Nitrogen in tires?

[Low Note]

Originally Posted by JCL

I only have access to a 2009 owner's manual for the X6 5.0, so perhaps they have changed the recommendation. In that manual, over 100 mph sustained speeds, with four passengers, the recommendation for 19" tires is still 33/33. You have to go to the maximum gross vehicle weight (4 passengers plus a full load of luggage), and sustained speeds over 100 mph, to get up to 36/39 psi front/rear. You need all of those conditions, plus the 21" tire option, to get to 42 psi for a BMW recommendation. No worries, run them where you like, but I have never seen 33 psi cause cupping with any of my BMW vehicles, including those with RFTs. I have seen 39 psi and over cause accelerated wear in the centre of the tread.

On page 234 of the 2010 X5/X6 owners manual, it lists the recommended tire pressures with the stock 19" 255/50 R19 107 HM+S XL for speeds exceeding 100 mph as 41/42 front/rear. The ride at this setting is not at all stiff, and handling (with active steering) is amazing. My 2010 came with Michelin rft's, which may have something to do with the good ride quality. I asked the head master mechanic (Todd Thomas, who is rated by BMW as one of the ten best in the USA) at my dealer, SunMotorCars BMW about the possibility of this setting causing premature center tread wear, and he said that this should not be a problem. In fact, he strongly suggested running with the 41/42 for best tire life. So far, so good.

BTW, for what it's worth, I find the active steering option to be amazing. There has been a lot of negative stuff flying around about BMW's active steering, but once I drove my new X6 off the lot, there was no doubt that i made the right choice. The 2009 X6 that I test drove (at another dealer) did not have active steering, and even with the 20" performance tires, did not handle nearly as well.