stream

I agree with the others--something doesn't seem right if you have significant understeer (there is a slight understeer bias in most BMWs).

Since you have the sport package, you car has active steering, and also active roll stabilization. ARS is an active stabilizer bar system, which does a great job of minimizing body roll, and until you get used to it, this may be contributing to the sense of understeer. ARS info here:
ARS.pdf

SolanNo1

Its either half empty or its half full

sdente

The problem is most likely alignment. I have an 05 545i with the sport package like yours. I have been able to get it setup with very good balance. The 5 series, like most cars, have been aligned to understeer by the factory. The factories do this for saftey (legal) reasons. Think about it. The proper driving input to correct for understeer is to move weight forward by lifting off the throttle, the correction for oversteer (not power induced oversteer) is to move weight to the rear by applying more throttle. When the average untrained driver enters a corner too fast and becomes frightened their natural instinct is to lift off the throttle to slow down. If the car is understeering, lifting off the throttle works in the drivers favor. If the car was oversteering, lifting off the throttle would worsen the problem and could lead to a spin. Even Porsche (known as oversteering cars) now aligns their cars to understeer at the factory.

I doubt that the problem is the run flats, my car also has them. Sure, they may have less overall grip, but it is the same compound at all four corners, so the car will be able to be set up with a proper neutral balance.

The first thing I do whenever I buy a new car is take it to the shop and have the alignment re-done. Most times the car never gets home before this is done. I have been driving race cars and testing for auto and tire manufactorers for over twenty years. Poorley balanced cars drive me nuts! Your 545i can be set up to be one of the best handling sedans on the road. Take it to a shop with BMW track experience to get it set up. The dealer will probably be limited to putting the factory alignment on the car.

jefferysf

The understeer seems to be intentional to protect the unskilled driver. Some correction can be had by ignoring the posted tire pressures. Try 40 all around... The culprit is the front-rear offset It's amazing anyone would buy a BMW based on a test drive with'stock" air pressures... Also,none of mine have had proper wheel alignment and NEVER has the steerting wheel been centered..not to mention the wheels that bend if you run over a tennnis ball
BTW the Pirelli Zero/Nero is a nice replacement for the PFTs

speedracerF4i

My $0.02 is as follows: (For non-US people, $0.02 means "My humble opinion")

1. Tires; The low temperature hardens rubber and reduces its coeficient of friction.

2. V8's Weight; The big V8 on top othe the front tires tend to widen your turn-arc. The extra 300 pounds over I-6 engines tend to enhance the feeling of understeer. The 530/525 feel much more tossable and nimble.

3. I don't know if you're in US, but if you're not, and don't have Active roll stabilization, then the pronounced roll may contribute to your sense of understeer.

4. Get different tires with more grip.

stubenhocker

You may want to check your tire pressure, as it sounds to me like you are carrying a rather large ego with you!

05E60Black545i

Hahaha