Dually Wheel Mechanism Types and Their Applications

Dually wheels refer to configurations where two wheels are mounted close together on a single axle end, doubling the load-carrying capacity and enhancing stability. This setup is common in heavy-duty trucks, construction equipment, agricultural machinery, and industrial casters. The design helps distribute weight more evenly, improves traction, and provides greater safety when hauling heavy loads.

Types of Dually Wheel Mechanisms

There are several distinct types of dually wheel mechanisms, each with unique features influencing durability, performance, and suitability for particular applications:

• Standard Dual Wheels: This is the simplest form where two wheels are mounted side-by-side on a single hub or axle flange. The wheels are identical in size, and the setup increases load capacity and surface contact area.
• Straddle Dual Kits: In this configuration, the dual wheels have an inner and outer wheel. The inner wheel is mounted to the vehicle hub, and the outer wheel is mounted to the inner wheel via a secondary bolt circle diameter (PCD). This creates a “straddle” effect and is common in 4WD tractors and heavy equipment. This design reduces stress on wheel discs, minimizing cracking issues experienced in other types.
• Expanded-Band Straddle Dual Kits: These kits feature two wheels with larger offsets, thicker and flatter discs, and a tube-style expander band connecting them. This is the most durable dual wheel option, eliminating cracking and boosting structural integrity. These are often found on heavy-duty industrial vehicles and specialized tractors.

Components of Dually Wheel Assemblies

Key components include:

• Wheels: Made from steel, aluminum, or composite materials depending on application, offering a balance between weight and strength.
• Axle or Hub: Serves as the mounting point for the wheel assemblies.
• Spacers or Bands: Used in expanded straddle setups to achieve larger offsets, offering greater clearance.
• Bolts and Fasteners: Secondary PCD bolts attach the outer wheel to the inner wheel, ensuring secure pairing.
• Swivel Mechanisms: In caster applications, these allow 360-degree rotation for maneuverability.

Advantages of Dually Wheels

• Load Distribution: Two wheels share the load, reducing tire stress and improving longevity.
• Enhanced Stability: Wider wheel stance lowers center of gravity, reducing roll risk during towing or cornering.
• Improved Traction: Dual contact patches increase grip on rough or slippery surfaces.
• Reduced Tire Wear: Load spread leads to more even tire wear, saving maintenance costs.

Applications

• Heavy-Duty Trucks: Used on rear axles to increase towing capacity, common in pickups like the 1-ton or 2-ton dually pickups.
• Agricultural Machinery: Tractors with straddle dual wheels can navigate soft ground while preserving soil structure.
• Construction Equipment: Use expanded-band duals for durability under rough, heavy loads.
• Industrial Casters: Dual wheel casters improve load capacity for moving heavy machinery indoors with enhanced maneuverability.

Maintenance and Recommendations

• Regular inspection of bolt torque on dual assemblies prevents loosening.
• Monitor tire wear to ensure balanced load across all wheels.
• Use appropriate tire inflation for dual setups; uneven pressure can cause premature wear.
• For expanded-band straddle kits, check for corrosion or damage to bands and spacers.

Interesting Industry Notes

A notable case involved a large European farming cooperative switching exclusively to expanded-band straddle dual wheels after frequent wheel cracking issues with standard duals. The upgrade improved machine uptime and lowered replacement costs significantly.

In truck fleets, dually wheel usage has become key for hauling heavier loads safely, especially with the rise of commercial electric trucks requiring reinforced wheel assemblies to support battery weight.

Terminology

• PCD (Pitch Circle Diameter): The diameter of the circle that passes through the center of all the bolts securing wheels.
• Offset: The distance the wheel mounting surface is from the centerline of the wheel; influences how far wheels sit inward or outward.
• Straddle Dual: Dual wheel configuration involving two sets of mounting points to reduce stress on wheels.
• Caster: A wheel mounted on a rotating swivel to allow omnidirectional movement.

This comprehensive overview explains dually wheel mechanism types, their key components, applications, and maintenance tips, helping industries select and maintain the best wheel arrangements for safety, efficiency, and longevity.