Whats the narrowest tyre I can put on a 30mm rim?

I want to put some slicks on my 29er for pounding the roads on winter nights.

The outside width of the rim is 30mm (so probably 26mm inside). What would be the narrowest tyre I could get away with?

ta!

although I've never tried it, I would have guessed at a 27mm if we're talking 700c tyres ? could be tough to get on and off

thanks edhornby

I was thinking of something like these, but not sure whether to go with 37mm or 42mm….
http://www.wiggle.co.uk/p/cycle/7/Continental_City_Ride_Hybrid_Wire_Bead_Tyre/5360008050/

Can the daytime forum dwellers offer any advice!?

37 will be fine, 27 would give you very vertical sidewalls