That’s the reminder from traffic commissioner Kevin Rooney, who says details on a roller brake test report could indicate a defective component or impending failure.
In addition, he points out, roller brake tests only assess the capability of a braking system in the test conditions. “If you test a vehicle empty, then load it – the braking system’s being asked to deliver much more when it’s carrying that load.”
DVSA’s guide to heavy vehicle brake testing (see link below) says that axles should be loaded to at least 65% of their design weight for testing.
Trucks, and particularly trailers, adds Rooney, can have “very dramatic” laden to unladen weight ratios – 3:1 is common for a tractor unit and 5:1 is not unusual for a trailer.
If the wheels are locking out early – well before the expected performance figures have been reached, even for buses and coaches – Rooney recommends some form of additional loading for a worthwhile brake test.
Keep brake rollers well gritted and dry to ensure a good test, he says, and ensure test results are fully analysed, in particular investigate if figures are unusually high or if one vehicle is performing differently to others in the fleet.
Also, see Transport Engineer’s next issue (May) for a feature on brake testing.