Siapupy Trailer Shackle & Leaf Spring Kit for 3,500–7,200 lb Axles — Tandem-Axle Complete Hardware

Siapupy Heavy-Duty Trailer Shackle Leaf Spring Kit supplies a complete set of equalizers, shackle straps, bushings, bolts and locking nuts engineered to replace or repair double-eye trailer leaf spring suspensions on 3,500–7,200 lb axles.

This all-in-one trailer axle suspension kit is designed for utility trailers, boat trailers and cargo trailers where double-eye leaf springs are used. The kit brings together corrosion-resistant steel hardware, precision-fit bushings and lock nuts so you can service a tandem-axle suspension in a single repair session. Components are sized to match common OEM hole spacing and thread standards for straightforward installation in home garages or professional shops.

What parts are included and how many of each come in the kit?

The kit contains a full complement of components needed to replace both shackles and equalizers on tandem axles. Quantities are balanced for two-axle trailer setups so you have the parts required to service both sides without sourcing extras.

• 2 long triangular equalizers (7-3/4" hole spacing)
• 8 shackle straps (4.38" length, 3-1/8" hole spacing)
• 8 nylon leaf spring bushings (9/16" I.D., 11/16" O.D.)
• 14 shackle bolts (3-3/8" long) and 14 locking nuts (9/16"-18 threads)

How does this kit fit common trailer suspensions?

Siapupy matched the dimensions to widely used double-eye leaf spring systems so the parts drop into many OEM and aftermarket hanger configurations. Hole spacing, bolt length and thread sizes conform to familiar trailer standards, reducing the need for drilling or custom alteration.

• Equalizer center-to-center hole spacing: 7-3/4"
• Shackle strap length: 4.38" with 3-1/8" hole spacing
• Bushing inner/outer diameters sized for standard shackle bolts
• Bolt and nut thread: 9/16"-18, common on trailer hardware

What materials and finishes are used to resist wear and corrosion?

Key pieces are stamped or formed from steel and finished with an anti-rust coating to extend service life in wet or coastal environments. The bushings are nylon to reduce metal-on-metal wear and quiet movement between assembly parts.

• Steel equalizers and shackle straps with corrosion-resistant coating
• Nylon leaf spring bushings for reduced friction and wear
• Locking nuts designed to maintain clamp under vibration
• Hardware sized and hardened for trailer suspension loads

How does the locking nut design help secure the assembly?

The supplied lock nuts use a deformation-based locking geometry that compresses from both ends, slightly expanding the center threads. This creates friction in the thread interface so fasteners stay put under road vibration and changing loads.

• Lock nuts expand center threads for mechanical locking
• Resists loosening from road vibration and bouncing
• Compatible with the included 3-3/8" shackle bolts
• Helps maintain correct clamp without additional locking compounds

Who is this for: The Siapupy Heavy-Duty Trailer Shackle Leaf Spring Kit is suited for DIY mechanics, trailer service shops and fleet owners who need a reliable replacement kit for double-eye spring tandem axles rated between 3,500 and 7,200 lbs. If you maintain utility, boat or cargo trailers and want a coordinated set of equalizers, shackles, bushings and hardware that match common trailer specifications, this kit streamlines repairs and reduces trips to the parts counter.