Interesting topic! I found the below article that recommends the following for P-metric tires:

1. Never inflate a tire beyond the maximum pressure listed on the sidewall.

2. Start with 10% less than the maximum pressure, and work down towards the car manufacturer's recommendation until the right combination of ride comfort and handling is found.

3. Never go below the car manufacturer's recommendation.

http://www.agcoauto.com/content/news/p2_articleid/61

 

I usually run mines at 35 to 38 psi, any higher on oem size tires may result in wearing of the center tread. At 50 psi you are pushing the pressure limit of most tires, remember tires heat up while driving and pressure increase.

 

I think this guy is joking about the whole 50 psi thing guys, its a joke , i dont believe for one second he is running car tires at 50 psi, it probaly would have exploded soon as he hit a pothole, hope its not on a freeway at 65 mph, or he could loose alot more than just his car or tires. . 33 to 35 psi is just fine . 40 is already too high.

 

He's not joking at all. He's running ultra low profile tires on 22" rims, you have to run high pressures on tires like that. Its not the same as an OEM setup.

 

I just wanted to add the part about fuel mileage. People do all kinds of things and buy many different things to improve gas mileage. The best thing a person can do for their car is properly inflating their tires. 33psi is the low end of the good mileage side. Only a slight bulge on the tires. I have been told 35 is the ideal or maybe a bit higher for heavy cars. I just left the lexus dealership from some service and the paperwork said to set fire pressure to 35 psi. Having the tpms telling us the psi is great. Don't forget about checking in on your other cars. I personally kept my tires at 33 psi, but I think I will stay at 35 now. I usually notice the temps on my tires go up 2-4 psi when on the road. This can vary quite a bit depending on where everyone is at

 

Agreed.
Tires that are reinforced generally but not always need to run higher pressures then what the manufacture suggests otherwise you will ruin the inside of the tire.

The recommended tire pressure by the manufacture is based on a few things and that is the load placed on factory tires. Every car and tire needs to be matched and it is the air that supports the car not the rubber.
If you change to a different brand of tire but within the same size you may get away with the factory tire pressures but the optimal pressure is yet to be realized and that takes moving up and down a few PSI until it matches the tire.

 

Great topic, great thread!
I wouldn't have guessed the topic would be this widely discussed.
The tech at the tire shop went ahead and placed the pressures at 33psi and it rides a bit smoother.
Looking forward to having my control arms taken care of and wonder if the slight vibration I feel at higher speeds (60-70mph) will disappear with new arms (bushings).