what tires and tire sizes you have? what rims do you have and what are their sizes?
Check the MAX tire pressure you have for your tires..
usually, for autocrossing, I go with -10 psi from max on my Kumhos 225/40s/18s.. and -5psi from max on my Paradas 215/35/18s... a good rule of thumb is to check up the max pressure and the maximum weight load for that tire.. You dont want to put too much pressure into the tires cuz they do heat up and will blow out at higher speeds, too low of a pressure will kill your power, mileage, or worse, easily cause a spin out or damage to the rim.
do a little bit of math by taking Max. Load divided by psi... this should give you an idea of how much to put into the tires, and how much each square inch of surface can support, it's just a general rule, not an exact number to follow by.
The sedans I believe weigh about 3800 lbs (with driver +/- 50 lbs), and 63% of the weight of the car is up front. You should end up putting a few more psis (2 to 4) into the front because of the weight of the car.. but remember, depending on how hard you drive, the tires in the front will heat up and expand the tires.. do a couple of tests in 2 to 3 weeks.. it never hurts to run your tire pressure just below max pressure of the tire.. say -5 to -10 psi from max.
I wouldn't recommend putting that much pressure in your tires unless you really want to wear them out as soon as possible. I work in a tire shop and I can't tell you how many people I've seen coming in with the center section of their tires balder than Mr. Clean all becuase they are overinflating them. It also depends on the tire, but I would never run my tires anywhere above 40psi. I burn through tires quicker than most here and I've found that if you get cheaper tires they are more prone to bad wear due to over/underinflation. Just thought I'd let you know, if you don't have any problems then don't worry about it.
Hey, if that's been working for you then stick with it. Tire pressure for plus size tires isn't an exact science and if you don't get any odd wear then keep them at the high pressure. I'm just relaying what I've seen and experienced myself.