Lightweight Aluminum Alloy Wheel End Assembly for Semi-Trailers

1. Product Overview

The wheel end assembly is the rotating assembly that connects the wheel to the axle and carries the load. It consists of the hub, bearing, oil seal, and axle nut, and is equipped with braking components such as a brake disc or brake drum. It is a core component of commercial vehicles.

The high‑strength lightweight aluminum alloy wheel end assembly uses an ultra‑light aluminum‑based material combined with precision manufacturing and assembly technologies. The product is lightweight, durable, has excellent heat dissipation performance, and is convenient for maintenance, matching the lightweight development trend of commercial vehicles. With current policy guidance and clear market demand, aided by large‑scale production and technological innovation, the product is expected to achieve positive economic and social benefits.

The aluminum alloy wheel end assembly produced by Shandong Zonxin Auto Parts Co., Ltd. is the first product in China successfully applied in the commercial vehicle field. The structural design is independently innovated, filling a domestic gap; material selection meets international standards to ensure the quality requirements of global customers.

2. Product Introduction

(1) Aluminum Alloy Wheel Hub (ZL270LF)

Shandong Zonxin Auto Parts Co., Ltd. pioneered the application of ZL270LF aluminum alloy material for manufacturing commercial vehicle wheel hubs. Through optimized design, the product achieves lightweight, high strength, excellent heat dissipation, and strong resistance to thermal fade. This product has entered mass production and sales with favorable market feedback.

1) Material

A new lightweight, high‑strength cast aluminum alloy ZL270LF replaces QT450 (cast iron) material.
ZL270LF aluminum alloy overcomes the shortcomings of traditional cast aluminum alloys—low elongation and inability to be forged or extruded, poor fluidity, and performance decline after casting. It is a new high‑strength material that integrates the advantages of cast aluminum alloys and wrought (deformable) aluminum alloys. The material is castable, forgeable, and extrudable, breaking the boundary between cast and wrought aluminum alloys. This development is domestically pioneering and internationally advanced.

2) Structure

Based on the existing structure, two additional rows of reinforcing cooling ribs were added to improve ventilation and surface cooling efficiency, fully resolving the hub overheating issue during operation. The design has obtained 1 national utility model patent and 6 national industrial design patents.

3) Process

Low‑pressure aluminum alloy casting blank → T6 solution treatment → rough machining → finish machining → surface treatment

4) Assembly

Parts cleaning → servo detection of bearing height difference → hub‑bearing clearance inspection → hub preheating → pressing in bearing outer ring → pressing in oil seal and ABS tone ring → assemble spacer → measure and inspect bearing running clearance → final installation.

Due to the difference in thermal expansion coefficients between aluminum alloy and steel parts, the fit dimensions between the bearing and the hub bore are significantly affected by temperature. After verifying the machining tolerances for the hub inner bore, a special pressing process was adopted to address bearing walk problems under large interference fits. The production line is equipped with high‑precision displacement sensors with a reciprocating precision error ≤ 0.015 mm, allowing precise control of hub running clearance. Compared with traditional processes, this method reduces hub running clearance by 60% and increases service life by 300%.

5)Temperature Performance Parameters

Using the ZL270LF aluminum alloy hub, the wheel-end temperature rises only 30°C above the ambient temperature, which is significantly better than the 60°C rise of traditional hubs, achieving a 50% reduction in wheel-end temperature. This greatly reduces the safety risks caused by wheel-end overheating and completely eliminates the problem of wheel-end fires.

6) Weight

The ZL270LF aluminum alloy disc hub reduces weight by 10.5 kg compared with the QT450 disc hub (a 43% reduction); for a three‑axle semi‑trailer, the total vehicle weight reduction is 63 kg. The ZL270LF aluminum alloy drum hub reduces weight by 12.7 kg compared with the QT450 drum hub (a 56% reduction); for a three‑axle semi‑trailer, the total vehicle weight reduction is 76.2 kg.

7) Product Benefits

Assuming a semi‑trailer transport cost of approximately RMB 0.35 per ton‑km, a daily driving distance of about 450 km, and an annual utilization of about 300 days, a three‑axle semi‑trailer equipped with aluminum alloy hubs (reducing vehicle weight by 76.2 kg per vehicle) can achieve additional income of approximately RMB 3,600 per year.

(2) Aluminum Ceramic Brake Disc (Aluminum matrix composite with varying SiC volume fractions)

Shandong Zonxin Auto Parts Co., Ltd. was the first to apply aluminum‑ceramic brake discs to commercial vehicles and optimized the connection method between the brake disc and the hub. Aluminum‑ceramic brake discs are lightweight, wear‑resistant, corrosion‑resistant, and have a long service life, significantly outperforming traditional HT250 cast iron brake discs.

1) Material

Aluminum‑ceramic (an aluminum‑based composite with varying silicon carbide volume fractions) replaces HT250 (cast iron).

The raw materials for aluminum‑ceramic brake discs are aluminum powder and silicon carbide powder, formed and sintered by powder metallurgy processes and then machined.

2) Structure

The traditional I‑section (I‑beam) disc structure was changed to a flat disc structure to reduce material usage and weight. This domestic innovation has obtained 1 national utility model patent.

3) Process

Mixing → mold pressing → sintering → shaping → rough machining → finish machining → inspection

The powder metallurgy process controls different sintering temperatures at different stages to enhance material mechanical properties.

4) Assembly

The aluminum‑ceramic brake disc is fastened to the hub flange surface by guide sleeves and bolts, effectively reducing the vertical overlapping portion of traditional I‑section discs.

5)  Performance Indicators

Static torsional strength: Under a braking torque load of 22,000 Nm, the maximum stress is 112 MPa; the inner surface of the connection holes also experiences 112 MPa. At 260°C the safety margin is 1.2.

6) Wear, Corrosion, and Service Life

Aluminum‑ceramic brake discs wear 0.08 mm per 10,000 km, a 72% reduction compared to HT250 cast iron discs (0.28 mm/10,000 km), meeting Euro 7 requirements. Service life is approximately 500,000 km—an increase of 235% compared with HT250 discs (~150,000 km). Using a maintenance‑free installation process, maintenance‑free mileage reaches 300,000 km, a 500% improvement over HT250 discs. Salt spray tests (72 h) show only slight corrosion.

7)Weight

Total vehicle weight savings for aluminum‑ceramic brake discs: 117 kg (based on a 13T three disc‑axle semi‑trailer).

8) Temperature Performance

According to GB12676‑2014 'Technical Requirements and Test Methods for Brake Systems of Commercial Vehicles and Trailers', under continuous 20 braking cycles with a braking interval of 60 s, initial speed 60 km/h, and braking deceleration set to 3 m/s²:
• Unloaded (empty): maximum temperature 75°C
• 40% load: maximum temperature 204°C
• 50% load: maximum temperature 246°C
• Fully loaded: maximum temperature 510°C
Using aluminum‑ceramic brake discs, the wheel end temperature rises by only ~30°C above ambient—significantly better than traditional hubs which rise by ~60°C—reducing wheel end temperatures by 50%. This substantially reduces the safety risks caused by wheel end overheating and prevents brake disc high‑temperature cracking when sprayed with water and wheel end fires.

9) Product Benefits

Assuming a semi‑trailer transport cost of approximately RMB 0.35 per ton‑km, a daily driving distance of about 450 km, and an annual utilization of about 300 days, a three‑axle semi‑trailer equipped with aluminum‑ceramic brake discs can reduce vehicle weight by 117 kg per vehicle and achieve additional income of approximately RMB 4,000 per year. Over the full service life of aluminum‑ceramic discs, brake disc replacements can be reduced by two times. For each replacement, labor savings amount to 150 × 6 = RMB 900, parts savings 300 × 6 = RMB 1,800, and parking/replacement downtime loss is approximately RMB 1,400. Two replacements combined save about RMB 8,200. Overall, each vehicle can increase customer benefit by approximately RMB 12,000 per year.

(3) Double-Layer Light Metal Brake Drum

Shandong Zonxin Auto Parts Co., Ltd. developed and designed a double‑metal brake drum using ZL270LF aluminum alloy for the outer layer and aluminum‑ceramic material for the inner layer, employing a company‑invented double‑layer casting process—the world's first of its kind. The product is currently under development.

1) Material:
Outer layer: ZL270LF aluminum alloy (lightweight, high strength, corrosion‑resistant). Inner layer: aluminum‑ceramic (lightweight, wear‑resistant, high‑temperature resistant).

2) Structure:
Double‑layer structure combining the advantages of each material. External ribs/fins are designed for ventilation and cooling to reduce thermal cracking and lower brake shoe carbonization risk.

3) Process:
Double‑layer casting method (dual‑layer pour).

4) Assembly:
Due to differences in thermal expansion coefficients between aluminum alloy and steel parts, the assembly line is equipped with high‑precision displacement sensors with a reciprocating precision error ≤ 0.015 mm to improve service life.

5) Weight

Total vehicle weight savings for double‑layer light metal brake drums: 156 kg (based on a 13T three‑axle drum‑axle semi‑trailer).

6)Temperature Performance

Using double‑layer light metal brake drums, wheel end temperature rises by only ~30°C above ambient—significantly better than the ~60°C rise of traditional hubs—reducing wheel end temperatures by 50%. External rib/fan designs improve ventilation and cooling, mitigating thermal cracking and brake lining high‑temperature carbonization. This effectively eliminates wheel end fire risk.

7)Product Benefits:
Assuming a semi‑trailer transport cost of approximately RMB 0.35 per ton‑km, a daily driving distance of about 450 km, and an annual utilization of about 300 days, a three‑axle semi‑trailer equipped with double‑layer light metal brake drums can reduce vehicle weight by 156 kg per vehicle and achieve additional income of approximately RMB 5,000 per year.

3. Company Profile

Shandong Zonxin Auto Parts Co., Ltd. was established in 2008 and is a national high‑tech enterprise integrating design, R&D, and precision manufacturing. The company has a high‑level professional design and R&D team and advanced production equipment. It currently employs more than 180 people, including over 30 mechanical engineering professionals, with annual sales exceeding RMB 100 million.

Main products include suspension systems, axles, air suspensions, and other special vehicle components. Annual production capacity: 30,000 sets of semi‑trailer mechanical suspension systems, 12,000 air suspension axles, 30,000 drum brake axles, and 12,000 disc brake axles. Products are sold in more than 20 provinces in China and exported to over 10 countries and regions.

The company was among the first in the industry to obtain ISO9001:2008 and ISO/TS16949:2009 quality management system certifications through AQA International LLC (USA). The company has fully implemented 5S lean management and ERP information management. It owns 8 invention patents and more than 70 other patents.

Over the years, the company has followed the development philosophy of being 'innovative, technology‑driven, and service‑oriented'. By combining market realities with customer needs, the company continuously optimizes design and insists on technological innovation. Zonxin Auto Parts looks forward to working with outstanding special vehicle manufacturers for mutual success.

4.Contact Information

Contact: Manager Zhang

Mobile: +86 136 8860 8190

Websitl:www.zonxin.com

Email: eva@zonxin.com

Address: Liangshan County, Shandong Province, China