I suggest a 4-wheel alignment on a Hunter machine. Then a good wheel balance, also with a Hunter machine. (No, I don't work for them but am a big fan) My cars drive like a dream after doing both.
Anyway, here's how the Nittos will look on 15s. I got them from discount tires direct. They stick like glue, smooth as silk, but throw a lot of road debris and rocks under your fenders. If you get them, line the underside of your fenders with something like a dense foam hood liner material, or else you'll get spider cracks on your paint.
