Are these XL tires?

I was wrong, when I looked at my tires this morning it says 50 psi max. Not sure where I got 40 psi :dunno:

They are Pirelli SCORPION VERDE ALL SEASON RUN FLAT 255/50R19 107H XL. I just looked them up in Tirerack and here what it says:

"XL/RF tires required if 255/50-19 is used on rear axle. This requires higher tire pressure levels of 42psi for proper load."

I inflated to 40 psi all around this morning, should I go with 42 in the rear?

Yes, 255/50R19 107H XL.

SO there is a maximum load that is specified by BMW... and to achieve THIS load, you should inflate the tires to the max pressure ON THE DOORJAMB PLACARD.

This can be independent from the maximum load for a given tire, and the inflation pressure to achieve that load.

My recollection is that you do not need to run tires at 50, 51, whatever to hit your maximum load rating that BMW states the car can handle. (and presumably BMW has determined 'at a fully laden configuration, the rear axle sees XXX lbs and therefore needs YY psi'.) And both of these numbers are UNDER the max tire load rating and max PSI ratings

So two different things... Correct?

There is some pretty basic math to get even tire patches. I was curious so I did the math for my car.

My car typically weighs in as 1200# front corner and 1600# back corner (2400+3200=5600).

When loaded like I drive BMW recommends 32# front 39# back.

That works out to 1600/39=41 in.² patch rear and 1200/32=37.5 in.² front. Very close. To get them equal would take 1600/37.5=42.667 psi which I'm betting BMW did their homework and figure out it's best to let the back patch be bigger.

I get perfectly even tire wear and superb car-like handling. (cheat a little bit with $300 winter tires year 'round).


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But WHY is this 'better' for BMW?

To give them a car that plows like a dog with horrible understeer so soccer dads cant get into trouble?

Or to set up the X5 as a world class driving machine??


:cool:

The second. my car drives like a car even when loaded with 1000# of tools.

Yes, two different things.
I'd like to think that BMW did the calcs as you describe, but my gut tells me the lawyers were also involved to prevent oversteer. My point was that tire mfr's have a recommended pressure to achieve the tire's load rating and that BMW's pressures aren't even close to that limit. Virtually all of the 13 Bimmer's I've owned need 4-6 psi higher pressure than shown on the B pillar to get uniform front tire wear.

You must drive like an old woman....... :rofl:

Woof, woof...........