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I'm running a BMW X1 AWD Xdrive with OEM 19" wheel spec staggered:

255 / 35 / 19 Rear 225 / 40 / 19 Front

Staggered tires height difference is -0.06" (approx 2/32", back tires have less height, I used https://www.discounttiredirect.com/learn/tire-size-calculator)

Tires are BFG G-force comp 2 A/S. When new, they are ~ 9/32, they have less than 10k miles.

I noticed that my rear tires wear in the middle is already 6/32 and ~7/32 on the sides. Front tires wear is 8/32 (!!) and a bit more than 7/32 on the sides.

It's my understanding that BMW cars are rear wheels bias, so even with Xdrive/AWD, the rear almost always wear first, specially in the center (due to quick acceleration and spirited driving).

QUESTION:

Should I keep running these until rear tires are 2/32 and change all 4, or I should change my rear tires already? I know that it's generally recommended to change all 4 tires on AWD, but since my front tires are almost new, and that that the rear is already -.06" height due to the staggered setup, I thought maybe I could start the next summer with brand new rear tires (currently running winter tires).

I'm afraid the rear tires continue to wear too fast, creating more than 1% of diff., which could maybe hurt the transfer case.

I would also have my current rear tires as good backups (since they are 50% used).

Thanks!

  • The xDrive system uses an electronically controlled wet clutch rather than a conventional diff in the transfer case, and gives a 60:40 bias towards the rear in normal circumstances. I don't know how that would be affected by the difference in diameter though, compared with a conventional setup – Nick C Nov 15 '17 at 15:51

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