Aupar Trailer U-Bolt Kit for 3" Round Axles — 7" Long 1/2" Dia, Includes Tie Plates & Locking Hardware

This Aupar kit contains the hardware needed to fasten a 3-inch round axle to 1-3/4" leaf spring assemblies on trailers rated roughly in the 5,200–7,000 lb range. Engineered for trailer use, the set includes two U-bolts, four tie plates sized for common leaf springs, lock nuts, and spring washers to resist loosening from vibration. Components are built from high-grade steel and finished for durability so you can replace worn mounting hardware or perform an axle rebuild with parts sized to fit popular axle brands.

Will these U-bolts fit my trailer axle and springs?

They are made specifically for 3" round axles and 1-3/4" leaf spring packs, with U-bolt legs 7" long and 1/2" in diameter. Confirm your axle outside diameter and spring plate width before ordering to ensure a correct match.

• U-bolt internal diameter: for 3" round axles
• Leg length: 7" to accommodate typical spring stacks and plates
• Thread size: 1/2" diameter nuts supplied
• Included tie plates sized for 1-3/4" leaf springs

How does the kit resist loosening under road vibration?

Aupar includes upgraded spring washers and lock nuts to reduce the risk of fastener back-off from vibration and load cycling. The washers bite slightly and maintain clamping force while the improved plate shape spreads load more evenly across the clutch points.

• Spring washers that help hold torque under vibration
• Lock nuts supplied for additional thread security
• Redesigned tie plates for uniform pressure distribution
• Steel construction provides consistent clamp strength

What construction and finish should I expect?

The kit is manufactured from high-quality steel for strength and longevity, with a corrosion-resistant finish suitable for trailer environments. These materials deliver the stiffness and load-bearing capacity required for axle mounting while helping slow surface rust in typical road conditions.

• High-grade steel U-bolts and plates for strength
• Protective finish to resist moisture and road debris
• Precision threads for reliable nut engagement
• Robust plate design to reduce local deformation

How easy is installation and what hardware is included?

Installation is straightforward for anyone familiar with trailer axle work: lift and support the trailer, position plate and spring, fit U-bolts over axle and through plate, then torque the nuts to spec. The kit includes everything needed for a two-U-bolt axle clamp on one side of an axle.

• Two 7" U-bolts with 1/2" diameter legs
• Four tie plates sized for 1-3/4" springs
• Locking nuts and spring washers included
• Hardware quantity suited for one axle end (two U-bolts total)

Who is this for: The Aupar Heavy Duty Trailer U-bolt Kit is aimed at trailer owners, DIY mechanics, and small fleet maintainers replacing worn axle clamps or upgrading mounting hardware on 3" round axles paired with 1-3/4" leaf springs. It's a practical match for common axle brands used in light-to-medium duty trailers when you need reliable, trailer-specific mounting hardware that balances strength, corrosion protection, and vibration resistance.