I have a 1998 Trek 7500 hybrid with 700cm wheels that I use for commuting. I'd like to put skinnier tires on it, but I think someone told me that they had to be 35's or so. It came with 38's. Can I put any road tires on them? I'd like to put maybe 25's or 28's. And can I use the same tubes (Schrader) or do I need to get new tubes as well?