Unless one is racing (and I assume knows what tire pressure to use), then it
is always a safe bet to use 30 psi on all four corners until one can find
out what the actual pressure should be. I see no reason to sway from 30 psi
until the sidewalls get very narrow.
I had the 225/55x15s on my 3 Series, and switched to the same tires the OP
is asking about. I use 30 psi, and they are fine. I'll accept an argument
that says 29 front and 32 rear, but I don't think that a pound or two is
going to change very much in the grand scheme of things.
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