I have 18mm Velocity spacers and lowered my X5 with H&R lowering kit. Both of which increase negative camber. I have negative camber set at the max. but still in spec. I run performance tires year round. Rears last about 7,500 miles. Front twice that. Would be great if I got more miles out of my tires but I wouldn't own it if it handled like other SUVs.

Life cycles of front and rear moving components are similar enough that replacing some can result in an in spec alignment but it won't be long before that can't be done due to other associated failures. Generally, new stuff accelerates wear on old stuff.

Acceleration compresses the suspension increasing negative camber but if the alignment is in spec that should not result in excessive inner tire wear.

Tires can easily be the only problem. Be sure that somewhere along the line you didn't go to a softer tread. Look for tires with tread hardness in the 400 range if you want tires to last longer.

FYI, if anyone is reading the old portion of this thread there are some posts that are completely false even ludicrous.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas