Hmm.. The recommended PSI for stock 18s are at 35 IIRC and I always ran mine at 40 for better fuel economy and better tire wear and I had no issues.My tire "guy" at Discount tire ran some numbers for me for my purchase. Going by weight (load) distribution at the corners, etc. etc.
He said my stock 17" on my EX should be at 33 PSI. After crunching the numbers for my 245/40-19s, he said the minimum PSI should be 33 and the MAX should be 36.
I don't know what these numbers mean exactly, but he said with the stock at 33 PSI, the load at the corners is at 1330. With the new tires at 36 that would be 1363.