MOT inspection manual: cars and passenger vehicles

1. Brakes

Brake condition and operation, service brakes, secondary brakes, parking brakes, anti-lock braking system (ABS), electronic braking system (EBS) and brake fluid rules and inspection for car and passenger vehicle MOT tests.

1.1. Condition and operation

In this section


1.1.1. Service brake pedal or hand lever pivot

Defect Category
(a) Pivot too tight Major
(b) Excessive wear or free play Major

1.1.2. Service brake pedal or hand lever condition and travel

A brake pedal rubber is an anti-slip material and is therefore not regarded as a defect if it’s worn smooth.

A brake pedal without a rubber usually has grooves or raised sections to provide grip in wet conditions and should be rejected if it’s worn smooth. However, some vehicles may have been manufactured with a brake pedal which did not incorporate grooves or the fitting of an anti-slip material and these should not be rejected.

You should reject a brake pedal if its grooves or raised grip sections are worn smooth. However, you should not reject a brake pedal if the vehicle has been manufactured with one that does not have grooves or anti-slip material.

Often a vehicle is fitted with an aftermarket brake pedal rubber. It is not a defect if the design pattern of the brake pedal rubber is worn smooth.

A vehicle should only be failed for insufficient reserve if the pedal or lever is touching the floor/handlebar. Checks on vehicles with power-assisted braking systems should be carried out with the engine off.

It may be possible on motorcycle derived systems for the brake lever to touch the handlebar. In such cases the extent of reserve travel should be assessed during the brake test.

Defect Category
(a) Insufficient reserve travel Major
(b) Service brake control:

(i) not releasing correctly
(ii) functionality of brakes affected


Minor
Major
(c) Anti-slip provision missing, loose or worn smooth Major

1.1.3. Air and vacuum systems

Vehicles first used before 1 October 1937 do not need to be tested for air and vacuum systems.

A vehicle with an ULW up to and including 3,050kg, with a reservoir coupled direct to the induction manifold or a reservoir integral in a servo unit, does not need to be fitted with a warning device.

To check the build-up of air or vacuum:

  1. Completely empty the reservoir by repeatedly pressing the service brake pedal.

  2. Start the engine and run it at just below the governed speed if diesel, or at 2,000rpm if petrol.

  3. Check the time it takes for the warning device to stop operating. Pressure build-up is considered satisfactory if the warning device stops operating within:

  • 3 minutes for pressure systems
  • 1 minute for vacuum systems

For checks that require reference to a pressure or vacuum gauge warning mark, but no warning mark is present, the following reference values should be used:

  • 45psi (3.1kg/cm2 or 3 bar) for a pressure gauge
  • 10” to 12” (25 to 30cm) for a vacuum gauge
Defect Category
(a) Insufficient pressure/vacuum assistance for less than:

(i) four brake applications after the warning device has operated (or gauge shows an unsafe reading)
(ii) two brake applications after warning device has operated (or gauge shows an unsafe reading)


Major

Dangerous
(b) Time taken to build up air pressure/vacuum to safe working value not in accordance with the requirements Major
(c) Repeated operation of any ancillary air or vacuum system completely depletes the stored air or vacuum for the braking system Major
(d) Air leak causing a noticeable drop in pressure or audible air leak Major
(e) External damage likely to affect the function of the braking system Major

1.1.4. Low-pressure warning

Vehicles first used before 1 October 1937 do not need to be tested for low-pressure warning.

A vehicle with an ULW up to and including 3,050kg with a reservoir coupled direct to the induction manifold or a reservoir integral in a servo unit, is not necessarily required to be fitted with a warning device.

Warning devices may be visual or audible but only one needs to work if both are fitted.

Some vehicles with full power hydraulic braking systems will illuminate the low-pressure warning light as soon as the ignition is switched on. It is not a defect unless the warning light stays on after the engine has been started.

Defect Category
(a) Low-pressure warning gauge or indicator:

(i) malfunctioning or defective
(ii) not identifying low-pressure


Minor
Major

1.1.5. Hand operated brake control valve

All vehicles with a secondary brake control - in addition to or in place of the normal parking brake lever - must be inspected.

Defect Category
(a) Control cracked, damaged or excessively worn Major
(b) Control insecure on valve or valve insecure Major
(c) Loose connections or leaks in the system Major
(d) Malfunctioning Major

1.1.6. Parking brake lever or control

Vehicles first used before 1906 do not need to have a parking brake.

Some defects in this sub-section may not apply to the type of parking brake fitted.

A parking brake lever must have obvious excessive travel before being rejected.

An electronic parking brake (EPB) may apply automatically in certain conditions, such as when the ignition is switched off or when the driver’s door is opened. Testers should be aware of this throughout the test.

Electronic parking brakes must be maintained in operation by direct mechanical means, even though they are applied electronically. However, the mechanism for keeping the brakes applied is usually within brake calliper or motor gear assembly and therefore not easy to see.

Hydraulic parking brakes as an only means of operation are not acceptable on vehicles first used on or after 1 January 1968. However, they may be used to assist the application or release of a mechanical brake.

Quadricycles may be fitted with one of the following types of parking brake:

  • an over-centre lever that is mounted on handlebars
  • a gear lever that operates a cable when it’s moved into the park position
  • a transmission lock, which is the ‘P’ position on machines with continuously variable transmission (CVT)

These machines are type approved and should not be rejected for design features that prevent them from meeting the stated requirements.

If the parking brake is the ‘P’ position on the gearbox, the efficiency of the brake cannot be tested. The tester must therefore assess the brake by using a gradient (ideally 16%), or by attempting to push the machine when ‘P’ is selected.

The over-centre lever type can be brake tested as normal using one of the approved test methods.

Defect Category
(a) Ratchet not holding correctly Major
(b) Parking brake lever pivot or ratchet mechanism:

(i) obviously worn
(ii) worn to the extent that the brake may inadvertently release


Minor
Major
(c) Parking brake lever has excessive movement indicating incorrect adjustment Major
(d) Parking brake control missing, defective or inoperative Major
(e) Electronic parking brake MIL indicates a malfunction Major
(f) Parking brake is not capable of being maintained in operation by direct mechanical action only (vehicle first used on or after 1 January 1968) Major

1.1.7. Brake valves

Defect Category
(a) Valve:

(i) damaged or excessive air leak
(ii) leaking such that brake functionality is affected


Major
Dangerous
(b) Excessive oil discharge from a compressor or brake valve Minor
(c) Valve insecure or inadequately mounted Major
(d) Hydraulic fluid:

(i) leak from a brake valve
(ii) leak from a brake valve such that brake functionality is affected


Major
Dangerous

1.1.8. Not in use

1.1.9. Pressure storage reservoirs

Vehicles first used on 1 October 1937 or later must have their air and air/hydraulic braking systems inspected.

Defect Category
(a) Reservoir:

(i) has minor damage or corrosion
(ii) heavily damaged, heavily corroded or leaking


Minor
Major
(b) Drain device on an air brake system:

(i) operation affected
(ii) inoperative


Minor
Major
(c) Reservoir insecure or inadequately mounted Major

1.1.10. Brake servo units and master cylinder (hydraulic systems)

Hydraulic brake fluid level checks are confined to transparent reservoirs or where an indicator is fitted. Reservoir caps should not be removed.

A brake fluid warning lamp may be shared with other components, for example to indicate that brake pads are worn or the parking brake is applied. Class 3 vehicles are not inspected for brake fluid warning lamp.

To check the brake vacuum servo:

  1. Make sure the engine is switched off.

  2. Deplete the stored vacuum by repeatedly applying the service brake.

  3. Fully apply the brake and hold at a constant pressure.

  4. Start the engine.

  5. Note if the pedal can be felt to travel further.

Defect Category
(a) Brake servo:

(i) defective or ineffective
(ii) inoperative


Major
Dangerous
(b) Master cylinder:

(i) defective but brake still operating
(ii) leaking


Major
Dangerous
(c) Master cylinder insecure Major
(d) Brake fluid:

(i) below minimum mark
(ii) significantly below minimum mark
(iii) not visible


Minor
Major
Dangerous
(e) Master cylinder reservoir cap missing Major
(f) Brake fluid warning light illuminated or defective Minor
(g) Incorrect functioning of brake fluid level warning device Minor

1.1.11. Rigid brake pipes

If the metal brake pipes have surface dirt that needs to be removed before it’s possible to assess their condition, you can lightly scrape the pipe with a specialist brake pipe corrosion tool or the corrosion assessment tool ‘spade end’. It must be done with care so that any protective coating does not get damaged.

Chafing, corrosion or damage to a rigid brake pipe so that its wall thickness is reduced by 1/3 (approximately 0.25mm for typical hydraulic brake pipe) justifies rejection, although it’s accepted that this is not easy to determine. If you are not sure whether the pipe is sufficiently deteriorated to justify rejection, you should give the benefit of the doubt.

Defect Category
(a) Brake pipe is at imminent risk of failure or fracture Dangerous
(b) Leaking brake pipe or connection:

(i) on an air brake system
(ii) on a hydraulic system


Major
Dangerous
(c) Brake pipe damaged or excessively corroded Major
(d) Brake pipe:

(i) inadequately clipped or supported
(ii) likely to become detached or damaged


Minor
Major

1.1.12. Flexible brake hoses

You should reject a hose for being excessively damaged or chafed only if it’s severe enough to expose the reinforcement.

Defect Category
(a) Brake hose damaged and likely to fail Dangerous
(b) Flexible brake hose:

(i) slightly damaged, chafed or twisted
(ii) excessively damaged, deteriorated, chafed, twisted or stretched


Minor
Major
(c) Brake hoses or connections leaking on:

(i) air brake systems
(ii) hydraulic systems


Major
Dangerous
(d) Brake hose bulging under pressure Major
(e) Brake hose porous Major
(f) Brake hose ferrules:

(i) excessively corroded
(ii) excessively corroded and likely to fail


Major
Dangerous

1.1.13. Brake linings and pads

Some brake pads have metal wear indicators so that when the pads become excessively worn the metal indicator touches the disc making a squealing sound. Other pads may have a cut, which if worn away indicates that the pad must be replaced.

Defect Category
(a) Brake lining or pad:

(i) worn down to wear indicator
(ii) worn below 1.5mm


Major
Dangerous
(b) Brake lining or pad contaminated with oil, grease etc. Major
(c) Brake lining or pad missing or incorrectly mounted Dangerous

1.1.14. Brake discs and drums

A brake disc or drum must be significantly worn before you should reject it. Being worn below the manufacturer’s recommended limits is not a reason in itself.

Defect Category
(a) Brake disc or drum:

(i) significantly and obviously worn
(ii) insecure, fractured or otherwise likely to fail


Major
Dangerous
(b) Contaminated with oil, grease etc. Major
(c) Missing Dangerous
(d) Brake drum back plate insecure Major

1.1.15. Brake cables, rods, levers and linkages

Defect Category
(a) Cable damaged or knotted Major
(b) Component excessively worn or corroded Major
(c) Cable, rod or joint insecure Major
(d) Cable guide defective affecting operation Major
(e) Restriction in free movement of the braking system Major
(f) Abnormal movement of levers indicating maladjustment or excessive wear Major

1.1.16. Brake actuators - including spring brakes, hydraulic cylinders and callipers

Defect Category
(a) Actuator cracked or damaged and:

(i) braking performance not affected
(ii) braking performance affected


Major
Dangerous
(b) Actuator leaking and:

(i) braking performance not affected
(ii) braking performance affected


Major
Dangerous
(c) Actuator insecure or inadequately mounted and:

(i) braking performance not affected
(ii) braking performance affected


Major
Dangerous
(d) Actuator:

(i) excessively corroded
(ii) excessively corroded and likely to crack


Major
Dangerous
(e) Actuator has:

(i) excessive travel of operating system indicating need for adjustment
(ii) no reserve travel and braking performance affected


Major
Dangerous

1.1.17. Load sensing valve

Defect Category
(a) Load sensing valve linkage defective Major
(b) Load sensing valve linkage obviously incorrectly adjusted Major
(c) Load sensing valve seized or inoperative and:

(i) ABS functioning
(ii) ABS not fitted or inoperative


Major
Dangerous
(d) Load sensing valve missing where fitted as standard Dangerous

1.1.18. Brake slack adjuster

Defect Category
(a) Adjuster damaged, seized or having abnormal movement, excessive wear or incorrect adjustment Major
(b) Adjuster defective Major
(c) Incorrectly installed Major

1.1.19. Additional braking device (retarder), if fitted

An endurance braking system, such as an exhaust brake or electronic retarder is only likely to be fitted to some large motor caravans and category M2 and M3 vehicles.

Defect Category
(a) Endurance braking system connectors or mountings:

(i) insecure
(ii) insecure and functionality affected


Minor
Major
(b) Endurance braking system obviously defective Major

1.1.20. Not in use

1.1.21. Complete braking system

You must check the strength and continuity of the vehicle’s load bearing members and their supporting structure or panelling around any braking component mounting.

Guidance for assessing corrosion and use of the corrosion assessment tool can be found in Appendix A.

Defect Category
(a) Other braking system (e.g. antifreeze pump, air dryer etc.) component damaged or corroded:

(i) to the extent that the braking system is adversely affected
(ii) leaking and system functionality adversely affected



Major
Dangerous
(b) Air or antifreeze:

(i) leaking
(ii) to the extent that braking performance is affected


Minor
Major
(c) Any component insecure or inadequately mounted Major
(d) Braking system component modification:

(i) unsafe
(ii) adversely affecting braking performance


Major
Dangerous
(e) The strength or continuity of the load bearing structure within 30cm of any braking system actuation component mounting (a prescribed area):

(i) is significantly reduced (see Appendix A)
(ii) is so weakened that the functionality of the braking system is affected



Major
Dangerous

1.2. Service brake performance and efficiency

In this section


1.2.1. Performance

You must ensure that the vehicle is in a safe condition for the test to be carried out.

If the primary brake tester is not suitable for the vehicle’s drive configuration, transmission type or braking system, a full or partial decelerometer test may be appropriate. You should take into account any additional information from the vehicle manufacturer.

When conducting a test on a roller brake tester (RBT) where more than half of the wheels of a brake system lock the efficiency requirements for that system are considered to be met.

Alternatively, the efficiency requirements are met if the front wheels lock on the service brake of an unladen Class 7 vehicle with at least a 100kg force at each rear wheel for a two-axle vehicle, or at least 50kg force at each rear wheel on a three-axle vehicle.

Vehicles of unknown test weight can be tested on either an RBT or plate brake tester (PBT). However, if the number of wheel locks are not achieved for any system on a non-ATL RBT, a decelerometer test must be used to establish the overall brake efficiency of the relevant system(s).

Certain converted passenger vehicles, such as motor caravans and ambulances, may have a kerb weight greatly in excess of the base model weight displayed by the MOT testing service. In these circumstances, the vehicle should be treated as having an unknown test weight.

Some tricycles with two brake controls may have a linked braking system. The brake force used in the efficiency calculation is the total from all wheels when operated by that control only. Additional braking devices, such as electronic retarders, should not be operated during the brake test.

Using a roller brake tester

Ensure that the vehicle, or system, under test is suitable for testing using a roller brake tester. If the vehicle or system is unsuitable, it should be tested with a decelerometer.

ATL test procedure

Automated test lane (ATL) approved test stations should position the front wheels of the vehicle in the rollers of the brake tester and follow the sequence of instructions as displayed and prompted on screen. If a vehicle is ejected from the brake rollers, the required brake efforts may not be achieved. In such cases the test should be repeated in manual mode, running each roller individually.

Non - ATL test procedure

You are permitted to use an alternative procedure to that specified below as long as all the testable elements are adequately covered.

  1. Position the wheels of the first axle to be tested in the brake rollers and then run both sets of rollers together in a forward direction until the vehicle is aligned. With the rollers still running, note whether a significant brake effort is recorded from any wheel without a brake being applied.

  2. Gradually apply the service brake and watch how the braking effort for each wheel increases. Stopping short of lock up or maximum effort, hold a steady pedal pressure and check there is no excessive brake effort fluctuation with each revolution of the road wheel.

  3. Gradually release the service brake and observe how the braking effort at each wheel reduces.

  4. Gradually depress the service brake again, this time until maximum effort is achieved, or until the wheel locks and slips on the rollers. Stop the rollers.

  5. Record the reading at which the maximum braking effort is achieved and whether brake “lock-up” occurs. Stop the rollers if they have not stopped automatically.

  6. Place the wheels of the next axle in the brake rollers and repeat the above procedure.

When checking maximum effort, testers can elect to run the brake rollers individually or together, depending on the suitability of the RBT. However, if the rollers are run together and the vehicle fails to meet the minimum performance requirement, the test must be repeated running the rollers individually.

If both rollers are run together, it will almost certainly be necessary to chock the wheels that are not being tested.

Using a plate brake tester

For vehicles other than Class 7, establish the actual presented weight of the vehicle.

For Class 7 vehicles, the brake efficiency will be calculated using one of the following:

  • the actual design gross weight (DGW) where the presented weight is at least 2,000kg (the DGW is obtained from the manufacturer’s plate fitted to the vehicle)
  • a nominal DGW figure of 2,600kg if the presented weight is less than 2,000kg

To use a plate brake tester:

  1. Enter the appropriate data to conduct the test.

  2. For each check, drive the vehicle forwards at a steady speed of about 4mph up to the plate tester.

  3. On the first run, 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. Take note of the way the brake efforts fluctuate.

  4. On the second run, as soon as the wheels are on the plate high friction braking surfaces, apply the service brake progressively until maximum effort is achieved.

  5. Take note of the way the brake efforts increase and the maximum values achieved.

If a vehicle fails any aspect of the plate brake test, the check should be repeated to confirm the result.

Using a decelerometer

If the vehicle or system cannot be tested on a roller brake tester, set up the decelerometer in the vehicle in accordance with the equipment manufacturer’s instructions.

  1. Drive the vehicle on a level road at a steady speed of approximately 20mph (32kph) and progressively apply the service brake to maximum.

  2. Note whether the vehicle or steering pulls severely one way and the brake efficiency recorded.

Before carrying out a decelerometer test on the public highway, testers must ensure they are suitably qualified to drive the vehicle and are familiar with the controls. If a vehicle has special controls, such as in disability vehicles, the vehicle presenter should be allowed to drive during the test if he/she wishes.

Calculating brake imbalance

For the majority of vehicles, the MOT testing service will calculate brake imbalance automatically. However, when this is not the case, such as for tricycles and quadricycles or if MTS is not working, you must calculate the brake imbalance against the maximum brake efforts on each axle in the following way:

Brake imbalance equation: (higher brake effort - lower brake effort / higher brake effort) x 100 = % imbalance

Disregard any brake imbalance across an axle if the lower recorded effort is as a result of a locked wheel or if the higher brake effort from a wheel is not more than 40kg.

The check for rear axle brake imbalance does not apply to tricycles or quadricycles.

Defect Category
(a) Braking effort:

(i) inadequate at a wheel
(ii) not recording at a wheel


Major
Dangerous
(b) Brakes imbalance across an axle such that:

(i) the braking effort from any wheel is less than 70% of the maximum effort recorded from the other wheel on the same axle. Or in the case of testing on the road, the vehicle deviates excessively from a straight line
(ii) the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle


Major


Dangerous
(c) A brake on any wheel grabbing severely Major
(d) Abnormal lag in brake operation on a wheel Major
(e) Excessive fluctuation in brake effort through each wheel revolution Major
(f) Significant brake effort recorded with no brake applied indicating a binding brake Major
(g) Brake performance unable to be tested Major

1.2.2. Efficiency

Calculating brake efficiency

For most vehicles the MOT testing service will calculate brake efficiencies automatically.

If MTS is not working, add the brake efforts from each wheel for the system that is being tested and carry out the following calculation:

Brake efficiency equation: (% efficiency = total brake effort / vehicle test weight x 100

The vehicle test weight will depend on the vehicle test class.

For Classes 3 and 4 use the weight shown by the brake test equipment. Otherwise, take the weight from a weight data chart or some other reliable source.

For Class 7 use the DGW from the manufacture’s plate or, the nominal DGW of 2,600kg if using a plate brake tester and the presented weight is less than 2,000kg.

For Class 5 use the lesser of the DGW or maximum authorised mass (MAM) from the manufacturer’s plate. On vehicles where only the ULW is displayed, you must calculate the DGW by multiplying the number of passenger seats by 63.5kg (or 140lbs) and adding the ULW, for example: 52 seats × 63.5kg = 3302kg + 5,250kg ULW = 8552kg

Efficiency requirements

For vehicle category definitions see the ‘Abbreviations and definitions’ in the ‘Introduction’.

Vehicle type Efficiency requirement
M1 vehicles having a service brake operating on at least 4 wheels and which were first used:
- on or after 1 September 2010
- before 1 September 2010


58%
50%
N1 vehicles 50%
M2 and M3 vehicles having a service brake operating on at least 4 wheels which were first used:
- on or after 1 January 1968
- before 1 January 1968


50%
45%
L2 and L6 vehicles with a single service brake control that operates the brakes on all wheels 40%
L5 vehicles with a single service brake control that operates the brakes on all wheels which were first used:
- on or after 1 January 1968
- before 1 January 1968


50%
40%
Vehicles first used before 1 January 1968 which do NOT have one means of control operating on at least 4 wheels and which have one brake system with two means of control or two brake systems with separate means of control
30% from 1st means of control
25% from 2nd means of control
Any L category vehicle with two service brake systems each having a separate means of operation
30% from 1st means of control
25% from 2nd means of control
Vehicles first used before 1 January 1915 only require one efficient braking system No specific requirement

Brake test results

Brake efforts achieved during a test should be entered on the MOT testing service as follows:

Roller and plate brake tests:

  1. Enter the brake effort from each wheel and whether they ‘lock-up’. The MOT testing service will automatically calculate the brake efficiency and out of balance results

  2. Enter other defects manually.

Plate brake tests:

  1. Enter the brake effort from each wheel. The MOT testing service will automatically calculate brake efficiency and out of balance results.

  2. Enter other defects manually.

Decelerometer tests:

  1. Enter the efficiencies recorded by the meter. The MOT testing service will automatically pass or fail the vehicle on brake efficiency.

  2. Enter other defects manually.

If the MOT testing service is unavailable, refer to the latest edition of the MOT Testing Guide.

In cases where the required brake efficiency is only just met, but the tester knows that a higher performance figure is normally obtained for the vehicle type, the vehicle presenter should be informed.

Defect Category
(a) Service brake efficiency:

(i) below minimum requirement
(ii) less than 50% of the required value


Major
Dangerous

1.3. Secondary brake performance and efficiency

In this section


1.3.1. Performance

This inspection is only for vehicles with a single line braking system. If the secondary brake is also the park brake then there is no need to carry out a separate park brake test.

The secondary brake control may be the parking brake lever, or a separate brake control.

When testing transmission parking brakes, the minimum secondary brake efficiency requirement must be calculated before the brake is tested. As soon as the minimum efficiency requirement is reached the brake testing must cease to avoid any possible damage.

Using a roller brake tester

  1. On each axle which has a secondary brake fitted, run the rollers and gradually apply the secondary brake keeping any “hold-on” button or trigger disengaged the whole time, watching how the braking effort for each wheel increases.

  2. Continue to apply the parking brake until maximum effort is achieved, or until the wheels lock and slip on the rollers.

  3. Record the reading at which the maximum braking effort is achieved and whether the wheels locked. Stop the rollers if they have not stopped automatically.


Using a plate brake tester

  1. Drive the vehicle forwards at a steady speed of about 4mph up to the plate tester.

  2. As soon as the wheels are on the plate high friction braking surfaces, gradually apply the secondary brake, keeping any ‘hold-on’ button or trigger disengaged the whole time, until maximum effort is achieved.

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

If a vehicle fails any aspect of the plate brake test, the check should be repeated to confirm the result.

Using a decelerometer

If the vehicle or system 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.

  1. Drive the vehicle on a level road at a steady speed of approximately 20mph (32kph) and progressively apply the secondary brake to maximum.

  2. Note the recorded brake efficiency.

Brake test results

For details of entering brake test results, see Section 1.2.2.

Defect Category
(a) Braking effort:

(i) inadequate at any wheel
(ii) not recording at any wheel


Major
Dangerous
(b) Brakes imbalance across an axle such that:

(i) the braking effort from any wheel is less than 70% of the maximum effort recorded from the other wheel on the same axle. Or in the case of testing on the road, the vehicle deviates excessively from a straight line.
(ii) the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle


Major


Dangerous
(c) A brake on any wheel grabbing severely Major

1.3.2. Efficiency

Vehicles with a single line braking system must meet the following minimum secondary brake efficiency requirements:

Vehicle type Efficiency requirement
M2 and M3 vehicles having a service brake operating on at least 4 wheels which were first used before 1 January 1968 20%
Vehicles first used before 1 January 1968 which do NOT have one means of control operating on at least 4 wheels and which have one brake system with two means of control or two brake systems with separate means of control 25% from 2nd means of control
All other vehicles 25%

Vehicles first used before 1 January 1915 must only have one efficient braking system.

Defect Category
(a) Parking brake efficiency:

(i) below minimum requirement
(ii) less than 50% of the required value


Major
Dangerous

1.4. Parking brake performance and efficiency

In this section


1.4.1. Performance

You only need to inspect vehicles that have not already had the parking brake system tested as the secondary brake.

These vehicles must instead meet the secondary brake test requirements. For details see Section 1.3.1 and 1.3.2.

When testing transmission parking brakes, the minimum parking brake efficiency requirement must be calculated before the brake is tested. As soon as the minimum efficiency requirement is reached the brake testing must cease to avoid any possible damage.

A small number of large vehicles, such as some American motor caravans, have a parking brake which is not suitable for a dynamic brake test. In such cases a gradient test must be carried out.

Three-wheeled vehicles only require a parking brake on one wheel.

Using a roller brake tester

  1. Run the rollers on each axle that has the parking brake fitted and gradually apply the parking brake, keeping any ‘hold-on’ button or trigger disengaged the whole time.

  2. Continue to apply the brake until maximum effort is achieved, or until the wheels lock and slip on the rollers.

  3. Record the reading at which the maximum braking effort is achieved and whether the wheels locked. Stop the rollers if they have not stopped automatically.

Large vehicles fitted with spring brakes, lock actuators or air assisted parking brakes may require an applied brake test for assessing parking brake efficiency. This test must only be conducted on an approved Class 5 roller brake tester with the appropriate ‘Applied Brake Test’ programme.

  1. Apply the parking brake fully and then release any power assistance. The service brake may be used to assist in setting the parking brake.

  2. Start each brake roller in turn and note the recorded maximum effort.

Using a plate brake tester

  1. Drive the vehicle forwards at a steady speed of about 4mph up to the plate tester.

  2. As soon as the wheels are on the plate’s high friction braking surfaces, gradually apply the parking brake, keeping any “hold-on” button or trigger disengaged the whole time, until maximum effort is achieved.

  3. Note the maximum values achieved.

If a vehicle fails any aspect of the plate brake test, the check should be repeated to confirm the result.

Using a decelerometer

If the vehicle or system cannot be tested on a roller brake tester, set up the decelerometer in the vehicle as instructed by the equipment manufacturer.

  1. Drive the vehicle on a level road at a steady speed of approximately 20mph (32kph) and progressively apply the parking brake to maximum.

  2. Note the recorded brake efficiency.

Decelerometer brake testing must always be carried out on suitable roads with as little traffic as possible. A particular public road should not be used for tests so frequently that it could cause complaints from residents.

Using a gradient tester

A gradient tester can be used on vehicles that are not suitable for a parking brake test with the primary brake tester or decelerometer.

  1. Reverse the vehicle onto the 16% gradient.

  2. Hold the vehicle on the service brake whilst setting the parking brake.

  3. Release the service brake and note if the vehicle is held on the gradient.

Brake test results

For details of entering brake test results see Section 1.2.2.

Defect Category
(a) Parking brake inoperative on one side, or in the case of testing on the road, the vehicle deviates excessively from a straight line Major

1.4.2. Efficiency

You only need to inspect vehicles that have not already had the parking brake system tested as the secondary brake.

These vehicles must instead meet the secondary brake test requirements. For details see Section 1.3.1 and 1.3.2.

For details of conducting the test see Section 1.4.1.

M2 and M3 vehicles that were first used before 1 January 1968 and that have a service brake operating on at least 4 wheels, have no specified parking brake efficiency requirement. However, they must have a parking brake that can prevent at least two wheels from turning. For vehicle category definitions see ‘Abbreviations and definitions’ in the ‘Introduction’.

Vehicles first used before 1 January 1915 only need one efficient braking system. They do not need to meet a specified efficiency requirement.

All other vehicles must achieve a minimum parking brake efficiency of 16%.

Defect Category
(a) Parking brake efficiency:

(i) below minimum requirement
(ii) less than 50% of the required value


Major
Dangerous

1.5. Additional braking device (retarder) performance

You must inspect any additional braking device fitted, such as an electric or fluid retarder or an exhaust brake. It is not necessary to drive the vehicle to carry out this inspection.

Defect Category
(a) Control for electronic retarder does not allow gradual variation in effort Major
(b) System obviously inoperative Major

1.6. Anti-lock braking system (ABS)

You must inspect any ABS systems fitted.

When testing ABS equipped vehicles, the road wheels that are lifted off the ground should not be allowed to rotate when the ignition is on. This can cause the ABS system to indicate a fault which may require specialist equipment to rectify.

If the ABS has been intentionally rendered inoperative, the whole system must be removed. This does not apply to sensor rings or other ABS components which are an integral part of another component, such as a brake disc or drive shaft.

It’s not permissible to remove or disable the ABS from a vehicle first used on or after 1 January 2010.

Defect Category
(a) Warning device not working Major
(b) Warning device shows system malfunction Major
(c) Wheel speed sensors missing or damaged Major
(d) Wiring damaged Major
(e) Other components missing or damaged Major

1.7. Electronic braking system (EBS)

You must inspect the warning lamp operation on vehicles with an electronically controlled air braking system.

Defect Category
(a) Warning device not working Major
(b) Warning device shows system malfunction Major

1.8. Brake fluid

Hydraulic brake fluid level checks are confined to transparent reservoirs, reservoir caps should not be removed. On many vehicles, you will not be able to see if the brake fluid is contaminated. You should only fail a vehicle if you can clearly see that the fluid is contaminated.

Defect Category
(a) Brake fluid contaminated Major