The M.O.T. Inspection Manual Issue Date 01 January 2012                                                                                                                                1.  Brake Efficiency (Class 5) The brake efficiency will be calculated by the VTS Device using the following methods (having taken into account wheel lock where appropriate). Total up the braking effort recorded from all the wheels of the vehicle when the service brake is applied. Total up the braking effort recorded from the appropriate wheels when the parking brake is applied. The service brake and parking brake percentage efficiencies may be calculated by using the procedures detailed below. Service Brake Efficiency Calculate the service brake percentage efficiency by dividing the total brake effort achieved when the service brake is applied by the lesser of the vehicle’s DGW or MAM and then multiplying the result by 100.   Parking Brake Efficiency Calculate the parking brake percentage efficiency by dividing the total brake effort achieved when the parking brake is applied by the lesser of the vehicle’s DGW or MAM and then multiplying by 100. Total service brake effort Total parking brake effort i.e. DGW/MAM X 100 = % Efficiency i.e. DGW/MAM X 100 = % Efficiency The DGW/MAM is normally shown on the manufacturers’ plate.  Where only the unladen weight   is shown on the vehicle, calculate the DGW/MAM as follows:    [Number of passenger seats (excluding the driver’s seat) 63.5kg (or 140lbs)] unladen weight X + 2.  Brake Out-of-Balance The out of balance of the braking effort on the front steered wheels when the service brake is applied is obtained by comparing the brake efforts at each front wheel when they are tested simultaneously (see sub-section 3.7.A2).  Carry out the following calculation to determine the percentage imbalance: (Higher brake effort  -  Lower brake effort) Higher brake effort X 100 = % Imbalance 3.8 Method of Calculating Brake Performance (Class 5 only)