Want to go 1×9 or 10? Want the theoretical benefits of simplicity, ditching the weight of a shifter, mech and at least one chainring, and removing bar-clutter? Can’t afford a whole new drivetrain? OK – you’ll need some way to keep your chain nicely married to your front ring and the M:Part is designed to do just this, via an external bottom bracket-mounted plate which takes the place of a spacer.
Fitting was straightforward, literally a five minute job. The device is a top guide only, designed for use with rings from 32t all the way up to 42t and on a 9 or 10-speed drivetrain – no problems with my 33t. In use though, there were a few minor niggles. Firstly, the guide itself isn’t quite wide enough to cope with the range of my 10-speed set up. The upper two gears suffered slight chain rub. I eventually filed away a little material, which solved the problem. The back plate is also surprisingly flexible, which probably exacerbated the rubbing issues. Finally, the guide is a bit on the weighty side. Not a deal breaker for me, but it erodes some of the theoretical benefits I started off talking about and maybe contradicts that ‘XC’ moniker.
In conjunction with a clutch rear mech, I only lost my chain once while using the guide – after a prolonged rocky descent, and it bounced off the bottom of the ring so no fault of the guide. One pedal stroke and I was back in the swing of things. For much rougher riding, I’d consider adding a thick/thin-style chain ring, or swapping to a guide with a lower retainer, but for ‘a bit of everything’ riding, I didn’t feel the need for more.
Overall: At £30, the M:Part costs less than its lighter/stiffer competitors, but does suffer performance wise. It’s still a good value proposition though, and essentially does what it is designed to.