Tires on the Xi cars

[StigNV]

I have the sports package on an 08 335xi. Obviously it's a staggered configuration: 225's in the front and 255's in the back. Before I traded in my WRX, I had to replace a tire with a fatiging side walls, about 25,000 miles on the tread.
The rule of thumb is that all tires have to be replaced at the same time on a car with an AWD system. Trips to 5 tire dealers proved that point. However, my Subie had the same size tires all around.

Has anyone replaced tires on an Xi car yet, and did they have to replace all 4 tires if they were a staggered set? They can't be rotated, so it makes sense that you should only have to replace one in the scenario you destoyed the integrity of only one at lower mileage.

[mryakan]

Check this thread out:
http://forums.bimmerforums.com/forum/showthread.php?t=1013682

[landis]

My old car was an audi a4 and right in the owners manual it said to not let the tires be more than 2/32 different in diameter. This is because if the front and rears are a large difference in diameter it will over heat the center diff. So the type of center diff will dictates whether or not you can replace two tire at the same time. Since I haven't ever studied the xdrive system I can't comment on whether or not you need to replace 4 tires or can replace 2.