You do not say which car you have and weight is a factor. The consensus seems to be about 24 pounds per 17" tire on a Cobra. Forget about 30 or more, you will wear out the center of the tire. There is no way one of these cars will load that tire to make it sit flat on the contact patch. I have a 6400 pound Suburban with low aspect ratio tires that are only 265 wide and it calls for 30 pounds on the pressure sticker.
If you have a FFR car, their are lots of them in the Bay Area, go to breakfast and ask. I had a SPF car with 15 inch tires and I had 18 pounds in each with 60 ratio TA's. I used 22 at the track. As these cars are virtually perfect 50/50 weight, you want the same pressure in all four tires. Unless you like the "Drifting" style of driving. All of the tires do the same amount of work whilst cornering with equal weight distribution.
You need slightly more in a 17 due to the decreased sidewall height. The best way to check is with a pyrometer after driving the car and not through the opinions of others, myself included. You want more or less even temps across the tire. You can get a pyrometer from here:
http://www.raytek-northamerica.com/c...ekNorthAmerica
They have them at NAPA as well. They are $80- , not a lot compared to the Cobra cost or a set of tires. It is the only way to be absolutely sure you have it right.
If you post the make of car, however, there will be lots of people who have a feel for it and will help you.
Now there will be all sorts of experts to follow to say that you need over 30 in each tire, stay tuned
Here is a photo of my car at Thunderhill with 21 pounds of air in the tires. I am turning through the esses at about 85 mph. Notice that there is basically no tire deflection at all. These cars are not heavy enough to push the tires out from the perpendicular. There is some rear squat as the car had a 427 FE and my foot is at wot.
Mulv - the guy who owned 3 Firestone stores just to get lower priced tires for the Firehawk Series. I'm not cheap, I'm thrifty....
