Take the tire pressures from the label on your driver's door jamb. If your tire size isn't listed, use the closest tire size.

Using nitrogen has no impact whatsoever on ride quality. Plain old air is mostly nitrogen in any case. All you get out of nitrogen is less chance of water (it is dryer), nice green valve caps, and a thinner wallet.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue