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The Testers Manual

3.7 Brake Performance (Roller Brake Test)

Information	Method of Inspection	Reason for rejection
A. Roller Brake Test
The brake performance test must be carried out on a properly calibrated and maintained slow-speed roller-brake tester designated as acceptable for the statutory tests, except Vehicles for which a roller brake tester is not appropriate, or At premises without a roller brake tester where approval has been granted for the test to be carried out by other means	If the vehicle is of a type which can be tested on a roller brake tester
Vehicles not to be tested on a roller brake tester
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 25, and C, page 26. A roller brake test is also not appropriate for vehicles with damaged, under-inflated or studded tyres.	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 two pipes. Some hydraulic systems have two master cylinders.
	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.
Automatic transmission
Vehicles with automatic transmission must never be roller brake tested with the gear selector in the “P” park position.
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 the driver should be allowed to drive during the test, if he/she wishes. Note: Where it is not possible to read the gauges of the roller brake tester while sitting in the driver’s seat, an assistant may apply the vehicle brakes during the test. The following information is for ATL approved test stations using a computer controlled RBT. follow the sequence of instructions as displayed and prompted on screen. On completion of the test print off the results. Class IV, the ATL system has a facility to automatically weigh the vehicle and the presented weight will be used for the brake efficiency calculations. Class VII, the brake efficiency must be calculated using DGW	Testing the front wheels	1.
	1. With one set of rollers revolving at a time, see information column if ATL approved gradually depress the service brake until maximum effort is achieved, or until the wheel locks and slips on the rollers.	a. Little or no braking effort is recorded from the brake on any wheel, indicating clearly that the brake is not functioning correctly
	Record the reading at which the maximum braking effort is achieved and whether “lock-up” occurs. Release the service brake.	b. see Reason for Rejection 8
	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	2. a. A significant braking effort recorded on a roadwheel, even though the brake is not applied, indicating that a brake is binding b. Evidence of severe brake grabbing or judder as the brake is applied c. The braking efforts at the roadwheels do not increase at about the same rate when the service brake is applied gradually d. The braking efforts at the roadwheels do not reduce at about the same rate when the service brake is released gradually 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 Page 28). Note: Disregard any service brake imbalance when the brake effort from each front wheel is less than 40kg.
Old pre-1906 vehicles
Vehicles certified by the London Science Museum as being designed before 1 January 1905 and constructed before 31 December 1905 do not require a parking brake	3. If the vehicle has a parking brake (handbrake), which operates on the front wheels, repeat the process outlined in 1 above using this brake and keeping the “hold-on” button or trigger in the disengaged position the whole time.	3a. Little or no braking effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly b. see Reason for Rejection 9
Vehicles of unknown test weight
conducting the brake performance checks as set out in this section the vehicle does not meet the locked wheel criteria explained in the notes under RFR 8 & 9 carry out a further brake test using a decelerometer to determine the brake efficiencies. Note: For the method of calculating Brake efficiency see section 3.8	Testing the rear wheels Release the brakes and drive the vehicle forward until the rear wheels are in the rollers. Run them together as for the front wheels to align the vehicle.
	4. With one set of rollers revolving at a time, gradually depress the service brake until maximum effort is achieved or until the wheel locks and slips on the rollers Record the maximum braking efforts and whether "lockup" occurs. Release the service brake.	4. Little or no braking effort is recorded from the brake on any wheel, indicating clearly that the brake is not functioning correctly See Reason for Rejection 8.
	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 b. Evidence of severe brake grabbing or or judder as the brake is applied c. The braking efforts at the roadwheels do not increase at about the same rate when the service brake is applied gradually
	6. Gradually release the service brake and watch how the braking effort at each wheel reduces. Stop the rollers.	6. The braking efforts at the roadwheels do not reduce at about the same rate when the service brake is released gradually
	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 method of inspection 10..	7. a. Little or no braking effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly b. see Reason for Rejection 9
	8. Record the appropriate results of the service brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3. 9. Record the appropriate results of the parking brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3.	8. The calculated service brake efficiency is too low (see Brake Efficiency Table in section 3.10 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 or 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 (2201b) is achieved by each rear wheel, or iii) for three axle vehicles; both front wheels lock and at least 50kg (1 lOlb) is achieved by each rear wheel. 9. The calculated parking brake efficiency is too low (see Brake Efficiency Table on page 30).
Testing Transmission (prop shaft) Handbrakes
	10. Carry out the following procedure Place the wheels to be tested in the rollers. Run both sets of rollers together to align the vehicle. Chock the other wheels of the vehicle fore and aft. Run both sets of rollers together. Keep the handbrake ratchet disengaged for as long as the brake is applied. Apply the brake slowly and progressively without causing transmission snatch. Record the appropriate results of the brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3.	10. The transmission brake 'parking' efficiency is too low (see Brake Efficiency Table in section 3.10) Note: To avoid possible damage, the parking brake efficiency requirement must be calculated using the appropriate vehicle weight before the brake is tested. Testing of the brake must cease as soon as the minimum efficiency requirement is reached when progressively applying the brakes.
B. Decelerometer Test
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.	1. If the vehicle is of a type which cannot be tested on a roller brake tester, . set up the decelerometer in the vehicle in accordance with the equipment manufacturer's instructions . drive the vehicle on a level road at a steady speed of approximately 20mph (32kph) and note the brake efficiency recorded when applying only
	a. the service brake	a. the service brake efficiency recorded on the decelerometer does not meet the requirements specified in the Brake Efficiency Table in section 3.10
	b. the parking brake	b. the parking brake efficiency recorded on the decelerometer does not meet the requirements specified in the Brake Efficiency Table in section 3.10
	c. while the vehicle is decelerating under the action of the service brake, note if the steering wheel tends to pull or the vehicle tends to swerve Record the appropriate results of the brake test via the VTS Device. Where the VTS Device is unserviceable see the introduction section paragraph 3.	c. when the service brake is applied there is a severe grab or judder, or there is a severe pull one way on the steering wheel, and/or the vehicle swerves appreciably
Testing transmission handbrakes
When using a decelerometer to test a transmission handbrake, keep the ratchet disengaged for as long as the brake is applied. Take the efficiency reading without the occurrence of transmission snatch or judder.
Vehicles which just pass
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.
Plate Brake Testing
The brake performance test must be carried out on a properly calibrated and maintained plate brake tester designated as acceptable for the statutory test. (Alternatively a slow-speed roller-brake tester can be used-see section 3.7 ‘A’).	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.
Vehicles which only just pass
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 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 in section 3.9, or a nominal DGW figure of 2600Kg if the presented weight is less than 2000Kg.
Testing transmission handbrakes
When using a plate tester to test a transmission handbrake, keep the ratchet disengaged for as long as the brake is applied. Take the efficiency reading without the occurrence of transmission snatch or judder.	3. Enter the appropriate data to conduct the test.
Testing the Vehicle
	1. Drive the vehicle forwards at a steady speed of about 4mph up to the plate tester. Just before the wheels are on the plate high friction surfaces, apply a light constant pressure to the brake pedal. Do not stop on the tester. Note the way in which the brake efforts fluctuate.	1. Excessive fluctuation of brake effort with a constant brake pedal effort indicating brake judder.
	2. At the same steady speed of 4mph, again drive the vehicle forwards onto the plate brake tester. As soon as the wheels are on the plate high friction braking surfaces, apply the service brake progressively until maximum effort is achieved.	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.	b. the braking efforts at both roadwheels on an axle do not increase at about the same rate when the service brake is applied
	Record the appropriate results of the brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3.	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
		d. the service brake efficiency is too low (see Brake Efficiency Table requirements in sections 3.8 & 3.10)
	3. Repeat 2 above using the parking brake.	3.
		a. Little or no effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly
		b. the parking brake efficiency is too low (see Brake Efficiency Table requirements in sections 3.8 & 3.10).
	4. Repeat 1, 2 and 3 above a second time to confirm any reason for rejection
Issue Date: 10th January 2005

The Testers Manual

3.7 Brake Performance (Roller Brake Test)

Information

Method of Inspection

Reason for rejection

A. Roller Brake Test

The brake performance test must be carried out on a properly calibrated and maintained slow-speed roller-brake tester designated as acceptable for the statutory tests, except

Vehicles for which a roller brake tester is not appropriate, or

At premises without a roller brake tester where approval has been granted for the test to be carried out by other means

If the vehicle is of a type which can be tested on a roller brake tester

Vehicles not to be tested on a roller brake tester

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 25, and C, page 26.

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

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 two pipes. Some hydraulic systems have two master cylinders.

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.

Automatic transmission

Vehicles with automatic transmission must never be roller brake tested with the gear selector in the “P” park position.

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 the driver should be allowed to drive during the test, if he/she wishes.

Note: Where it is not possible to read the gauges of the roller brake tester while sitting in the driver’s seat, an assistant may apply the vehicle brakes during the test.

The following information is for ATL approved test stations using a computer controlled RBT.

follow the sequence of instructions as displayed and prompted on screen. On completion of the test print off the results.

Class IV, the ATL system has a facility to automatically weigh the vehicle and the presented weight will be used for the brake efficiency calculations.

Class VII, the brake efficiency must be calculated using DGW

Testing the front wheels

1.

1. With one set of rollers revolving at a time, see information column if ATL approved

gradually depress the service brake until maximum effort is achieved, or until the wheel locks and slips on the rollers.

a. Little or no braking effort is recorded from the brake on any wheel, indicating clearly that the brake is not functioning correctly

Record the reading at which the maximum braking effort is achieved and whether “lock-up” occurs. Release the service brake.

b. see Reason for Rejection 8

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

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

b. Evidence of severe brake grabbing or judder as the brake is applied

c. The braking efforts at the roadwheels do not increase at about the same rate when the service brake is applied gradually

d. The braking efforts at the roadwheels do not reduce at about the same rate when the service brake is released gradually

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 Page 28). Note: Disregard any service brake imbalance when the brake effort from each front wheel is less than 40kg.

Old pre-1906 vehicles

Vehicles certified by the London Science Museum as being designed before 1 January 1905 and constructed before 31 December 1905 do not require a parking brake

3. If the vehicle has a parking brake (handbrake), which operates on the front wheels, repeat the process outlined in 1 above using this brake and keeping the “hold-on” button or trigger in the disengaged position the whole time.

3a. Little or no braking effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly b. see Reason for Rejection 9

Vehicles of unknown test weight

conducting the brake performance checks as set out in this section the vehicle does not meet the locked wheel criteria explained in the notes under RFR 8 & 9 carry out a further brake test using a decelerometer to determine the brake efficiencies.

Note: For the method of calculating Brake efficiency see section 3.8

Testing the rear wheels

Release the brakes and drive the vehicle forward until the rear wheels are in the rollers.

Run them together as for the front wheels to align the vehicle.

4. With one set of rollers revolving at a time, gradually depress the service brake until maximum effort is achieved or until the wheel locks and slips on the rollers

Record the maximum braking efforts and whether "lockup" occurs. Release the service brake.

4. Little or no braking effort is recorded from the brake on any wheel, indicating clearly that the brake is not functioning correctly See Reason for Rejection 8.

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.

6. Gradually release the service brake and watch how the braking effort at each wheel reduces. Stop the rollers.

6. The braking efforts at the roadwheels do not reduce at about the same rate when the service brake is released gradually

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 method of inspection 10..

7.

a. Little or no braking effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly

b. see Reason for Rejection 9

8. Record the appropriate results of the service brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3.

9. Record the appropriate results of the parking brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3.

9. The calculated parking brake efficiency is too low (see Brake Efficiency Table on page 30).

1. With one set of rollers revolving at a time,
see information column if ATL approved

2.
a. A significant braking effort recorded on a roadwheel, even though the brake is not applied, indicating that a brake is binding

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 Page 28).
Note: Disregard any service brake imbalance when the brake effort from each front wheel is less than 40kg.

3a. Little or no braking effort is recorded from the parking brake on any wheel, indicating clearly that the brake is not functioning correctly

b. see Reason for Rejection 9

4. Little or no braking effort is recorded from the brake on any wheel, indicating clearly that the brake is not
functioning correctly

See Reason for Rejection 8.

9.
Record the appropriate results of the parking brake test via the VTS Device, which will calculate the results. Where the VTS Device is unserviceable see the introduction section paragraph 3.