Interpretation of the New GB 7258 Standard for Trailers Equipped with Disc Brakes and Stake‑Side Trailers
2017-11-08
The vehicle braking system (brakes) is a critical component for driving safety. The forthcoming standard GB 7258-2017 introduces new requirements mandating the installation of disc brakes on the front wheels of hazardous‑material transport vehicles, as well as on hazardous‑material transport semi‑trailers and three‑axle flatbed and stake‑body trailers.
Although the new version of GB 7258 has been in effect since January 1, 2018, it provides transitional periods for different provisions: starting January 1, 2019, newly manufactured semi‑trailers used for the transport of dangerous goods must be equipped with disc brakes; and beginning January 1, 2020, newly produced flatbed and stake‑body semi‑trailers must also be fitted with disc brakes.
— Added the requirement that all wheels of semi‑trailers for the transport of dangerous goods, as well as three‑axle platform and stake‑side semi‑trailers, shall be equipped with disc brakes (see 7.2.6).
7.2.6 The original text reads as follows: All wheels of automobiles (excluding three-wheeled vehicles), motorcycles (excluding sidecar motorcycles), and trailers (excluding trailers with a gross vehicle mass not exceeding 750 kg) shall be equipped with brakes. In addition, all dedicated school buses and freight vehicles transporting dangerous goods shall have disc brakes on their front wheels; likewise, the front wheels of other passenger vehicles with a length exceeding 9 meters, as well as all wheels of semi‑trailers used for transporting dangerous goods and of three‑axle platform‑type and cage‑type semi‑trailers, shall be equipped with disc brakes.
Front wheels of hazardous materials transport vehicles and trailer equipped with disc brakes.
This regulation explicitly mandates that the front axle of tractor units transporting dangerous goods, the trailer axle, and the front axle of single vehicles must all be equipped with disc brakes. Compared with the drum brakes that are widely familiar today, many truck drivers remain skeptical about disc brakes.
Compared with drum brakes, disc brakes have a flat braking surface that dissipates heat from both sides, and their central ventilation cavity further enhances cooling. The rotating disc cools readily, making significant deformation less likely and ensuring more stable braking performance. In contrast, drum brakes rely on single-sided heat transfer, resulting in a large temperature differential between the inner and outer surfaces, which can cause the brake drum to deform. Moreover, after prolonged braking, the high temperatures can lead to carbonization of the brake pads, reducing the coefficient of friction and diminishing braking effectiveness.
Because hazardous‑goods transport vehicles carry cargoes that are either flammable and explosive or highly toxic and corrosive, they place stringent demands on the compatibility between the tractor and the trailer. Trailers equipped with disc brakes, working in tandem with auxiliary braking systems such as ABS and hydraulic retarders, ensure smooth and reliable vehicle‑wide braking performance, thereby enhancing the safety of hazardous‑material transport vehicles.
Although there are no specific regulations governing the rear-axle brakes of tractor units and single-unit vehicles used for transporting hazardous materials, the most effective way to ensure consistent braking performance and response times across the entire vehicle is to equip all wheels with disc brakes. This requirement has been enforced for newly manufactured vehicles since January 2019.
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