Thinnest tyre on a cx rim

[TomBikes]

I have cx bike and what it to be a bit more grippy on the crit track and a bit more zippy.
It has semi slicks on but i want to put road tyres on. Whats thinnest i could use? The rims are Weinmann SEC 16 32h rim and currently there are Clement X'plore 35 on there.

[Crawf]

They're 21mm wide rims I suspect, technically 23mm tyres will go on fine, but I'd suggest 25mm as a good all rounder.

[Nobody]

http://www.weinmanntek.com/Products/TREKKING/SEC16.htm

21mm outer, 16mm inner. Many road bike rims are this thin. You can easily run 23s on these. I have a 23 tyre (Durano) on a 24.5 outer, 19mm inner Mavic A719.