Park brake only just met - How tested

How many times now do you test a vehicle that the government say should have 58% service brake efficiency but after the roller brake test you click the button and fail appears!! You look back at the readings and understanding before you decide nothing is wrong so you lock out a third wheel and pass it.

We've had long discussions on this subject over years and I did explain out the full requirements about test weights, vehicle weights and decelerometer brake testing. 

In laymans terms comparing a gradient test to a roller brake test is not reasonable. If the vehicle under test has discs and calipers, then a high clamping force is required to get a good brake effort, however, on the other hand, if a drum brake assembly is being tested, then the self rapping action of the leading shoes will bite into the drum giving a much better brake effort. Now if you put both types of brakes on a gradient test, the drum brake assembly will fare better because of the self rapping action, where as brake pads without a high brake force applied will slip. 

On a roller brake test the operator must have an understanding of the roller motor itself. When a load is applied to a motor, the motor itself does not slow down, it draws more current and demands the wheel is turned, which means any brake defect will show up easier on a roller brake test, whereby a gradient test could pass a worn defective operating brake system.