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[Fyre4ce]

My 2008 E90 335i doesn't have the sport package (225/45R17 stock tires), but a couple years ago when he needed new tires I upgraded to the 59615/59621 18" OEM wheels and Continental ExtremeContact DW tires (225/40ZR18 front, 255/35ZR18 rear). I used the inflation pressures that are listed on the door jamb sticker (32psi front, 38psi rear) despite being different wheels and tires, although as a matter of practice I usually overinflated by a couple psi, because I don't frequently put air in, and this way my average is closer to spec.

30k miles later, the tires need replacement, although the wear on the front is more on the inside and outside, and the rears are more worn in the middle and less on the sides. Seems obvious that the fronts needed more pressure and the rears less, although I'd like to find out how much. Is there a way to look up the factory pressures for the 335i with the sport package? Or, maybe some tire guru from TireRack or elsewhere is able to estimate what pressure changes are needed based on the wear (eg. if the middle wears X% faster than the edges, then lower pressure by Y psi). Without any new data, my plan is to start with 34 front, 36 rear, and measure with a tread depth over the first year. If there's any uneven wear starting I can adjust while I still have time.

I'm replacing the Continentals with Michelin Pilot Sport 4S's, same size, and they have the same load rating, so I'd expect the load/pressure behavior to be similar.

Thanks in advance!

Update: I realized the manual lists inflation pressures for all configurations. There are two listed for the 255/35R18 rears, 35 and 38, but the question of how to estimate needed pressure changes based on wear remains.