Summer tires
Do not drive with a tire tread depth of less than 0.12 in/3 mm.
There is an increased danger of hydroplaning if the tire tread depth is less than 0.12 in/3 mm.
Winter tires
Do not drive with a tire tread depth of less than 0.16 in/4 mm.
Below a tread depth of 0.16 in/4 mm, tires are less suitable for winter operation.
Minimum tread depth
Wear indicators are distributed around the tire's circumference and have the legally required minimum height of 0.063 in/1.6 mm.
They are marked on the side of the tire with TWI, Tread Wear Indicator.
BMW X3 Service & Repair Manual > Electrical components/wear indicator: Replacing a brake pad sensor (front)
IMPORTANT:
The brake pad wear sensor must be replaced once it has been removed (brake pad wear sensor
loses its retention capability in the brake pad).
If an already ground brake pad wear sensor has to be replaced although the minimum brake pad thickness has
not yet been reached, it is ...