Originally Posted by
tomato coupe
All else equal, I think the aero difference between 28 tires on 21 internal and 28 tires on 23 internal is in the noise.
I didn't notice any difference in ride quality or tire-fit appearance. I did notice going from a 37>50mm wheel made riding in the winds less comfortable. On the 37s the wind could be blowing however hard and I didn't notice any tug on the handlebars. The 50s aren't wildly uncontrollable, but I wouldn't take my hands off when it gusts.
28mm tire on a 23mm internal, with 30mm external becomes flush. The 28mm inflates to 30mm.