carful though, my old 15s measured 16" but where definatly 15".. same with the width, it measured less than it was. i think there are certain points you need to measure from etc. it should have the mesurements stamped on the wheels somewhere anywya.. or take em to a shop and get em checked properly.
if they are 14s.. get 175/50 .. they are a nice profile too. dont get 165/65... they will looks horrible and very chunky.
if there 13" x 5.5... get 175/50 R13s heh.. they are the best tyres ever