Smallest rear CX tire clearance you'd be OK with?

[Lewis Moon]

I just slapped a set of Challenge Gravel Grinders on the X-Fire. They fit but with only ~5mm between the knobs and the chainstays. Seems a bit iffy but I'll be racing basically dry grass crits. Too tight?
The X-night seems to have more clearance.

[eBAUMANN]

if there wont be any mud, id say 5mm is fine.

[Lewis Moon]

if there wont be any mud, id say 5mm is fine.

What is this "mud" you speak of? Unless the organizer gets out a hose (or El Nino hoses us) there will be no wetness.

[Lovetoclimb]

For a good while I was using a bike that just barely fit a 33mm challenge on a wide rim. Never really noticed when mud was building up in the narrows but I am guessing (certain) that is why I never was able to hang with those cat 1/2 lead groups!