Tire replacement question - not about rotating

[lowpost]

I bought my car used and only 1 rear tire seems to be almost bald. The other 3 still have about 6-9 months on them. My tire shop tells me that since it's all wheel drive I need to replace all 4. Seems excessive to me. Considering I'm not racing my X5 like an M5, I think only replacing the rear 2 should be fine. What do you guys think?

Also I wanted to switch to the Pirellis - if I only do the 2 rears, think that will matter that much?

Thanks!

[xnsf]

I guess you can expect to have a staggered tire replacement schedule...

shouldn't be any problem...