GB 21670-2025 Technical requirements and testing methods for passenger car braking systems English, PDF
1 Scope
This document specifies the structural and functional requirements, test and performance requirements, and requirements for determination of the same type of passenger car braking systems, and describes the corresponding test methods.
This document is applicable to Category M1 vehicles specified in GB/T 15089.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 4094 Symbols for controls, indicators and tell-tales of motor vehicles
GB/T 5345 Road vehicles - Labelling of containers for petroleum-based or non-petroleum-based brake fluid
GB/T 5620 Road vehicles - Vocabulary and definition for braking of automotive vehicles and their trailers
GB 12981 Motor vehicle brake fluids
GB/T 15089 Classification of power-driven vehicles and trailers
GB/T 34590 (all parts) Road vehicles - Functional safety
GB 34660 Road vehicles - Requirements and test methods of electromagnetic compatibility
3 Terms and definitions
For the purposes of this standard, the terms and definitions given in GB/T 5620 and GB/T 34590.1 as well as the following apply.
3.1
braking equipment
all braking systems installed on a vehicle
3.2
braking system
combination of components consisting of control device, transmission device, and brake, designed to gradually decelerate or stop a moving vehicle or to keep a stopped vehicle stationary
3.3
control device
component directly operated by the driver to supply the transmission device with the energy required for braking or controlling
Note: Such energies include the driver's physical strength, energy from other energy sources controlled by the driver, or a combination of different energies.
3.4
transmission device
combination of components located between the control device and the brake, enabling functional connection between them
Note 1: Transmission devices are classified as mechanical, hydraulic, pneumatic, electric or hybrid types.
Note 2: When the braking force is provided or assisted by an energy source other than the driver's physical strength, the energy accumulator is considered as a part of the transmission device.
Note 3: The transmission device has two independent functions: control transmission and energy transmission. When the term "transmission" is used alone in this document, it encompasses both "control transmission" and "energy transmission".
3.4.1
control transmission device
combination of components within the transmission device that control the operation of the brake, featuring control function and the required energy accumulator
3.4.2
energy transmission device
combination of components that supply the energy required for the brake to function, including the energy accumulator required for the brake operation
3.5
brake
component that generates a force opposite to the vehicle's motion tendency
Note: The brakes include friction brakes (where the braking force is generated by friction between two relatively moving components in the vehicle), electric brakes (where the braking force is generated by electromagnetic interaction between two relatively moving but non-contacting components in the vehicle), hydraulic brakes (where the braking force is generated by liquid with relative motion between two components in the vehicle), and engine retarders (artificially enhanced engine brake actuation, with force transmitted to the wheels).
3.6
component of braking system
individual component that can be assembled to constitute a braking system
3.7
graduated/modulatable braking
braking process under brake actuation, during which the driver can manipulate the control device at any time within the normal control range to adjust the braking force with sufficient precision, so that the braking force increases or decreases with the magnitude of the manipulation (monotonic function)
3.8
distribution of mass among the axles
distribution of the gravitational force of the vehicle and its loading mass among the axles
3.9
wheel/axle load
vertical static reaction force exerted by the pavement on one/all wheels of an axle within the contact area
3.10
hydraulic braking system with stored energy
braking equipment powered by pressurized fluid stored in an energy accumulator
Note: The pressurized fluid is supplied by a hydraulic pump equipped with pressure limiting device, with the pressure limit specified by the manufacturer.
3.11
actuation
activation and release of the control device
3.12
electric regenerative braking system
braking system that converts kinetic energy of a vehicle into electrical energy during deceleration
3.12.1
electric regenerative braking control
device that modulates the brake actuation of the electric regenerative braking system
3.12.2
electric regenerative braking system of category A
electric regenerative braking system that does not belong to the service braking system
3.12.3
electric regenerative braking system of category B
electric regenerative braking system that belongs to the service braking system
3.13
traction battery; propulsion battery
battery that provides energy for the power system of an electric vehicle
[Source: GB/T 19596-2017, 3.3.1.1.1.1]
3.14
state-of-charge; SOC
percentage of the currently releasable capacity relative to the available capacity in the electrical storage device (such as battery and super-capacitor)
3.15
phased braking
function where two or more braking sources share a single control device, with priority given to one braking source by delaying the activation of the others, allowing it to strengthen the necessary control actions before the others engage
3.16
automatically commanded braking
function where the electronic control system automatically controls the braking system or the brakes of an axle to brake according to the result of automatic evaluation on vehicle information, so as to decelerate the vehicle
3.17
selective braking
function where the electronic control system automatically activates a single brake to adjust the vehicle state through deceleration
3.18
nominal value
reference braking performance obtained by assigning specific values to the input-output transfer functions of each vehicle braking system, which is used to characterize the relationship between the braking rate that the vehicle itself can produce and the level of braking input variables
Note: The "nominal value" is defined as a characteristic parameter representing the relationship between the braking rate of the vehicle itself and the braking input variables.
3.19
braking signal
logic signal indicating the activation of braking
3.20
emergency braking signal
logic signal indicating the activation of emergency braking
3.21
wheel locking
state where, at a vehicle speed of greater than 15km/h, the rotational speed of a wheel is 0r/min or the wheel's braking slip is 100% for a duration of 100ms or longer (500ms for ABS tests conducted on pavements with a low coefficient of adhesion)
3.22
yaw angle
included angle between the vehicle's centerline when stationary and the reference line of travel
3.23
anti-lock braking system; ABS
system that can automatically control the degree of slip of one or more wheels of a vehicle in the wheels' direction of rotation during braking
3.24
sensor
component that identifies the vehicle's motion state or the wheels' rotation state and then transmits such information the controller
3.25
controller
component that processes the information provided by the sensor and issues commands to the modulator
3.26
modulator
component that modulates the braking force according to commands received from the controller
3.27
directly controlled wheel [ An ABS with select-high control may be considered to include both directly and indirectly controlled wheels. In an ABS with select-low control, all sensor-equipped wheels are considered as directly controlled wheels.])
wheel whose braking force is modulated according to data provided by its own sensor on the vehicle
3.28
indirectly controlled wheel 1)
wheel whose braking force is modulated according to data provided by other wheels' sensors
3.29
full cycling
ABS operation mode where braking force is repeatedly modulated to prevent the directly controlled wheels from locking
Note: This definition is not applicable to single modulation performed during braking until the vehicle comes to a stop.
3.30
electronic control system
combination of a series of units that collaboratively realize vehicle control functions by means of electronic data processing
Note: This system is typically controlled by software and consists of independent functional components such as sensors, controllers, and actuators connected via transmission links. It includes mechanical, electro-pneumatic, and electro-hydraulic units.
3.31
unit
smallest division of system components that can be combined to form a separate identifiable, analyzable or replaceable entity
3.32
transmission links
means of interconnecting internal units for signal transmission, operational data transfer, or energy supply
Note: These are typically electronic, but may also be mechanical, pneumatic, hydraulic, or optical.
3.33
boundary of functional operation
extent of external physical boundaries within which the system can maintain control
3.34
energy source
device that generates and supplies the energy required by the braking system
3.35
electrical storage device
device or combination of devices capable of storing electrical energy and supplying it to the transmission device of the braking system
Note: Multiple electrical storage devices connected in series and/or parallel to supply energy to a single braking circuit are considered as one electrical storage device.
3.36
electrical supply
device that supplies electrical energy to the electrical storage device of the braking system
Examples: Batteries, rechargeable energy storage systems (REESS), generators, fuel cells, or combinations thereof.
3.37
state of an electrical storage device
current capability of an electrical storage device to supply power (W) and energy (Wh)
3.38
performance of an electrical storage device
capability of a fully charged electrical storage device to supply power (W) and energy (Wh)
3.39
electrical transmission braking system; ETBS
braking system where the service braking force and its transmission are solely powered by electrical energy from an electrical storage device controlled by the driver
3.40
brake demand value
demand value for braking on a single wheel or single axle actuated electrically to generate braking force
3.41
effect of ageing
irreversible degradation in the performance of an electrical storage device caused by factors such as time, usage, and environmental conditions
3.42
energy management system
system that monitors key variables affecting the performance and state of an electrical storage device (e.g., voltage, temperature, internal resistance, effect of ageing, SOC, power consumption, and charging cycles) and infers whether the actual capability of the electrical storage device meets the design requirements
Note: The energy management system does not necessarily have to be part of the ETBS but is utilized by it.
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the following symbols apply.
areduced: reduced value of the deceleration demand value
aref: deceleration demand value
B: braking force
BEF: braking effectiveness factor
dm: mean fully developed deceleration
dM: maximum mean fully developed deceleration of a passenger car in an Type-O test with disengaged powertrain
dM+R: calculated mean fully developed deceleration of a passenger car towing an unbraked trailer
Dw: ratio of wheel cylinder inner diameter to piston diameter
Δd: difference between the thickness of a brand new brake lining (maximum brake lining thickness) and the thickness of a completely worn brake lining (minimum brake lining thickness declared by the manufacturer)
Δt: braking cycle period, that is, the time elapsed from the start of one braking event to that of the next one
E: wheelbase
ε: adhesion utilization, that is, the quotient of the maximum braking rate and the theoretical coefficient of adhesion when the ABS is in operation
εH: ε value on pavement with high coefficient of adhesion
εL: ε value on pavement with low coefficient of adhesion
F: braking force
Contents
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
5 Structural and functional requirements
6 Test and performance requirements
7 Test methods
8 Determination of the same type
9 Implementation of this standard
Annex A (Normative) Functional safety requirements for brake electronic control systems
Annex B (Normative) Requirements for functional safety test reports of brake electronic control systems
Annex C (Normative) Requirements for functional safety descriptions of brake electronic control systems
Annex D (Normative) Inspection procedures for SOC of traction batteries
Annex E (Normative) Requirements for braking and running deviation tests of vehicles equipped with temporary spare wheels/tyres
Annex F (Normative) Processing requirements for vehicle parameters and test data
GB 21670-2025 Technical requirements and testing methods for passenger car braking systems English, PDF
1 Scope
This document specifies the structural and functional requirements, test and performance requirements, and requirements for determination of the same type of passenger car braking systems, and describes the corresponding test methods.
This document is applicable to Category M1 vehicles specified in GB/T 15089.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 4094 Symbols for controls, indicators and tell-tales of motor vehicles
GB/T 5345 Road vehicles - Labelling of containers for petroleum-based or non-petroleum-based brake fluid
GB/T 5620 Road vehicles - Vocabulary and definition for braking of automotive vehicles and their trailers
GB 12981 Motor vehicle brake fluids
GB/T 15089 Classification of power-driven vehicles and trailers
GB/T 34590 (all parts) Road vehicles - Functional safety
GB 34660 Road vehicles - Requirements and test methods of electromagnetic compatibility
3 Terms and definitions
For the purposes of this standard, the terms and definitions given in GB/T 5620 and GB/T 34590.1 as well as the following apply.
3.1
braking equipment
all braking systems installed on a vehicle
3.2
braking system
combination of components consisting of control device, transmission device, and brake, designed to gradually decelerate or stop a moving vehicle or to keep a stopped vehicle stationary
3.3
control device
component directly operated by the driver to supply the transmission device with the energy required for braking or controlling
Note: Such energies include the driver's physical strength, energy from other energy sources controlled by the driver, or a combination of different energies.
3.4
transmission device
combination of components located between the control device and the brake, enabling functional connection between them
Note 1: Transmission devices are classified as mechanical, hydraulic, pneumatic, electric or hybrid types.
Note 2: When the braking force is provided or assisted by an energy source other than the driver's physical strength, the energy accumulator is considered as a part of the transmission device.
Note 3: The transmission device has two independent functions: control transmission and energy transmission. When the term "transmission" is used alone in this document, it encompasses both "control transmission" and "energy transmission".
3.4.1
control transmission device
combination of components within the transmission device that control the operation of the brake, featuring control function and the required energy accumulator
3.4.2
energy transmission device
combination of components that supply the energy required for the brake to function, including the energy accumulator required for the brake operation
3.5
brake
component that generates a force opposite to the vehicle's motion tendency
Note: The brakes include friction brakes (where the braking force is generated by friction between two relatively moving components in the vehicle), electric brakes (where the braking force is generated by electromagnetic interaction between two relatively moving but non-contacting components in the vehicle), hydraulic brakes (where the braking force is generated by liquid with relative motion between two components in the vehicle), and engine retarders (artificially enhanced engine brake actuation, with force transmitted to the wheels).
3.6
component of braking system
individual component that can be assembled to constitute a braking system
3.7
graduated/modulatable braking
braking process under brake actuation, during which the driver can manipulate the control device at any time within the normal control range to adjust the braking force with sufficient precision, so that the braking force increases or decreases with the magnitude of the manipulation (monotonic function)
3.8
distribution of mass among the axles
distribution of the gravitational force of the vehicle and its loading mass among the axles
3.9
wheel/axle load
vertical static reaction force exerted by the pavement on one/all wheels of an axle within the contact area
3.10
hydraulic braking system with stored energy
braking equipment powered by pressurized fluid stored in an energy accumulator
Note: The pressurized fluid is supplied by a hydraulic pump equipped with pressure limiting device, with the pressure limit specified by the manufacturer.
3.11
actuation
activation and release of the control device
3.12
electric regenerative braking system
braking system that converts kinetic energy of a vehicle into electrical energy during deceleration
3.12.1
electric regenerative braking control
device that modulates the brake actuation of the electric regenerative braking system
3.12.2
electric regenerative braking system of category A
electric regenerative braking system that does not belong to the service braking system
3.12.3
electric regenerative braking system of category B
electric regenerative braking system that belongs to the service braking system
3.13
traction battery; propulsion battery
battery that provides energy for the power system of an electric vehicle
[Source: GB/T 19596-2017, 3.3.1.1.1.1]
3.14
state-of-charge; SOC
percentage of the currently releasable capacity relative to the available capacity in the electrical storage device (such as battery and super-capacitor)
3.15
phased braking
function where two or more braking sources share a single control device, with priority given to one braking source by delaying the activation of the others, allowing it to strengthen the necessary control actions before the others engage
3.16
automatically commanded braking
function where the electronic control system automatically controls the braking system or the brakes of an axle to brake according to the result of automatic evaluation on vehicle information, so as to decelerate the vehicle
3.17
selective braking
function where the electronic control system automatically activates a single brake to adjust the vehicle state through deceleration
3.18
nominal value
reference braking performance obtained by assigning specific values to the input-output transfer functions of each vehicle braking system, which is used to characterize the relationship between the braking rate that the vehicle itself can produce and the level of braking input variables
Note: The "nominal value" is defined as a characteristic parameter representing the relationship between the braking rate of the vehicle itself and the braking input variables.
3.19
braking signal
logic signal indicating the activation of braking
3.20
emergency braking signal
logic signal indicating the activation of emergency braking
3.21
wheel locking
state where, at a vehicle speed of greater than 15km/h, the rotational speed of a wheel is 0r/min or the wheel's braking slip is 100% for a duration of 100ms or longer (500ms for ABS tests conducted on pavements with a low coefficient of adhesion)
3.22
yaw angle
included angle between the vehicle's centerline when stationary and the reference line of travel
3.23
anti-lock braking system; ABS
system that can automatically control the degree of slip of one or more wheels of a vehicle in the wheels' direction of rotation during braking
3.24
sensor
component that identifies the vehicle's motion state or the wheels' rotation state and then transmits such information the controller
3.25
controller
component that processes the information provided by the sensor and issues commands to the modulator
3.26
modulator
component that modulates the braking force according to commands received from the controller
3.27
directly controlled wheel [ An ABS with select-high control may be considered to include both directly and indirectly controlled wheels. In an ABS with select-low control, all sensor-equipped wheels are considered as directly controlled wheels.])
wheel whose braking force is modulated according to data provided by its own sensor on the vehicle
3.28
indirectly controlled wheel 1)
wheel whose braking force is modulated according to data provided by other wheels' sensors
3.29
full cycling
ABS operation mode where braking force is repeatedly modulated to prevent the directly controlled wheels from locking
Note: This definition is not applicable to single modulation performed during braking until the vehicle comes to a stop.
3.30
electronic control system
combination of a series of units that collaboratively realize vehicle control functions by means of electronic data processing
Note: This system is typically controlled by software and consists of independent functional components such as sensors, controllers, and actuators connected via transmission links. It includes mechanical, electro-pneumatic, and electro-hydraulic units.
3.31
unit
smallest division of system components that can be combined to form a separate identifiable, analyzable or replaceable entity
3.32
transmission links
means of interconnecting internal units for signal transmission, operational data transfer, or energy supply
Note: These are typically electronic, but may also be mechanical, pneumatic, hydraulic, or optical.
3.33
boundary of functional operation
extent of external physical boundaries within which the system can maintain control
3.34
energy source
device that generates and supplies the energy required by the braking system
3.35
electrical storage device
device or combination of devices capable of storing electrical energy and supplying it to the transmission device of the braking system
Note: Multiple electrical storage devices connected in series and/or parallel to supply energy to a single braking circuit are considered as one electrical storage device.
3.36
electrical supply
device that supplies electrical energy to the electrical storage device of the braking system
Examples: Batteries, rechargeable energy storage systems (REESS), generators, fuel cells, or combinations thereof.
3.37
state of an electrical storage device
current capability of an electrical storage device to supply power (W) and energy (Wh)
3.38
performance of an electrical storage device
capability of a fully charged electrical storage device to supply power (W) and energy (Wh)
3.39
electrical transmission braking system; ETBS
braking system where the service braking force and its transmission are solely powered by electrical energy from an electrical storage device controlled by the driver
3.40
brake demand value
demand value for braking on a single wheel or single axle actuated electrically to generate braking force
3.41
effect of ageing
irreversible degradation in the performance of an electrical storage device caused by factors such as time, usage, and environmental conditions
3.42
energy management system
system that monitors key variables affecting the performance and state of an electrical storage device (e.g., voltage, temperature, internal resistance, effect of ageing, SOC, power consumption, and charging cycles) and infers whether the actual capability of the electrical storage device meets the design requirements
Note: The energy management system does not necessarily have to be part of the ETBS but is utilized by it.
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the following symbols apply.
areduced: reduced value of the deceleration demand value
aref: deceleration demand value
B: braking force
BEF: braking effectiveness factor
dm: mean fully developed deceleration
dM: maximum mean fully developed deceleration of a passenger car in an Type-O test with disengaged powertrain
dM+R: calculated mean fully developed deceleration of a passenger car towing an unbraked trailer
Dw: ratio of wheel cylinder inner diameter to piston diameter
Δd: difference between the thickness of a brand new brake lining (maximum brake lining thickness) and the thickness of a completely worn brake lining (minimum brake lining thickness declared by the manufacturer)
Δt: braking cycle period, that is, the time elapsed from the start of one braking event to that of the next one
E: wheelbase
ε: adhesion utilization, that is, the quotient of the maximum braking rate and the theoretical coefficient of adhesion when the ABS is in operation
εH: ε value on pavement with high coefficient of adhesion
εL: ε value on pavement with low coefficient of adhesion
F: braking force
Contents of GB 21670-2025
Contents
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
5 Structural and functional requirements
6 Test and performance requirements
7 Test methods
8 Determination of the same type
9 Implementation of this standard
Annex A (Normative) Functional safety requirements for brake electronic control systems
Annex B (Normative) Requirements for functional safety test reports of brake electronic control systems
Annex C (Normative) Requirements for functional safety descriptions of brake electronic control systems
Annex D (Normative) Inspection procedures for SOC of traction batteries
Annex E (Normative) Requirements for braking and running deviation tests of vehicles equipped with temporary spare wheels/tyres
Annex F (Normative) Processing requirements for vehicle parameters and test data
