fcyu

So recently I started biking again, and i decided to buy an old Road Bike for the heck of commuting rather than relying on public transportation and driving everywhere. Ever Since I can remember, I never utilized the potential of changing gears on a bike, so I always stayed in one gear set, my cousin was talking to me about changing it up a notch or two to a fixed gear or a single speed bike, in honestly i would prefer a single speed. Well, anyways.. enough of that, The gear i run on the Road Bike is 39 on the front and 25 on the back. Is is possible to get a 25t for the rear tire if I was to build up a bike from a frame up?

PS. I tried out 39/17 and it wasnt quite bad, but i would prefer if 39/25 was possible.

Thanks, Jason