This is the closest I can find. I think this suggests that the important thing is the way that the water (in this case) breaks up as it leaves the wheel as is suggested by people above, though the details of I am a little less clear on. I need to admit that I haven't read the whole thing!
Thanks for the reply. The water drop analogy is useful. Does the 25% longer for the large tire come from the lower centripetal force on the tire? It looks like it is necessary to make some assumptions about the behavior of the stuff on the tire
Simon
Thanks - I hadn't thought about the larger wheel picking up more mud - an interesting extra variable!
In the end I think you are right that trials would be the way to go. This could get messy.
Simon
Do different sized bicycle wheel spray differently?
I was asked this question recently and have got myself confused with an answer. To expand on the question a little, when riding through mud at the same speed, which would spray the mud further, a 26 inch wheel or a 29 inch wheel? My thought...