My 3.0d does that too - a few times I've been concerned enough to actually get out a gauge and check the pressure, as the front tyre bulge looks very alarming. It's acerbated by the level of the ground it seems...

But they are fine. I have always run 32/32 but have gone to 34/34 on the new tyres I've just fitted as the sidewalls seem slightly softer than the older tyres I had on.

Hey wpoll all good? Yup when i park one side on a kerbside and look at the tire on the side of the road taking the weight i always think i am nearly flat....as for my slow air leak gonna give it few days and see....aint rocket science i will locate the loss eventually

For handling purposes, when aligned properly, x5s, for that matter all BMWs, will have enough negative camber to wear the inside of the tires, especially the rears. Some align for little or no negative camber to correct the inside wear. Reducing negative camber reduces handling limits and regular driving characteristics, one may or may not care. Significant over inflation might offset some of negative camber wear though there will be a noticeable change in ride quality.

Tires that are the correct size for a vehicle can have different specs for sidewalls and tread, softer or harder. Soft sidewall tires can appear under inflated when they are not. The wear pattern can change due to under inflating. Over inflating, unless extreme. does not, though it will reduce handling limits and regular driving characteristics. The impact of correct, over or under inflation varies by driving style and outside temperature.Over inflation can improve mileage.

Unless one is loading the back with a ton of bricks and driving across country there is no need to adjust inflation. Depending on the tongue weight of a trailer, increasing the rear tire pressure will help if the trailer starts swaying.

Over the years of ownership, I have purchased several different brands and model tires. If or how I adjusted inflation varied. There is no constant set of parameters, no one 'size' fits all certainly not from one X5 to another. I align to the max negative in spec degrees and accept the tires will always wear out on the inside.

I run Michelin Latitude Sport 3 in the summer, 255/50 R19 + 285/45 R19; Nokian Weatherproof SUV 235/65 R17 in Winter. Usually just me in the car, 32 psi all round.