I've been researching on the forum but couldnt find a definitive answer. If you want to go 1x10 with one of the new mechs with a "clutch" mechanism do you need a chain guide with a top AND bottom roller?
I'm guessing the clutch system will keep the chain tensioned so less risk of falling off the bottom.
Been a few threads on this... I'm just using a top one, worked fine on the Camber (tiny guide too) but not really tested it on the hardtail yet.
Lots of variables though.
Unless your hucking big drops or downhill racing a top guide will suffice for all round trail riding, i use a Pauls chain keeper bought from aspirevelotech in the states along with my short cage zee clutch rear mech running 11-36 cassette x 34 front chainring.
As far as I see it, it's a choice of either top & bottom guide or top guide & clutch mech. Both should ensure you don't lose your chain. Just a top or just a clutch mech and you'd risk losing your chain.
It does depend on the terrain and way that you ride though.
I have just fitted a Sram Type 2 shortcage rear mech on a hardtail. Previously had needed a top and bottom chain guide on a 1X9 or 1X10 set up. Tried it with just a top guide as an experiment (fully expecting to put the full top and bottom guide back on) but it works fine. Silent and chain not dropped once even on fast clattery stuff.
Really good upgrade and well worth it IMHO