I have been told on numerous occasions that 245/40/17 will rub in the back and that the rear fender wells we need to be rolled.
I am also going 245/40/17 in the back with the rims in my sig. My mechanic has warned me that there will be rubbing. I have found a local shop that will be doing the rolling. There is always a chance of your paint cracking if the rolling is not done properly.
As for air pressure, the tire will usually have the suggested pressure marked on the side but this may not be the correct pressure for your car. Check your manual or the sticker on the b-pillar of your vehicle (sometimes the sticker is on the door underneath the locking mechanism made cisible when the door is open.
I got the text below from the link below. Hope this helps. http://www.type2.com/library/tires/tirefaq.htm
2. Tire Care: Inflation & Rotation
What inflation pressure should I use in my tires?
As stated in 1.G. above, recommended tire pressures are set by the car manufacturer, not by the tire manufacturer. They're stated in the owners manual as well as on a sticker in the door jamb or on the glovebox lid. It's important to check pressures frequently; at least once a month - more often if you find that you're losing pressure. For consistency, always measure pressures before driving when the tires are cold (parked for at least four hours; preferably overnight).
Tire pressure affects your car as follows:
Lower Pressures Higher Pressures
Ride more comfortable stiffer
Handling less precise better feel & turn-in
Wear more on edges more in the center
Gas mileage lower higher (less rolling resistance)
Tracking steady tends to follow grooves
Many car manufacturers are conservative (low) with their recommended pressures to maintain a comfortable ride. Drivers who push their cars fairly hard usually prefer a slightly higher setting. If you want to experiment, 32 all around is a good starting point - begin there adjust to your own preferences.
The outside temperature affects your tire pressures; a general rule of thumb is that a 10 degree fahrenheit change will change tire pressure by 1 psi. When temperatures are fluctuating, check your pressures more often. And if you check them in a heated garage, adjust for the colder outside temps.