The resulting inflated tire width and height will depend on the rim internal width. More than likely a modern 28mm tire will measure 28 on your narrow rims. I bought new wheels going from 14mm to 19.5mm inside width. Basically increasing the circumference the circle. Now I cannot run 25mm tires. They fit but are too close and rub. My suggestion is first take some Allen wrenches and measure how much clearance you have to the sides and top. If you think a 28mm tires will fit then buy one 28mm of the flavor you want and try it on the front and rear. I so wish I could run 28mm tires. 25mm tires would even help smooth the road. I’m looking at gravel bikes for an all around bike. I could have two sets of wheels with one all road and one dual sport tires.