What to Check in Automotive Leaf Springs for Heavy Vehicles

At Yutian Qianjin Automobile Suspension Co., Ltd., we produce the automotive leaf springs that carry the load on trucks, trailers and other heavy vehicles. The ER0003200202 assembly is a two-leaf multi-leaf spring made from SUP9 steel in a 28 by 90 mm flat section, with a working length of 1800 mm and a total assembly weight of 61.94 kg. It is built to GB/T 19844-2005 and finished with a black anti-rust paint for protection during storage and service.

Material and Heat Treatment

SUP9 is a spring steel chosen for parts that must flex without taking a permanent set. The leaves are formed and heat treated to a hardness of HBW 375 to 444, a range that gives the spring enough strength to carry its rated load while keeping the toughness needed for repeated deflection. The first and second leaves are formed with ears at both ends and produced by a long taper rolling process. A rubber composite gasket is fitted between the ends of the two leaves to reduce wear and noise at the contact points.

Dimensions and Tolerances

The assembly has a straight length of 1800 mm with a tolerance of plus or minus 3 mm. The main position is controlled at 900, 740 and 680 mm with tolerances between 1.5 and 5 mm, the centre hole is 15 mm with a plus 0.35 mm allowance, and the half taper length is 1152 mm with a tolerance of 1.5 mm. The product camber is 132 mm with a tolerance of 5 mm. These figures matter because the spring has to sit correctly in the hanger and the axle seat without introducing a side load or a change in ride height.

Assembly and Surface Protection

Graphite grease is applied between the leaves so they can slide as the spring deflects, which reduces internal friction and helps the ride stay consistent. The complete assembly is then coated with black anti-rust paint. The paint protects the steel during transport and in service, but it is not a substitute for checking the spring after installation. A damaged coating should be touched up, because a bare steel surface will start to rust in wet or salty conditions and the rust can spread between the leaves.

Fitting and Load Considerations

Before fitting, confirm the assembly number and the vehicle application. Check the centre bolt, the U-bolts, the hanger pins and the shackle for wear, because a new spring on worn mounts will not perform as intended. Tighten the U-bolts to the specified torque and recheck them after the first period of service. The load on the spring should stay within the vehicle rating; an overloaded spring can flatten, crack or break a leaf. If the vehicle carries a constant heavy load, the suspension specification should be reviewed rather than compensated with a stiffer spring alone.

Inspection and Replacement

Look for cracks at the centre hole, the ear and the taper, and check for a leaf that has shifted or a clip that has opened. Rust between the leaves is a sign that water has entered the assembly and the grease has dried out. A spring that has lost its camber will sit lower and may cause tyre wear or handling changes. When one side is replaced, the opposite side should be checked as well, because a mismatched pair can make the vehicle sit unevenly and load one side harder.

Working With Qianjin

Our product range covers leaf springs, control arms and shock absorber springs for passenger cars, trucks, trailers and commercial vehicles. Buyers who need automotive leaf springs for a fleet, a repair workshop or a distribution range can send the assembly number, the vehicle model and the quantity. Our team will confirm the material, the dimensions and the packing before quoting. If a part number is not in the current list, a drawing or a sample photo helps us check whether a matching spring can be produced.

Send us the assembly number and the vehicle details, and we will reply with the recommended spring, the quotation and the next steps. A clear reference at the start helps avoid a spring that fits the hanger but does not match the load or the ride height, and it lets us confirm the packing for the shipment.

WhatsApp/Wechat: +86-17731582166

E-mail: qjautospring@gmail.com

Address: Southeast of Xiangtongyuan Village, Gushu Town, Yutian County, Tangshan City, Hebei Province