My 1988 Mustang, which came with 225/60/15 tires, suggests 31PSI all around. I now have 245/50/16 tires on it, which aren't listed on the sticker. It wasn't until today that I considered that the tire might need more pressure due to being a lower-profile tire. I put 40PSI in them as a start, since some suggest using 80% of the max pressure which on these tires is 52PSI. So far I've noticed better gas mileage (on the trip computer) and better handling. They were at 31PSI, which I now believe is way too low for these tires. Anyone have any thoughts on the subject?