Standard fitments are:
1500 and 1800 - a 590-13 crossply (could be replaced by a 165R13 radial tyre) was fitted until 1965 when a 600-14 crossply tyre fitted on a 14-inch wheel (a radial 165R14 could be fitted, and was an option later in production).
1600 - 165HR13 or 185/70HR13.
1800ti - had a 600-14 crossply tyre, for which a radial 165HR14 would be a good replacement.
The Neue Klasse was a significant model for BMW, a small saloon choc full of advanced, quality engineering in a sober and stylish Michelotti body. Updated regularly it's the template for BMW's image today.