Brake Tester

Overview

A brake tester is a core piece of equipment used in periodic motor vehicle inspections to evaluate braking performance, with its test readings directly determining whether a vehicle's braking system complies with national safety technical standards. Braking performance serves as the primary benchmark for vehicle safety. Under the national standard "Items and Methods for Motor Vehicle Safety Technical Inspection" (GB 38900), brake testing is a mandatory instrument-based inspection requirement covering critical parameters such as unladen braking efficiency, brake imbalance rate, and parking brake efficiency.

Currently, vehicle inspection centres primarily deploy two types of brake testers: roller counter-force brake testers and plate brake testers. Both variants differ markedly in terms of operating principles, application scenarios, and result representation.

Roller Counter-Force Brake Tester

The roller counter-force brake tester represents the mainstream setup across vehicle inspection centres. It operates on a straightforward principle: the vehicle's wheels are placed on motor-driven roller sets; when the driver depresses the brake pedal, the braking torque generated causes the wheels to exert a counter-tangential reaction force against the rollers. This reaction force is transmitted via a torque gearbox to load cell sensors, and the resulting electrical signals are processed and displayed as braking force readings.

Roller brake testers are broadly categorized by technical origin into Japanese and European designs. Japanese systems typically feature low operating speeds (0.1–0.25 km/h) and smaller rollers (120–180 mm in diameter); earlier units often used slotted steel rollers, offering lower manufacturing costs and good wear resistance, albeit with lower test repeatability. European systems feature higher speeds (2.0–5.0 km/h) and larger rollers (190–300 mm in diameter) with grit-coated surfaces to improve the friction coefficient, delivering superior test stability and higher capacity at the expense of higher build costs and accelerated tyre wear.

In terms of key technical standards, the national standard "Roller Counter-Force Motor Vehicle Brake Tester" (GB/T 13564) sets uniform specifications for roller diameter, centre-to-centre distance, and surface linear speed. The sliding friction coefficient of the roller must not fall below 0.70. To prevent tyre scuffing caused by static friction once wheels lock up against the rollers, the tester must feature an automatic motor cut-off function, typically using a third sensing roller to monitor wheel slip ratio and tripping the drive once maximum braking force is attained.

By measuring the maximum braking force at each wheel, the roller brake tester calculates key indicators such as axle braking efficiency (the ratio of maximum axle braking force to static axle load), total vehicle braking efficiency (the ratio of total maximum braking force across all axles to the gross static axle load), and brake imbalance rate (the maximum difference between left and right wheel braking forces across the same axle during braking).

Plate Brake Tester

The plate brake tester is a low-speed dynamic inertia test platform designed to replicate real-world on-road braking dynamics more closely. During the test, the vehicle is driven onto four test plates at 5–10 km/h, the transmission is shifted into neutral, and emergency braking is applied. Under inertia, the wheels exert an opposing horizontal force onto the plates, causing slight plate displacement while load sensors record real-time variations in braking force and dynamic wheel loads throughout the braking sequence.

The primary advantage of the plate brake tester is its ability to account for dynamic axle load transfer during braking. As forward inertia shifts the vehicle's centre of gravity forward, the front axle load increases while the rear axle unloads—a dynamic behaviour that roller brake testers cannot replicate. The plate tester accurately captures this shift via dynamic weighing. Comparative research indicates that plate brake tester readings reflect the actual on-road capability of the vehicle's brakes more faithfully.

The updated national standard for plate brake testers, "Plate Brake Tester" (GB/T 28529-2025), was released in August 2025 and takes effect on 1 March 2026. The revised standard introduces stricter requirements, including permissible inter-plate wheel load indication errors and plate breakaway force limits, while mandating a braking force sampling frequency of at least 200 Hz.

Comparison Between Both Brake Testers

Overall, roller brake testers remain the preferred option for heavy commercial vehicle lanes and multi-axle vehicle inspections, whereas plate brake testers are ideally suited for passenger car inspection lanes and public transport depot check systems.

Metrological Calibration and Periodic Inspection Requirements

To ensure metrological accuracy, brake testers are periodically calibrated by certified metrology bodies in accordance with statutory verification codes. Roller brake testers are governed by JJG 906-2009 "Verification Regulation of Roller Counter-Force Brake Testers", which permits a braking force indication error within ±3%. Plate brake testers fall under JJG 1020-2007 "Verification Regulation of Plate Brake Testers", which similarly caps the permissible indication error at ±3%.

During periodic vehicle inspections, if readings exceed the tolerance limits defined under GB 7258 and GB 38900, the vehicle fails its braking assessment and must undergo rectifications prior to re-inspection. For vehicles unsuited for roller testers (such as full-time AWD/4WD models), or vehicles that fail roller imbalance limits yet exhibit no noticeable brake pull during dynamic chassis road tests, alternative testing on a plate brake tester or a decelerometer-based road test must be conducted for supplementary verification.