I do have the old Performance 505 MTB I started my commute on before the 520, but I had switched to 26x1.5 city tires on that. Less tread then the 700x32s. I saw that Clement has a new CX tire the X'Plor MSO with plenty of knobbies and a center rib. They come in a 700x40 which I think will fit on the 520. I like that thought because I can also use them on my unpaved rails-to-trails rides.