To choose the right U-bolts for trucks, you need to judge from four core dimensions: specification & size, material strength, application scenario and compliance standards. The specific selection methods are as follows:
1. Match Specifications and Sizes to Ensure Fitting Installation
The specification of a U-bolt is determined by three core parameters: wire diameter, opening width (pipe diameter adaptation), and total length, which must strictly match the actual installation requirements:
Adapt to pipe diameter/leaf spring width: The inner diameter of the opening must fit the outer diameter of the fixed part (leaf spring, pipeline). If the radian does not match, it will fail to hold tightly and cause fixing failure. For example, to fix a 7.5cm-wide truck steel plate, you need to choose a product with an opening width that adapts to the corresponding size.
Determine wire diameter and length: The thicker the wire diameter, the stronger the load-bearing capacity. Light trucks usually use 16mm diameter, while heavy-duty trucks need thicker specifications. The length should reserve enough thread length according to the installation space (ensure there is still 2-3 threads remaining after screwing into the nut).
Support for special customization: If the vehicle has modification or special size requirements, you can choose a manufacturer that supports custom-made according to drawings to ensure the size accurately meets the national standard tolerance.
2. Select Material Strength According to the Operating Environment
Trucks travel with large bumps and high loads, so material and strength directly determine safety. You should choose according to your needs:
| Material Type | Strength Grade | Features | Applicable Scenarios |
| Carbon Steel (Q235/Q345) | Grade 4.8/8.8/10.9 | Low cost, wide strength coverage, can improve rust resistance by galvanizing | Conventional use scenarios of ordinary light trucks and medium trucks |
| Alloy Steel | Grade 10.9/12.9 | Higher strength and good toughness | Heavy-load scenarios of heavy-duty trucks and long-distance transport trucks |
| Stainless Steel (304/316) | Corresponding strength grade | Extremely strong corrosion resistance | Vehicles driving in coastal areas, chemical areas, or in humid and corrosive environments |
National standards clearly require for commercial vehicle U-bolts: yield strength ≥ 800MPa, surface hardness HRC32-38, and it must pass 72-hour salt spray test without red rust. Priority should be given to meeting this standard when selecting.
3. Match Application Scenarios to Meet Functional Requirements
The core function of truck U-bolts is to fix the suspension leaf spring and stabilize the chassis frame. Different application scenarios have different requirements:
Short-distance light load in urban and rural areas (light trucks): Choosing 8.8-grade carbon steel with hot-dip galvanizing can meet the demand, which is the most cost-effective in daily bumpy scenarios such as transporting building materials and agricultural materials.
Long-distance heavy load (heavy trucks): High-strength alloy steel U-bolts of grade 10.9 and above must be selected to ensure structural stability under large loads and avoid loosening and fracture.
Corrosive environment (coastal/chemical areas): Give priority to 304/316 stainless steel material, or carbon steel with special Dacromet anti-corrosion treatment to improve rust resistance and extend service life.
4. Recognize Compliance Standards to Ensure Product Quality
Truck U-bolts need to meet two core national standards:
The general standard follows JB/ZQ 4321-2006, and commercial vehicles additionally need to meet the strength and anti-corrosion requirements of the national standard GB/T 24425.
Give priority to products provided with third-party test reports to ensure that the strength and hardness meet the acceptance standards, and avoid safety hazards caused by inferior products.
Nearly 20years of professional production experience. Quanzhou Zhongke Autoparts is born a completely company with state-of-the-art machinery, Modernmanufacturing processes and efficient processes that ensure maximum quality inproducts, made with raw material of the highest quality and qualified human resources.
For truck U-bolts inquiries, please contact us via the details below：
Sales Manager : Alex
E-mail : info@zk-autoparts.com
Telephone : 0086-18150553806
Post time: Jun-15-2026