Some drivers like a little underwater, some neutral and some love oversteer. There's a lot of personal preference in handling characteristics. Personally I prefer a just a little oversteer. But, doesn't matter much what it does unless your are pushing the handling limits. The X5 suspension is not designed for oversteer and I think handling limits will be compromised if you can find a setup that results in oversteer. You mentioned the tire question is for the 2003. If that is your 4.6 it should have 20 in staggered rims. Over the years I've tried many different combinations. I have always gone through two pairs of rears to one pair of fronts. Most of the time even when changing brands I only buy the two I need. Tread wear differences are not an issue if you are staying with OE sizes. Currently I'm running Continental Extreme Contacts. Very close to the best handling tire but certainly best all around tire I have run. That's based on ride quality, handling, wear and price.

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