Over inflation is a sure sign of center tread wear. Note: driving with one occupant with big fat rear tires and following the recommended inflation as marked in the owners manual and door jam will give you the results you are experiencing with a 4.6 and a 4.8is with 315 width tires. Tire foot print is based on tire width, rim size, and weight on at the wheel. Ignore those who post high numbers as they are running skinny tires on the 6 banger or 4.4 applications.

I run approx 32 psi in the rear after burning through two sets in 20k. These things weigh in at 3600# and will burn off Hugh amount of tread on hard acceleration runs.

Note 2: if you are planning hard runs with lots of hard acceleration out of turns, then bump the rears to 36 psi to keep the tire planted.

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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green