Rene herse has been doing those tests since 2006 "back when go-fast tires were 23mm." They covered a lot of variety and their conclusion is the aerial drag is tiny and real world conditions are more important than the idealized condition of tests on a steel drum.
The tests in the reference were done with a 21mm inner rim width. I believe that is neither super wide nor narrow. Arguably a good test bed rim to isolate the difference in tire.
Though, wide rim equates to a wide tire I do not think is true (at least, unsupported). The deep dish rims are only aero if the width is close to that of the tire. Reducing the ratio of tire width to rim width is aero! If anything, a wider deep rim on a skinny tire is increasing are dynamics. The aero dynamics of a wheel is not just a function of the tire alone. A deeper dish of more equal width to the tire helps that teardrop shape you want for aerodynamics.
The reference does go into some more detail why wide rim is desirable to reduce drag. I won't paraphrase further here other than to conclude a wider rim would actually be favorable for the skinny tire.Regardless, a middle of the road rim width was used in that data sample.
The tests in the reference were done with a 21mm inner rim width. I believe that is neither super wide nor narrow. Arguably a good test bed rim to isolate the difference in tire.
Though, wide rim equates to a wide tire I do not think is true (at least, unsupported). The deep dish rims are only aero if the width is close to that of the tire. Reducing the ratio of tire width to rim width is aero! If anything, a wider deep rim on a skinny tire is increasing are dynamics. The aero dynamics of a wheel is not just a function of the tire alone. A deeper dish of more equal width to the tire helps that teardrop shape you want for aerodynamics.
My knowledge of tire/rim ratio comes from conversations primarily. References for that ratio being important are not hard to come by, eg: https://silca.cc/blogs/silca/part-5-tire-pressure-and-aerody...
The reference does go into some more detail why wide rim is desirable to reduce drag. I won't paraphrase further here other than to conclude a wider rim would actually be favorable for the skinny tire.Regardless, a middle of the road rim width was used in that data sample.