i realized that Pakistan has less variety in tyre sizes..
so i am listing all tyre sizes that are good for cultus so you can choose what u like:
155/80/R13
165/75/R13
175/70/R13
175/65/R14
185/60/R14 (use on VXL or if you have fitted power steering)
155/65/R15
165/60/R15
175/55/R15
175/60/R16
all these tyre sizes will not affect suspension.. 15 inch and 16 inch tyres will make the ride very hard and these low profile tyres are not meant for heavy weight usage therefore if it is a family car then avoid it (kabhi kabhi chalta hai but not regular).. also these low profile tyres should not be used if u drive on rough or broken roads very often.. furthermore, 155/xx/Rxx has very low grip so i dont prefer those.. bottom line is that 14inch sizes are ideal if you really want to upsize..