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Oct 07, 2023

MOT inspection manual: cars and passenger vehicles

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

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.

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.

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:

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

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

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:

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:

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.

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

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:

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.

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

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:

Make sure the engine is switched off.

Deplete the stored vacuum by repeatedly applying the service brake.

Fully apply the brake and hold at a constant pressure.

Start the engine.

Note if the pedal can be felt to travel further.

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.

Repairs to the pressure lines of hydraulic brake systems are unacceptable unless suitable connectors are used. Compression joints of a type using separate ferrules are not suitable.

Unacceptable repairs to brake lines should be failed using RfR 1.1.21 (d)

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

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.

An illuminated brake wear indicator is not a reason for failure.

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.

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.

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.

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

The primary brake tester must be used unless the vehicle is unsuitable due to its drive configuration, transmission type or braking system. If this is the case, a full or partial decelerometer test may be appropriate. You should consider 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.

When testing using an Automated RBT or a plate brake tester, the vehicle test weight for Classes 3 and 4 is the weight shown by the brake test equipment.

For non-automated roller brake testers the brake test weight must be obtained from a brake data chart or 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 and adding the ULW, for example: 52 seats × 63.5kg = 3302kg + 5,250kg ULW = 8552kg.

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.

Additional braking devices, such as electronic retarders, should not be operated during the brake test.

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.

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.

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.

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

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.

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.

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

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.

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.

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.

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:

To use a plate brake tester:

Enter the appropriate data to conduct the test.

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

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.

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.

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.

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.

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

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.

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:

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.

“Not tested” or “Unable to be tested” must only be used where it becomes apparent during the test that the particular item cannot be tested, and this could not have been identified prior to starting the test. The reason for selecting the failure must be included in the additional information box.

Vehicles first used before 1 August 1980 may not have a manufacturer’s plate.

Most manufacturer’s plates will usually show four weights:

Three-axle vehicles will show an additional maximum axle weight.

Some vehicles will not show a train weight because they have not been designed to tow a trailer.

Goods vehicles may show two columns of weights.

In these cases, one column will be the maximum design weights and the other column will be the maximum permissible weights in Great Britain, otherwise known as Maximum Authorised Mass (MAM).

Where a Design Gross Weight is not shown, then the Gross GB Weight or MAM is used for brake percentage efficiency calculations on vehicles in Class 7.

Note: On goods vehicles presented with a ‘Ministry’ plate (VTG6 or VTG6T) then the information displayed on that plate will always override the information displayed on the Manufacturer’s plate.

The registration number and chassis number on the ‘Ministry’ plate must always be cross checked to ensure the plate relates to that vehicle.”

An example of a manufacturer’s plate can be found in Section 2 of the Introduction.

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:

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

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.

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

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

Roller and plate brake tests:

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

Enter other defects manually.

Plate brake tests:

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

Enter other defects manually.

Decelerometer tests:

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

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.

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.

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.

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

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.

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

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.

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.

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.

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

Note the recorded brake efficiency.

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

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.

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

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

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.

The primary brake tester must be used unless the vehicle is unsuitable due to its drive configuration, transmission type or braking system. If this is the case, a decelerometer or gradient test may be appropriate. A gradient test must only be carried out if the parking brake cannot be tested using the primary brake tester or decelerometer. This will usually only be necessary on certain all-wheel drive vehicles with electronic parking brakes where no vehicle technical information is available.

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.

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.

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

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.

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

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

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

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.

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.

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.

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

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.

A gradient test must only be carried out on vehicles that are not suitable for a parking brake test with the primary brake tester or decelerometer. This will usually only be necessary on certain all-wheel drive vehicles with electronic parking brakes where no vehicle technical information is available.

A suitable gradient is considered to be one which:

Reverse the vehicle onto the gradient.

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

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

For details of entering brake test results see Section 1.2.2.

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%.

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.

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.

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. Not all vehicles first used on or after 1 January 2010 will have ABS, so the failure only applies where the system has obviously been removed.

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

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.