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Certain vehicles should not be tested on a roller brake tester, eg vehicles with More than one driving axle permanently engaged Limited-slip differential Belt-driven transmission Brakes for which the servo operates only when the vehicle is moving These vehicles should be tested using a properly calibrated and maintained decelerometer or a plate brake tester designated as acceptable for the statutory tests, see Sub Section 3.7 B, page 24, and C, page 25.

A roller brake test is also not appropriate for vehicles with damaged, under-inflated or studded tyres.

3. Select the direction of rotation of the roller brake testers so that the vehicle wheels rotate forward. Positioning the vehicle Position the front wheels of the vehicle in the rollers of the brake tester and then run both sets of rollers together to align the vehicle.

Note: In some cases, it may be necessary to chock the wheels not under test.

2. Start both sets of rollers and note whether a significant brake effort is recorded from any wheel without a brake being applied.  Gradually depress the service brake and watch how the braking effort for each wheel increases.

From the previous tests you will know the value at which wheelslip occurs.  Aim to stop just short of this. However, if wheelslip is caused unintentionally, start the test again. Gradually release the service brake and observe how the braking effort at each wheel reduces.  Stop the rollers.

Note the out-of-balance in braking effort between wheels on either side of the vehicle

e. The out-of-balance of the brakes on the steered road wheels is greater than 25% at any time (see Method of Calculating Brakes out-of- Balance on page 26)

Note: Disregard any service brake imbalance when the brake effort from each front wheel is less than 40kg

5. Start both sets of rollers and note whether a significant brake effort is recorded from any wheel without a brake being applied.  Gradually depress the service brake and watch how the braking effort for each wheel increases. From the previous tests you will know the value at which wheelslip occurs.  Aim to stop just short of this.

However, if wheelslip is caused unintentionally, start the test again.

5. 

a. A significant effort recorded on a roadwheel, even though the brake is not applied indicating that a brake is binding

7. If the vehicle has a parking brake (handbrake) which operates on the rear wheels, repeat the process as outlined in 3 above using this brake and keeping the “hold-on” button or trigger in the disengaged position the whole time.

Note: For testing transmission (prop-shaft) handbrakes, see page 23.

7.

a. A low braking effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly  

8. The calculated service brake efficiency is too low (see Brake Efficiency Table on page 28)

Note: The service brake percentage efficiency is considered satisfactory providing wheel lock occurs on more than half of the wheels braked by the service brake.

Note: Class VII vehicles only 

When testing service brake performance on unladen vehicles Premature wheel lock can occur, and Less than the required brake effort is achieved

The required brake effort might not be achieved due to the action of load sensing/pressure reducing equipment in the service brake system.

In either of these cases, the service brake percentage efficiency is considered satisfactory if

i. more than half the wheels lock, or

ii. both front wheels lock and at least 100kg (220lb) is achieved by each rear wheel, or 

iii. for three axle vehicles; both front wheels lock and at least 50kg (110lb) is achieved by each rear wheel

Roads used for decelerometer brake testing

The requirement for a steady road speed during a brake test by decelerometer means that the vehicle must always be driven on a road which Has a good surface Is suitable for brake tests when dry or wet Has a minimum of traffic

A particular public road should not be used for tests so much that it would cause complaints from residents.

C. Plate Brake Test Preparation

1. Determine whether the vehicle has a single or dual (split) braking system.

Note: To determine whether the vehicle has a dual (split) braking system, check the number of pipes from the hydraulic master cylinder or air foot valve.  Dual (split) systems normally have at least two pipes.

Some hydraulic systems have two master cylinders.

With some vehicles, the required brake efficiency is just obtained or just exceeded, but the tester knows that a higher performance figure is normally obtained for the type of vehicle.

Although the vehicle has passed the brake performance test, the tester should advise the vehicle presenter that the braking system appears to need adjustment or repair.

2. Class IV vehicles: Obtain the vehicle test weight from the data chart.

Class VII vehicles: Establish the vehicle actual presented weight.

The brake efficiency on class VII vehicles will be calculated using either:

the actual DGW where the presented weight is 2000Kg or over (the DGW is obtained from the Department or Transport plate or the manufacturers plate fitted to the vehicle – see notes 1 and 2 on page 27), or

a nominal DGW figure of 2600Kg if the presented weight is less than 2000Kg.

2.

a. a significant brake effort recorded on a roadwheel, when the brake is not applied, indicating that a brake is binding

Note. The way in which the brake efforts increase . The maximum values achieved.

c. the out-of-balance of the brakes on the steered roadwheels is greater than 25% at any time

Note: Disregard any imbalance when the brake effort from each front wheel is less than 40Kg force