Have 2003 2.7T 17 inch wheel (225/55/17 tire spec). With little cargo and 1-2 people
in the cabin, 29 psi is recommended for normal speed by manual. As I was reducing the psi
from 35psi, now at ~ 33psi, the bulge at the tire bottom appears big. So I stopped and
kept the pressue at 33psi. Should I go down to 29?
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Having read replies, I double-checked the manufacturer guideline on the door trim sticker.
For 225/55/17, for normal speed, for 3 people and 1 cargo, it is 29 psi for both. If 5 people and 3 cargo, it is 39 and 42 psi. Puzzling huh?

 

I think you misread the tire pressure info. Check on the inside of the door. 29 psi is waaay too low. I can't get out to my car to confirm what the pressure should be, but I think it's 39 psi front and 42psi rear. At 29 psi, you'll probably get 10mpg and chew up the tires fairly quicly with any highway driving. The car would also drive like a slug with such low pressure in the tires.

 

Based on experience with Porsches and Audis, I tend to set my tire pressure at the high end of what is posted on the tire sidewall rather than the tire sticker on the car. The resulting mileage and tire wear is better however the ride quality can be impacted. I tend to run my Allroad's Yokohama AS430 summer tires around 40 lbs.