BRAKE PERFORMANCE

 

 

INFORMATION

 

VEHICLES NOT TO BE TESTED ON A ROLLER BRAKE TESTER

 

• Vehicles with brakes for which the servo operates only when the vehicle is moving.

 

• Vehicles with 3 wheels

 

• Motorcycle based Quadricycles

 

These vehicles should be tested using a properly calibrated and maintained decelerometer, see Sub-Section Decelerometer Test.

 

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

 

Certain vehicles may not be suitable for testing using a roller brake tester. Examiners should take account of the vehicle’s drive configuration, transmission type and any Vehicle Specific Information before deciding whether a full or partial roller brake test is appropriate.

 

Note:

Vehicles with more than 2 axles should only be tested on the Heavy vehicle test lane.

 

AUTOMATIC TRANSMISSION

 

Vehicles with automatic transmission must never be roller brake tested with the gear selector in the “P” park position. ‘N’ Neutral must always be selected before conducting a brake test.

 

SERVO-ASSISTED OR POWER BRAKES

 

For vehicles with servo assisted or power braking systems, the engine must be idling while the service brake is being tested.

 

Note:

With a veteran car or a vehicle with special controls, special care should be taken to ensure no damage is caused to the vehicle.

 

VEHICLES WHICH ONLY JUST PASS

 

With some vehicles, the required brake efficiency is just obtained or just exceeded, but the examiner knows that a higher performance figure is normally obtained for the type of vehicle. Although the vehicle has passed the brake performance test, the examiner should advise the vehicle presenter that the braking system appears to need adjustment or repair.

 

 

 

 

BRAKE EFFICIENCY TABLE

 

		CLASS OF VEHICLE		MINIMUM BRAKE EFFICIENCIES REQUIRED
				SERVICE BRAKE		PARKING BRAKE
						Vehicle with a single line braking system		Vehicle with a split (dual) braking system
1		Vehicles with 4 or more wheels having a single service brake (foot-brake) operating on at least 4 wheels and a parking (handbrake) operating on at least 2 wheels. Excluding vehicles in item 4 of this table.		50% or 58% for M1 vehicles first used on or after 1 January 2012   (M1 - Vehicles used for the carriage of passengers and comprising not more than eight seats in addition to the driver's seat)		25%		16%
2		Vehicles with 3 wheels with a single service brake operating on ALL wheels and a parking brake operating on at least one axle which were first used:   I before 1 January 1968		40%		25%		16%
		ii on or after 1 January 1968   Excluding vehicles in item 4 of this table.		50%		25%		16%
	3		Vehicles first used before 1 January 1968 which do NOT have one means of control operating on at least 4 wheels (or 3 for three wheeled vehicle) and which have one brake system with two means of control or two brake systems with separate means of control.		30% from first means of control		25% from second means of control
	4		3 wheeled moped or light quadricycle with single service brake control operating the brakes on all wheels.		40%		25%		16%
	5		3 wheeled moped, light quadricycle, motorcycle based tricycle or quadricycle with 2 service brake systems each having a separate means of operation.		30% from either system and 25% from other system (secondary system)		N/A		16%
	6		Vehicles first used before 1 January 1915		One efficient braking system required

 

NOTE:

16% parking brake efficiency equates to a vehicle holding on a gradient of 1 in 6.25.

 

METHOD OF INSPECTION

 

ROLLER BRAKE TEST PREPARATION

 

 

1. Examine the tyres of the vehicle to ensure that they are not obviously under-inflated.
2. Determine whether the vehicle has a split (dual) braking system.

Note:

To determine whether the vehicle has a split (dual) braking system, check the number of pipes from a hydraulic master cylinder or air foot valve. Split (dual) systems normally have at least 2 pipes. Some hydraulic systems have 2 master cylinders.

 

3. If four wheel drive or differential locks are fitted to a vehicle, ensure all are disengaged.
4. Normally the direction of rotation of the roller brake testers will be set so that the vehicle wheels rotate forward. It is important to note that damage can be caused to vehicles with certain types of differentials, if the rotation of the rollers are in the opposite direction. e.g. Limited slip differential

 

POSITIONING THE VEHICLE

 

Drive the vehicle sharply over the Side-slip tester onto the Shock absorber test plates. These plates not only test the shock absorbers but also weigh the vehicle’s axles, which allows the equipment to later calculate the brake efficiency. When the shock absorber test is complete, position the front wheels of the vehicle in the rollers of the brake tester, then both sets of rollers will run together, aligning the vehicle. Allow time for vehicle to align on the brake rollers, after several rotations of the roller apply the park brake (if operates on rear axle). This will help to retain the vehicles front wheels in the rollers to achieve maximum brake force.

 

Note:

The park brake should not be applied on vehicles fitted with a four wheel drive system to retain the vehicle’s wheels in the brake rollers.

 

TESTING THE BRAKES

 

1. Follow the instructions on the screen. Gradually depress the service brake until appropriate effort is achieved for ‘brake ovality’ to be tested. When the ovality test is complete further depress the service brake slowly and observe the rate of brake force increase, then gradually release the service brake and observe the rate of decrease. During this process also watch for brake imbalance, grab and judder. Then apply the service brake until maximum brake effort is achieved or until wheel lock occurs. Release the service brake.
2. The brake tester will automatically switch to the parking brake mode when wheel lock occurs. If the vehicle has a parking brake (handbrake) which operates on the front wheels and wheel lock was not achieved on the service brake. Drive the vehicle forward until the front wheels are out of the rollers and then reverse back into them. This will switch the system to parking brake mode. Both brake rollers will start to rotate, apply the parking brake, keeping the “hold-on” button or trigger in the disengaged position the whole time. As the brake is applied one of the brake rollers will stop and each brake will be tested individually. When wheel lock occurs the brake roller will stop and the other one will start. Apply the hand brake again in the same manner and when wheel lock occurs the results will be stored. In the case where wheel lock was not achieved a timer will count down and after 10 seconds the highest brake readings will be stored.
3. If the vehicle has a parking brake (handbrake), which operates only on the rear wheels. Drive the vehicle forward, the rear axle will be weighed on the shock absorber plates. When the shock absorber test is complete on the rear axle, position the rear wheels of the vehicle in the rollers. The parking brake was not tested on the first axle, therefore the brake tester will test the parking brake on the rear axle before testing the service brake. Both brake rollers will start to rotate, apply the parking brake, keeping the “hold-on” button or trigger in the disengaged position the whole time. As the brake is applied one of the brake rollers will stop and each brake will be tested individually. When wheel lock occurs the brake roller will stop and the other one will start. Apply the hand brake again in the same manner and when wheel lock occurs the results will be stored. In the case where wheel lock was not achieved a timer will count down and after 10 seconds the highest brake readings will be stored.
4. When the parking brake test is complete, the brake tester will automatically change back to the service brake mode. For the service brake test on the rear axle, repeat process outlined in 1 above.

Note:

Test results are recorded when wheel lock is achieved, when the vehicle is driven out of the brake tester, or in the case of totally defective brakes on an axle when a predetermined time has elapsed. The rollers must be rotating before leaving the brake tester.

 

TESTING TRANSMISSION (PROP SHAFT) PARK BRAKES

 

Carry out the following procedure:

 

• The system is set to default to the brake mode that tests the handbrake on individual wheels therefore select the brake test mode that tests both wheels together.

 

• Keep the handbrake ratchet disengaged for as long as the brake is applied.

 

• Apply the brake slowly and progressively without causing transmission snatch.

 

Note:

A transmission handbrake fitted to a permanent four-wheel drive vehicle can not be tested using the brake roller tester.

 

 

PERMANENT FOUR WHEEL DRIVE

 

1. Before entering the brake tester rollers, select the 4WD program which will change the direction of the roller rotation, so that one will rotate forward and the other backwards.

Note: The park brake should not be applied to retain the vehicle’s wheels in the brake rollers.

2. Follow the previous procedure, ‘Testing the brakes’. However, note that each brake will be tested separately. The brake test equipment will only record results for the wheel, which is rotating forward.
3. When the brake on the first wheel has been tested, stop the rollers and change the roller rotation to the opposite direction. Conduct a brake test on the other front wheel.
4. Drive the vehicle forward and repeat the above procedures for the rear axle.

Note:

It is very important that the examiner ensures that the brake roller rotation and program is returned to its normal setting before proceeding to stage 4.

 

ELECTRIC AND HYBRID VEHICLES

 

1. Before commencing the brake test, activate the brake roller lock switch located on the brake tester cabinet;

 

2. Take the remote control for the brake tester as this may be required;

 

3. After conducting the brake test on an axle, the rollers must be stopped to allow the brake roller lock to engage before driving out of the brake tester;

 

1. 1. If the brake rollers do not stop e.g. brake force not sufficient to cause the brake rollers to stop, or if they have restarted, the brake rollers must be stopped using the remote control devise.

 

1. 2. With the rollers stopped, the roller lock will only be active for a few seconds allowing the vehicle to be driven out of the rollers. If the examiner delays driving out of the rollers the lock will automatically disengage within a few seconds. In this case the examiner must restart the brake rollers using the remote control device and then stop all rollers again with the remote control device before driving out of the rollers;

 

4. After completing the brake test on all axles driving out of the brake rollers, store results, deactivate the brake roller lock switch located on the brake tester cabinet and return the

remote control device to its terminal.

 

REASON FOR REJECTION

Deficiency Category