Big tyres on the back and small tyres on the front, the back pushes the car straight ahead because there's not enough rubber upfront to turn the car into corners, putting it a simple way.
There are other factures such as the weight of the front car, HP generated at the back wheels, Locker diffs, suspension setup, alighment etc.
But 245's onthe front is little to small for a M3 V8.
I am sure someone will give you a 1000 word technical discription of the above should you require a more detailed version.
X5 F15 M50d White, 20"rims, Yellow Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, otherwise all option boxes are ticked.