer). We met up with ex-world champ Brian Lopes recently and he uses one of these on his Ibis Mojo SL to great effect.