Fingers is really the guy to ask - hes been a tyre fitter. Pressure does depend on the car almost as much as the tyre size. Weight and load have to be taken into account.
__________________ I got complimented on my driving today. There was a little note on the windscreen; it said 'Parking Fine.'
i agree with waynne. 25 sounds low, try it though see what it feels like, if the steering becomes heavy and sluggish then pump them back up again before driving too far otherwise youll end up damaging the tyres and wheels
Depends upon car mass and weight distribution. Strangely, the profile of the tyre seems to have minimal effect. All the air does is support the weight of the car bearing down on each roadwheel.
I always go up ten to fifteen percent over manufacturers figures. This gives the tyre a slightly stiffer behaviour which reduces tyre heating and therefore increases tyre life a little. It can also make the ride slightly harsher but I do like the faster steering response.
tyre psi 
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