I don't need more than one front chainring for my CX bike. Or, for my roadbike for that matter.

But if I try to just go minimalist up there -- and skip the front derailler -- once a ride I'll throw my chain.

The crazy thing is that I never notice the derailler making any "chain catching" sounds, like when it's saving a chain that would've otherwise fallen off.

And I can't find a pattern to the derailing.

So does it really have to happen? And do you really need some kind of guard to prevent it?

Let's see, singlespeeds don't have them.

And the front der only prevents derailing at the top. So something must be happening as a tight chain goes onto the ring after pulling past the top of the rear cog. But what? Is it a slight change in tension that allows slack which in time with some kind of sideways motion or bump throws the chain off?

I've tried one of those "shark tooth" things and I suppose that stops inboard derails. The chain would still sometimes fall off to the outside and cause bad trouble (like in a sprint).

Lately I just slapped a front der back on during summer use with a 53t front ring and racing rear cogset on a roadbike.

I'm now in CX season and I use the same bike for CX. So I now have a 40t ring up front and would like just to be shed of the excess front der. Maybe that shark-tooth would do the trick. Who knows, maybe small rings drop their chain some other way and might tend to more reliably keep a chain. I dunno. I guess I do hear about 'crossers using chainguards for single rings.

I just like to save all possible weight and would love to ditch that hunk o' metal there that's only keeping my chain on and doing nothing else.