See the following chart >>> https://www.wtb.com/pages/tire-rim-fit-chart

You should match the tire width to the rim width. So, for a 43mm wide tire, you should use a rim with an inner width between 19mm and 25mm for optimal performance, although you can use a rim with as little as a 17mm inner width. Anything less, and the tire will get a severe lightbulb shape, and roll sideways when cornering.