What is the effect of changing rim width on tire diameter? Specifically, if I mount the same tire on a narrower rim and on a wider rim, will the tire diameter be wider on the wider rim or narrower on the wider rim? Something tells me there is an inverse relationship between rim width and tire diameter. I am thinking that if the bead of the tire is squeezed more tightly together in a narrower rim, it will make up for that by bulging more at its widest point in diameter than it would if it were mounted in a wider rim. Am I onto something? And can you tell I am worried that when my new, wider rims arrive, I will no longer be able to fit my beloved 38mm tire between the chainstays?