Quote:
Originally Posted by mibmwx3
The fronts are 32 psi, one rear is 34 psi and the other 30 psi, so looks like I'll need to add some air. I also noticed that the caps are lose and spin around. I don't remember that they did that before. Are they one size fits all and just not attached securely?
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That's exactly what I mean about not trusting dealers to set the tire pressures correctly! Having only 30 psi in a rear X3 tire is almost criminal.
Remember to reset the TPM system (use iDrive and then drive the car) once you have the tires set to the correct pressures (cold).
What size winter tires did you purchase?
The factory spec for your summer 245/45R19 size is 32 (F) and 38(R). I'd try 35psi (F) and 41psi(R) as a starting point. If the ride is "too hard" for your taste, you can drop it a few psi.
If your winter tires are a different size, the optimum pressures will also be different.
If your tires have the standard small plastic valve caps, they should be turned clockwise until they are finger tight. If they continue to turn and don't tighten, the caps are stripped. It's easy to do if they are overtightened. You can replace them at any auto parts store. There is only one size for the "Schrader" valve caps. The size was standardized in 1893 in the US and has become one of the longest lasting standard parts on cars worldwide.
BMW recommends using only plastic caps, because metal ones can corrode if not maintained properly. I use theft-proof chrome plated brass caps, but check pressures each month and can lube the threads if they look like they need it.