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I inflate to 45psi cold on 20" M-B wheels. M-B recommends mid-30s which causes uneven tire (shoulder) wear. I air up my wife's G01 X3 tires 5 psi higher than BMW recommends. I don't recall the specific value in psi at the moment.
Carmakers are wishy-washy about tire pressure. Lower pressure generally gives better ride quality and avoids complaints, especially with harsh 20" and 21" wheels these days. There is no escaping the harshness with larger wheels, even more so when the tires are runflats. The downside of low inflation pressure is poor tread life.
M-B calls for excessive, in my opinion, rear camber and toe settings, and this also plays into tire wear, in concert with inflation pressure.
Airing up well beyond manufacturer specification, as I do, maximizes tread life with an unnoticeable change in ride quality. 20" and 21" wheels are harsh, no matter what inflation pressure is chosen.
On your 7 series, if you want maximum tire life, air up to at least 45 psi, or 50 psi. If you want maximum comfort, keep the pressure in the mid-upper 30s and watch the shoulder wear appear after about 10k-15k miles.
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