The fact you mention 28 and 38's, I;'m figuring you have 700 wheels on a hybrid.
MTB wheel will not fit. They ar 26 in can usually labeled (26.2.1) or(26x1.5). Just examples.
On more curent roadie frames, it hard enough to fit a 700x 25. I have 700x 28 on our tandem.
If your'e talking about 700x38's on a roadie, forget about it!
