Originally Posted by MikeyXR2i
Im sure when the cars in the 1 set of rollers, the car is in neutral, so the 4x4 system won't be engaged. Then he just presses the brake and watches his readings.
noooo!
the 4wd is permanently engaged, rear wheels are linked to the front by the centre diff and viscous coupling.. if you try and drive one pair of wheels without the other you will risk damaging the centre viscous coupling. Although Ford quote that it's ok provided the wheels aren't driven over 5mph for 30 seconds, it's much better not to do it at all.
They will normally put a Tapley meter in the footwell and drive the car on the road to test the brakes. The Tapley uses g-force to measure braking retardation.
The Tapley Brake Testing Meter
The Tapley Brake Testing Meter is a pendulum-type decelerometer especially designed for convenience of use in motor vehicles on the road. It is accurate and robustly constructed to give long operational life. No special skill is required for its use and reliable results can be obtained with it by following simple instructions.
The meter has only three principal working parts. A heavy pendulum is pivoted at the top so that normally it hangs vertically inside a box which is filled with special oil to damp the movements of the pendulum so that vibration does not affect the indication given. The pendulum is a powerful permanent magnet and when it moves, a light armature follows its movements exactly.
The armature is joined to a toothed segment which in turn drives a pinion to which is connected the circular scale. The scale is read through an opening in the top of the casing and a light ratchet retains the scale at its maximum displacement. The whole mechanism is mounted in a casing carried on pivots which incorporate a fine adjustment so that the casing can be set level before a test. The pivots in turn are mounted on a heavy metal block.