Your car, like mine, was designed to use 165/80 R14. My first P6 came with new 185/70 R14 tyres, which have almost the same rolling radius as the 165/80s, but they are unnecessarily wide and make the steering too heavy at low speeds. I replaced them with the correct 165/80s (Cinturatos, lovely tyres) and it was much nicer to drive: lighter, crisper steering, less road noise, a generally more agile feel. 175/80 R14 has too big a circumference and would cause the speedometer to under-read on a 2000. I have just fitted a new set of Vredestein Sprint Classics, 165/80 R14, to my current 1972 2000 TC and they feel just right.