Me and My cousine are using
185/65 r15
This is the best size for swift as well as city.
Road grip remains as of 185/60 but comfort increases much
Also if you drive car on rough roads
Tire pressure should be
26 front
24 back
If on normall roads like lahore
28 front
26 back
Tire pressure should not be more than 28 in pakistan for long life of your car chimtas especially suzukis.