In my Punto Active, I have changed all four tyres to 15" Linea steel rims with 195/60R15 Goodyear GT3 tyres. The 5th tyre is still a 14" 165/80R14. I intend to buy a 15" steel rim for the spare tyre as well. The circumference of these tyres are as follows: - 165/80R14----------1948mm - 195/60R15----------1935mm (13mm less than the spare tyre) - 185/70R14----------1929mm (6mm less than 195mm tyres) - If I have to keep a difference of a few mm anyways, then I would prefer to keep 165/80R14 rather than spending on 185/70R14. - It is to be noted that you can drive with these tyres in case you replace a 15" wheel with a 14" wheel at the time of emergency but the speed is to be kept below 80kmph as mentioned in the manual. - Getting a 15" spare tyre in the form of Linea steel rim seems to be the best idea to me.