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Old 10-04-2009, 03:25 PM
vrooom3440 vrooom3440 is offline
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Location: Granite Bay, CA
Join Date: Sep 2009
Posts: 56
Mein Auto: 330i/X3/El Camino
Tires changed on only one side would make me wonder about why those tires were replaced... typical scenario is accident damage.

It is interesting to note how Xdrive works here... you have full floating differentials front and rear. That means within reason there is no detrimental affect from different sized wheels side to side. A limited slip diff with slipper clutches would have issues with different sizes but that is not how BMW Xdrive is built.

In the middle there is a clutch but it is probably not engaged normally. The whole deal is driven off the ABS wheel sensors and computer. If one or more wheels turns at a rate significantly faster by some margin, then Xdrive makes corrections. This is where it would engage the center transfer case clutch. But the main thing it does is apply brakes on spinning wheels to limit wheel spin and thereby direct more engine torque into other wheels. Brakes do not care much about different wheel sizes.

Likewise since the sensor process is individual per wheel it matters not if some tires are better than others. The computer just adjusts based on conditions. So I would not worry too much about new tires on just one end versus the other.
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