I'm cleaning up my old (1986) Trek 520 that I haven't ridden in about 15 years and I've forgotten most everything I ever knew about bikes. I need some new tires and I need some re-education about tire sizes. I've got 700C rims...so far so good. It's the width that I'm confused about. Can I put pretty much anything on the rim..23, 28, etc, or am I bound by that particular rim, which I can't tell the size on?. What would be the reasons to have a 23 as opposed to a 35, etc? As far as tires go, for general riding on pretty good paved roads, do any of you have a real preference for brands? I was thinking either Gatorskins or Vittoria rubinos. Thanks.