GB/T 24926-2024Performance and measurement method for braking of all-terrain vehicles (English PDF)

3 Terms and definitions

3.1 control - part operated directly by the driver in order to supply the transmission device with the energy required for braking or for controlling the brake.

3.2 transmission - combination of components between the control and the brake that links their functions.

3.3 service brake system - braking system that decelerates a vehicle in motion.

3.4 combined brake system, CBS - service brake system in which the brakes on all the wheels are actuated by a single control.

3.5 secondary brake system - second service brake system fitted to a vehicle equipped with a combined brake system.

3.6 split service brake system, SSBS - braking system that controls the brakes on all the wheels. Note: the system is actuated by a single control and is made up of two or more sub-systems; failure of any one sub-system, for instance a failure caused by leakage of a hydraulic line, does not affect the function of the other sub-systems.

3.7 engine disconnected - the engine is disconnected from the driven wheels.

3.8 initial brake temperature - temperature of the brake before any braking is applied. Note: where several brakes are actuated together, the temperature of the hottest brake is taken.

3.9 test speed - speed of the vehicle at the moment the driver begins to operate the control. Note: where the test requires two controls to be operated at the same time, the moment at which the first control begins to be operated is taken.

3.10 wheel lock - condition in which the slip ratio of the wheel is 1.00.

3.11 average control force - average value of the control force while the vehicle speed falls from 80 % to 10 % of the test speed.

3.12 laden - the vehicle carries the maximum payload mass declared by the manufacturer.

3.13 lightly loaded - the lesser of the laden mass and the sum of the kerb mass of the complete vehicle, the driver mass (75 kg) and the mass of the test equipment (15 kg).

3.14 brake system - combination of parts that progressively decelerates or stops a moving vehicle, or holds a stationary vehicle at rest. Note: the system consists of the control, the transmission and the brake, but does not include the engine.

3.15 brake - part of the brake system that produces the force opposing the motion of the vehicle.

3.16 power-assisted braking system - braking system in which one or more energy sources assist the muscular effort of the driver in applying the braking force. Note: a vacuum-assisted braking system with a vacuum booster is an example.

3.17 maximum velocity, V max - highest speed the vehicle can reach in the lightly loaded condition.

4 Structural and functional requirements

4.1.1 The all-terrain vehicle is required to be fitted with braking systems for deceleration, stopping and parking that meet the performance requirements.

4.1.2 The brake friction linings are not to contain asbestos.

4.1.3 With proper lubrication and adjustment, operation of the braking system is to be smooth and free.

4.1.4 The thickness of the friction lining is to be visible without dismantling the brake; where it is not visible, the wear is to be assessable through a device designed for that purpose.

4.1.5 Wear of the friction lining is to be compensated by manual or automatic adjustment, and the brake is to be adjustable to an effective working position before the lining reaches the point at which it needs replacement.

4.1.6 After correct adjustment, the parts of the braking system are not to touch unrelated parts while working.

4.1.7 In a split service brake system, leakage of one hydraulic sub-system is not to affect the braking capability of the other sub-systems.

4.1.8 Each brake circuit of a hydraulic braking system is to have a reservoir whose minimum capacity is 1.5 times the volume of fluid needed to take up the adjustment of all the friction linings of that circuit from their new position to their wear limit.

4.1.9 The reservoir of a hydraulic braking system is to be designed and made so that its fluid level can be checked easily, and the brake fluid is not to corrode the related parts of the system.

4.1.11 A vehicle fitted with a split service brake system is to carry a red warning lamp. The lamp lights when the ignition switch is turned on and goes out once the function check is complete. It indicates a hydraulic failure occurring with a control force on the control not greater than 90 N, or a master cylinder reservoir level, with the control not operated, below the higher of the minimum level given in the technical documentation of the vehicle and one half of the reservoir capacity. The lamp keeps indicating for as long as the fault is present and the ignition switch is in the on position.

4.1.12 During and after the test, the friction material is not to separate from the shoe, and in the case of a hydraulic brake the brake fluid is not to leak.

4.2.1 A four-wheel all-terrain vehicle (ATV) is to have separately operated front and rear braking systems, or one split braking system, or one combined brake system controlling the brakes on all wheels together with a secondary brake system that may be the parking brake system. The control of the separately operated front brake system is a brake lever on the right handlebar, and the separately operated rear brake system is operated by a foot pedal at the right footrest; on vehicles without a clutch lever a brake lever on the left handlebar may be used. When braking with a hand lever, the hand is not to leave the handlebar. Where a combined brake system is used, the vehicle is to have a secondary brake system, which may be the parking brake system, but whose control and transmission device are not to be the same as those of the service brake.

4.2.1.6 A four-wheel all-terrain vehicle meeting any one of the following conditions is to be fitted with a split service brake system or a combined service brake system operated by a foot pedal, together with a secondary brake system that may be the parking brake system: kerb mass over 350 kg, the battery mass being excluded for electric drive; maximum design speed over 50 km/h; engine cylinder capacity over 50 cubic centimetres; maximum net power output over 4 kW, or maximum continuous rated power over 4 kW for electric drive.

4.2.2 A multi-purpose all-terrain vehicle (UV) and a go-kart are to be fitted with a split service brake system or a combined service brake system operated by a foot pedal, and also with a secondary brake system that may be the parking brake system.

4.3.1 Whatever the speed, the load and the uphill or downhill gradient, the service brake system is to control the vehicle and bring it to a safe, rapid and effective stop, the braking action being progressive; the vehicle is to be built so that the driver can operate the control easily from the normal driving position without taking both hands off the steering wheel or handlebar.

4.3.2 If the service brake system fails, the secondary brake system is to stop the vehicle within a suitable distance with a progressive action, the driver keeping at least one hand on the steering wheel or handlebar from the normal driving position.

4.3.3 The parking brake system is to lock the working parts by purely mechanical means so that the vehicle stays on an uphill or downhill slope even when the driver has left it; the driver is to be able to operate it from the seat, and it is to have a separate control, distinct from that of the service brake system.

5 Braking system tests and performance requirements

5.1 The braking system tests and performance requirements for category Y four-wheel all-terrain vehicles and category Y go-karts follow Annex A.

5.2.1.1 Performance of the service brake system, the secondary brake system included, is judged from the braking distance and/or the mean fully developed deceleration, measured under the stated conditions at the corresponding initial speed. The test speed is to be within +/-5 km/h of the specified value, and a corrected distance is used where the actual speed departs from the specified one; the document gives the equation for the braking distance at the actual speed, the equation for the corrected braking distance and the equation for the mean fully developed deceleration, with braking distance in metres, vehicle speed in kilometres per hour and a variable fixed by the particular test.

5.2.1.2 The instruments for control force and deceleration are to record both continuously; speed and distance instruments are to be accurate to within 1 %; the braking force instrument is to record the maximum value and the maximum difference during the build-up of braking force, with an accuracy within 5 %.

5.2.1.3 The test area for dynamic braking tests is to be level, clean and dry, with a good coefficient of adhesion and a gradient not greater than 1 %. The test lane width is 2.5 m plus the width of the vehicle. Parking brake tests are run on a plane slope of 18 % gradient that is clean, dry and does not deform under the weight of the test vehicle.

5.2.1.4 Ambient temperature is 4 °C to 45 °C and wind speed does not exceed 5 m/s.

5.2.1.5 Tyres are inflated to the pressure specified by the manufacturer for the rated load condition, the vehicle is set to its normal running condition, tyre wear does not exceed 20 % of the tread depth, the load is distributed as required by the manufacturer and stated in the test report, and removable speed limiters are removed while adjustable ones are set to allow the maximum speed to be reached.

5.2.1.6 The driver mass is 75 kg and the driver keeps the same normal driving position throughout. Each braking application starts with the vehicle in the middle of the test lane, and performance is measured without wheel lock, without the vehicle leaving the lane and without abnormal vibration. The control force is not to exceed the maximum specified for the vehicle type. Vehicles with an automatic gearbox complete all the braking performance tests whether the condition is engine disconnected or engine connected, and where the automatic gearbox has a neutral position it is put in neutral for the engine disconnected condition. Unless otherwise stated, the brake temperature at the start of each application is between 55 °C and 100 °C, measured with a rubbing thermocouple at the centre of the outer surface of the disc or drum. Unless otherwise stated, the test speed is the lower of 40 km/h and 90 % of V max for a maximum speed of 50 km/h or less, and the lower of 60 km/h and 90 % of V max above 50 km/h. Unless otherwise stated, braking is repeated until the performance is met, up to a maximum of six applications. Initial brake temperature, initial speed, average control force, braking distance and mean deceleration are recorded.

5.2.1.7 For a brake lever the control force is applied to the front face of the lever, in the plane of rotation, perpendicular to the axis joining the pivot and the outermost point of the lever, at a point 50 mm from that outermost point; for a brake pedal it is applied at a suitable angle at the centre of the pedal. The average control force on a service brake control is not greater than 200 N by hand, and by foot not greater than 350 N for four-wheel all-terrain vehicles and not greater than 500 N for multi-purpose all-terrain vehicles and go-karts. On the parking brake it is not greater than 400 N by hand and 500 N by foot.

5.2.2.1.1 The front wheel braking force is to be not less than 60 % of the front axle load and the rear wheel braking force not less than 55 % of the rear axle load.

5.2.2.1.2 Braking force is to be reasonably distributed between the left and right wheels of the same axle, the requirement not applying to left and right wheels mounted on a single rigid axle. The ratio of the greatest difference between the left and right braking forces measured simultaneously during the whole build-up to the greater of the maximum braking forces measured on that axle is not to exceed 20 % on the front axle, and not to exceed 24 % on the rear axle when the rear braking force is at least 60 % of that axle load; where the rear braking force is below 60 % of the axle load, the greatest simultaneous left to right difference is not to exceed 8 % of that axle load. These bench requirements serve as a production assessment, and where performance is disputed the road test braking distance or deceleration prevails.

5.2.2.1.3 After the procedure of 6.2.4, dry braking with the controls applied separately is to meet Table 1: front braking system only, S not greater than 0.1 x V + 0.0087 x V squared and mean fully developed deceleration at least 4.4 metres per second squared; rear braking system only, 0.1 x V + 0.0133 x V squared and at least 2.9; combined brake system (CBS), 0.1 x V + 0.0077 x V squared and at least 5.0; split braking system (SSBS), 0.1 x V + 0.0077 x V squared and at least 5.0; secondary brake system, 0.1 x V + 0.0154 x V squared and at least 2.5. V is the specified test speed in kilometres per hour and S is in metres.

5.2.2.1.4 For vehicles meeting any of the four thresholds of kerb mass, design speed, cylinder capacity or power output, dry braking with the controls applied together, run to 6.2.5, is to give a braking distance not greater than 0.0060 x V squared, in metres, with V in kilometres per hour.

5.2.2.1.5 In the high speed test of 6.2.6, the mean fully developed deceleration is to be at least 5.8 metres per second squared, or the braking distance not greater than 0.1 x V + 0.0067 x V squared.

5.2.2.1.6 In the wet braking test of 6.2.7, the average deceleration measured to 6.2.7.4.3 is to be at least 60 % of the corresponding value of the baseline test and the maximum deceleration measured to 6.2.7.4.4 is not to exceed 120 % of the corresponding baseline value.

5.2.2.1.7 In the fade test of 6.2.9, the mean fully developed deceleration is to be at least 60 % of the value recorded in 6.2.9.3, or the corrected hot braking distance is to satisfy the relation given in the document between the corrected baseline distance of 6.2.9.3, the corrected hot distance of 6.2.9.5 and the specified test speed.

5.2.2.2 After the secondary brake has been tested under the corresponding conditions, its performance is to meet Table 1.

5.2.2.3 With the vehicle parked nose up and nose down, the parking brake system is to hold it stationary on an 18 % slope for 5 min.

5.2.2.4 Failure of the split service brake system, of the power-assisted braking system and of the combined brake system is covered by Annexes B, C and D respectively.

6 Test methods

6.1 Test methods for category Y four-wheel all-terrain vehicles and category Y go-karts follow Annex A.

6.2.1 Table 2 sets the test order for the other categories: brake burnishing (6.2.2); braking force test (6.2.3); dry braking with the controls applied separately (6.2.4); dry braking with the controls applied together (6.2.5); high speed braking test (6.2.6); wet braking test (6.2.7); parking brake system test (6.2.8); fade test (6.2.9), normally run last; partial failure test of the split service brake system (Annex B); failure test of the power-assisted braking system (Annex C); and failure test of the combined brake system (Annex D), the last three being run where applicable.

6.2.2 Burnishing is carried out before the performance assessment and may be done by the manufacturer. The vehicle is in the kerb mass condition with the engine disconnected; the initial speed is the lower of 50 km/h and 80 % of V max and the final speed 5 km/h to 10 km/h; each service control is used on its own; deceleration is 3.0 to 3.5 metres per second squared, or the maximum the vehicle can reach; 100 applications are made for each braking system, the initial brake temperature before each application being not greater than 100 °C.

6.2.3 For the braking force test the vehicle is in the kerb mass condition. The load on the front and rear wheels or axles is measured with the driver seated in the normal riding or driving position. The vehicle is placed on the brake tester with its longitudinal centre plane perpendicular to the roller axis and secured against movement. Vehicles with a neutral position are put in neutral, and the left and right wheels of the same axle are tested together on the two rollers. Braking is applied 2 s after the rollers start and increased to the required maximum control force, the left to right difference and the maximum force on each wheel being measured throughout the build-up. Added mass or an equivalent force may be applied to obtain sufficient adhesion, without being counted in the axle load, and measures such as chocks or a tie-down may be used; where the wheels still lock and slip on the rollers, or the vehicle moves back off them, while the braking force remains below the requirement, the road test method of the document is used instead. On a plate-type tester the vehicle is driven onto the plates at 5 km/h to 10 km/h, or the speed recommended by the tester manufacturer, with the gearbox in neutral, an automatic vehicle being allowed a high gear, and braked sharply to a stop while the quantities required by 5.2.2.1.1 and 5.2.2.1.2 are measured. Each wheel is measured three times; the greatest of the three is taken as the maximum braking force of that wheel and the average of the three maximum left to right differences as the maximum difference.

6.2.4 For dry braking with the controls applied separately the vehicle is laden, and vehicles with a combined brake system or a split service brake system are also tested lightly loaded, under the conditions of 5.2.1. Each service brake control is used on its own, combined and secondary braking included. Brake temperature is checked before each run. The vehicle is accelerated along the lane centreline through the normal gears to 5 km/h above the test speed, acceleration is stopped and the engine disconnected, and braking is applied sharply when the speed falls to the test speed, until the vehicle is fully stopped. The run is repeated until the performance is met, up to six times.

6.2.5 Dry braking with the controls applied together is run on lightly loaded vehicles meeting any of the four thresholds, at a test speed equal to the lower of 100 km/h and 0.9 V max. Where two service brake systems are fitted, both controls are operated at the same time; where one is fitted, its control is operated. The approach, braking and repetition follow the pattern of 6.2.4, up to six runs.

6.2.6 The high speed test applies to vehicles whose maximum speed exceeds 125 km/h, lightly loaded, with the engine connected and the gearbox in the highest gear. The test speed is 0.8 V max for a maximum speed above 125 km/h and below 200 km/h, and 160 km/h for a maximum speed of 200 km/h or more. Both service brake controls are operated together where two systems are fitted, brake temperature is checked before each run, and the approach and repetition follow the pattern of 6.2.4, up to six runs.

6.2.7 The wet braking test does not apply to the parking brake system unless it is also the secondary brake system, nor to drum brakes or fully enclosed disc brakes unless these have ventilation or inspection holes. For each braking system a baseline dry test to 6.2.4 is run first, then the wet performance is measured with water sprayed continuously on the brake, using the parameters of the baseline test. Mean fully developed deceleration and braking distance do not apply to this test. The vehicle is laden, with vehicles having a combined or split service brake system also tested lightly loaded, and the engine is disconnected. On disc brakes water is sprayed continuously at 15 L/h directly onto the rotating disc; where a shield or guard is fitted the water is directed at the disc face 45° ahead of it, and where the specified position cannot be used or coincides with a ventilation hole the spray is moved along the same radius by up to 90° ahead of it. On drum brakes with inspection or ventilation holes, water is sprayed evenly at 15 L/h on both sides of the drum cover and drum, from a nozzle placed at two thirds of the distance from the outer edge of the drum to the hub centre and at least 15° away from the edge of any ventilation or inspection hole. In the baseline test the control force is adjusted to give a deceleration of 2.5 to 3.0 metres per second squared and three values are recorded: the average control force between 80 % and 10 % of the specified test speed, the average deceleration between 0.5 s and 1.0 s after the start of braking, and the maximum deceleration from the start of braking until 0.5 s before the vehicle stops; three baseline runs are made and averaged. The wet test is run at the same specified speed, with no change to the system other than the spray, braking after 500 m of riding with the average control force found in the baseline test.

6.2.8 The parking brake test is run laden, with the engine disconnected, an initial brake temperature not greater than 100 °C, a road gradient of 18 % and a control force not greater than 400 N by hand or 500 N by foot. The vehicle is parked nose up along the slope on the parking brake and, if it stays stable, timing begins; the procedure is then repeated nose down.

6.2.9 The fade test does not apply to parking or secondary brake systems, nor to vehicles whose maximum speed is not greater than 50 km/h. All braking is done laden with the engine disconnected under the conditions of 5.2.1. For each braking system a baseline dry test to 6.2.4 is run, then a heating sequence, then a hot braking application to 6.2.4. During the heating sequence the vehicle carries equipment recording control force and deceleration continuously, and mean fully developed deceleration and braking distance do not apply to that sequence, whereas the baseline and hot applications are measured. The first heating application starts from a brake temperature between 55 °C and 100 °C. The test speed is the lower of 100 km/h and 70 % of V max for a single front system, the lower of 80 km/h and 70 % of V max for a single rear system, and the lower of 100 km/h and 70 % of V max for a combined brake system. Each service brake system is applied separately. On the first application a constant control force is used to give a deceleration of 3.0 to 3.5 metres per second squared between 80 % and 10 % of the specified test speed, or the maximum the vehicle can reach. Where a manual gearbox or an automatic gearbox that can be disengaged by hand is fitted, the engine is connected in the highest gear keeping the engine above the idle speed declared by the manufacturer from the specified test speed down to 50 % of it, and disconnected from there to standstill. Ten further applications follow with the same control force, 1000 m apart, the vehicle being accelerated at its maximum rate back to the test speed after each stop and held there. The hot application is made within 1 min of the end of the heating sequence, under the baseline conditions and with a control force not greater than that of the baseline test.

6.2.10 The partial failure test of the split service brake system follows Annex B, the failure test of the power-assisted braking system follows Annex C, and the failure test of the combined brake system follows Annex D.

A Annex A (normative) Braking performance requirements and test methods for category Y four-wheel all-terrain vehicles (ATV) and category Y go-karts

A.1.1 Where the rated payload of the vehicle is 97.5 kg or more, the test mass is the kerb mass of the complete vehicle plus 97.5 kg, driver and instruments included; where the rated payload is below 97.5 kg, the test mass is the kerb mass plus the rated payload, driver and instruments included. Anything fixed to the seat or the load area is counted in the added mass. Tyres are inflated to the pressure specified by the manufacturer, the ambient temperature is between 4 °C and 45 °C, the wind speed does not exceed 5 m/s, and the test surface is level, clean, dry, with a good coefficient of adhesion and a gradient not greater than 1 %. Removable speed limiters are removed and adjustable ones set to allow the maximum speed. The instruments record control force and deceleration continuously, and speed and distance are measured to within 1 %.

A.1.2 The maximum speed is measured first in order to fix the braking test speed, which is a multiple of 8 km/h lying 6 km/h to 13 km/h below the measured maximum speed; where the maximum speed is below 16 km/h the test speed is the maximum speed of the vehicle, and for category Y-6 vehicles whose maximum speed is at least 16 km/h the test speed is 16 km/h. The front and rear brakes are burnished for the number of applications recommended by the manufacturer, running at the lower of the braking test speed and 48 km/h and braking front and rear together at a deceleration between 1.96 and 4.90 metres per second squared, the vehicle being accelerated back to speed immediately after each stop. The brakes are then adjusted as set out in the manufacturer instructions. Six braking applications are made front and rear together at the lower of the braking test speed and 48 km/h, followed by four applications at the braking test speed, during which the test speed and the braking distance are recorded. The hand control force is not less than 22 N and not greater than 133 N, and the foot control force not less than 44 N and not greater than 222 N. The lever force is applied to the front face of the lever, in its plane of rotation, perpendicular to the axis joining the pivot and the outermost point, at 25 mm from that point; the pedal force is applied at a suitable angle at the centre of the pedal.

A.1.3 A vehicle whose maximum speed is not greater than 29 km/h is to achieve, in at least one of the four applications, a braking distance in metres not greater than the braking test speed in kilometres per hour divided by 5.28. A vehicle whose maximum speed is above 29 km/h is to achieve, in at least one of the four applications, an average braking deceleration of at least 5.88 metres per second squared, the average braking deceleration in metres per second squared being derived from the braking test speed in kilometres per hour and the braking distance in metres.

A.2 For the parking test the vehicle mass is the kerb mass plus the rated payload defined by the manufacturer, driver and instruments included, together with anything fixed to the seat or load area. Tyres are at the pressure specified by the manufacturer and the surface is clean, dry, undeformed under the weight of the vehicle and at a gradient of 18 %. The parking control force does not exceed the values of A.1.2.6, a parking latch may be locked, and a tilt platform is locked before the test starts. Where the service brake and the parking brake are the same, the service brake is burnished as in A.1.2.2 and the brakes are then adjusted as set out in the manufacturer instructions. The vehicle is parked nose up along the slope and, if it stays stable, timing begins; the procedure is repeated nose down. The parking brake system is to hold the vehicle stationary on the 18 % slope for 5 min in both directions.

B Annexes B, C and D (normative) Failure tests and performance requirements

B Annex B checks the performance of the remaining sub-systems when one hydraulic sub-system of a split service brake system leaks. The vehicle is lightly loaded with the engine disconnected, the initial brake temperature is between 55 °C and 100 °C, the specified test speed is 0.8 V max, the control forces follow 5.2.1.7.3 and 5.2.1.7.4, and no more than six applications are made, one meeting the requirement being enough. Any one sub-system is put fully out of action, the vehicle is accelerated to the specified test speed and braked under the specified conditions, and every sub-system is tested in turn. The mean fully developed deceleration is to be at least 3.3 metres per second squared, or the braking distance not greater than 0.1 x V + 0.117 x V squared, with V in kilometres per hour and S in metres.

C Annex C checks the service brake performance after loss of the assisting power and does not apply to vehicles carrying a second independent service brake system. With the assisting power out of action, each service brake system is tested as in the dry braking test of 6.2.4 with the controls applied separately. Table C.1 requires, for an independent service brake system, a braking distance not greater than 0.1 x V + 0.0143 x V squared or a mean fully developed deceleration of at least 2.7 metres per second squared, and for a combined brake system or a split service brake system a braking distance not greater than 0.1 x V + 0.0154 x V squared or a mean fully developed deceleration of at least 2.5 metres per second squared. Where the power-assisted braking system can be actuated by more than one control, each control on its own is to meet these requirements.

D Annex D checks the service brake performance after failure of the transmission device caused by a fault in a brake hose or cable, and applies only to vehicles with a combined brake system in which different service brake systems share a hydraulic or mechanical transmission. The shared part is put fully out of action and the test is run laden, operating only the control not affected by the failure, as in the dry braking test of 6.2.4. For vehicles meeting any of the four thresholds of kerb mass, design speed, cylinder capacity or power output, Table D.1 requires for front wheel braking only and for rear wheel braking only a braking distance not greater than 0.1 x V + 0.0117 x V squared or a mean fully developed deceleration of at least 3.3 metres per second squared. For other vehicles, Table D.2 requires for front wheel braking only and for rear wheel braking only a braking distance not greater than 0.1 x V + 0.0143 x V squared or a mean fully developed deceleration of at least 2.7 metres per second squared.