The concept
The parking brake is primarily intended to prevent the vehicle from rolling while parked; it brakes the rear wheels.

See also:
Braking: One Step Up, Two Back
There is an aspect of the 5 Series that we do object to, though, and that's
the braking. To be clear, the car stops well enough; it's not a safety concern.
The problem is the feel of the braking, ...
VALVETRONIC, Double-Vanos and direct injection
The combination of a high power output and a simultaneous reduction in
emissions is achieved by VALVETRONIC variable valve timing and Double-Vanos
variable camshaft timing. The latest generation o ...
2010 BMW X5 Review
Aside from a low clatter at startup, there are few initial signs that BMW's diesel-powered X5 is a different sort of beast. Drive it you must, though, because diesel power is addictive. As is the ca ...
