spoon2000

I have mine set to 37 all around and it seems to work well.

For the most part, the "right" tire pressure is a compromise. Too few PSI in the tire, and the contact patch (meaning the amount of rubber that contacts the road) is too big, which means greater rolling resistance (and thus worse fuel economy), poor handling (because the sidewalls can flex more in corners), and greater heat (because excess flexing of the tread and sidewall creates excess friction, and the resulting extra heat can lead to tire failure as we found out with the Ford Explorer and Firestone tires), to say nothing of abnormal treadwear (without enough air, the tire rides mostly on the parts of the tread at the inner or outer edges).

Too many PSI, and rolling resistance drops, but at the expense of comfort, treadwear (overinflated tires wear fastest in the middle), traction and handling (if the contact patch isn't big enough for the tires to grip the road adequately during cornering or acceleration), and potentially safety (an overinflated tire that hits a sharp object like a curb or pothole isn't able to flex to absorb the hit and thus has no choice but to blow out at the point of impact).

To optimize contact patch size, car manufacturers can load a car with varying amounts of weight in the seats/trunk and varying amounts of air in the tires, put the car sitting on a sheet of transparent material, and then take measurements and come up with what they feel are the best solutions. This is why it's a mistake to inflate tires (as some do) based on the maximum pressure information written on the tires themselves.

snagitseven

37 PSI in the back is too firm a ride for me with the sports suspension on the crappy New England roads (unless I've got a full load in the trunk on a trip, then 39 seemed to work best). It's really a matter of taste and localized road conditions (and, of course, load) as to where to go between the normal and max recommendations in the manual.

dcmetro

Thanks for the reply guys. Think I have mine at 38 now..will bring it down

ultrahertz

So last week I was driving in NJ on an out of state road trip with the family and hit some massive pothole or something on an entrance ramp to I287.

I inspected the tires and all looked OK at first, but about 12 hours later the TPMS went off. Reinspection showed a massive sidewall bulge on my right front tire. Interestingly, the tire hadn't lost too much pressure. I suspect the TPSM noted some small vibration.

So I put on the donut. FWIW if you do this, note that the plastic cylinder on the jack fits into a slot marked under you door jamb. And there is a clever plastic guide tool to slide your wheel on and off the hub (but keep reading a few pages in your manual - the instructions are all spread out). Thats a big big wheel - I had to redistribute the luggage quite a bit to get it in the trunk. Plus foul brake dust everywhere.

Unfortunately, it was Sunday, and the family was in no mood to hang around until late Monday. And the only place open was a Firestone. So off went all the OEM Contis (sad, with only 15K miles, but I believe conventional wisdom is not to mix tire tread or wear levels on a quattro). And on went 4 new Bridgestone Potenza RE960AS Pole Position (I have 18 in. rims). And they did inflate to max load (I did have 4 passengers + luggage). Thank goodness no dents or cracks in the wheel. So far, I can't say I'm discriminating enough to tell a difference between the stock tires (just my wallet). Drove 1000 miles home all good.