[shellbmb]

I noticed the stock 21" tire size is 285/45/21, and I think the 22" option is a staggered 275/40/22 and 315/35/22.

I'm coming from owning a 2009 and 2014 MB GL550 with the 21" tire option and I will tell you they have been a royal PITA. You have very limited options and the options they have aren't the best. Plus, the camber settings on the GL are very aggressive leading to premature inside wear on the tires. Now don't get me wrong, I love the GL, but the tires have been my biggest complaint.

A cursory look for tires in the 285/45/21 size aren't all that impressive. You either have a max performance summer tire with a treadwear rating of 220-240 (those would last long) or Pirelli Scorpion which performed very poorly on the GL.

The only tire I can find in a 315/35/22 size is the new Pirelli P-zero run-flat. It also comes in a 275/40/22 so I'm guessing that is what will come on the X7 with the 22" option. Some of the pictures have also shown a Conti in a 22" so I guess they'll have an option as well. But with a staggered fitment, you can't rotate them so it will be interesting to see how they wear.

I'm hoping once the X7 hits market, we'll see some other tire options pop up. But I would factor in tire selection/availability as a decision factor between 21 and 22. Right now it doesn't look like there is much selection in either.

On my GL's, I've seen a life span of 15-18k miles.