BMW F10 xDrive tyre sizes and wear
Do the tyres on an xDrive car have to be the same size front and rear?
What matters most is that the rolling circumference is as equal as possible front and rear. Four-wheel-drive cars have come from the factory with different widths and profiles on the same circumference, for example 245/45-18 and 275/40-18. Even a small difference strains the four-wheel-drive system.
Can I put a wider tyre on the rear than on the front?
Yes, if the difference in rolling circumference stays under 1 percent. The width itself is not a problem, because the circumference stays the same. The wear difference between same-size tyres should be kept small, about 2 mm, otherwise rumbling may be heard.
What causes uneven wear on the front tyres?
The cause is usually the alignment and angles, which are affected by loose suspension parts and a worn shock absorber or spring. Check the suspension play before a four-wheel alignment. If the tyres are very worn, buy new ones only after the angles have been adjusted.