[QUOTE=qasim.raza.5872;5111825]I would suggest you not to go for bigger rims!
They'll not only damage the suspension but would also decrease the fuel economy and maybe engine pick will decrease due to added weight. You'll need to go for a suspension overhaul at 60-70,000 kms instead of 100,000 kms. If i were you, i would not change the rims.
As far as the tyres are concerned, you should stick to manufacturer's recommended size for ideal performance but you can also go for 165 or 185 as 175 is not available mostly in 14 inch.
All vehicles have the suspension designed to accommodate larger size rims within acceptable specifications.
For Vitz, 14" to 16" is the specified range. When plus size rims are selected all other aspects (offset, rim dia and width along with tyre width and aspect ratio ) are calculated for proper rolling of the tyre.