Best Trailer Leaf Spring Kit: 5 Options Compared

If your trailer’s suspension is sagging or you’re upgrading to handle heavier loads, a quality leaf spring kit can make all the difference. These kits typically include springs, U-bolts, hangers, and hardware, saving you the hassle of sourcing parts separately.

This guide compares five top-rated trailer leaf spring kits, covering capacities from 3,500 to 6,000 pounds. Whether you need a complete replacement for a tandem axle or a simple spring swap, you’ll find the right option here.

SEHNSUCHT 4 Leaf Trailer Leaf Spring Kit – Complete Set

The SEHNSUCHT 4 Leaf kit is a comprehensive solution for standard 3,500lb tandem trailer axles. Each spring offers 1,750lbs capacity, with an eye-to-eye length of 25-1/4 inches and a width of 1-3/4 inches. The four-leaf design uses heavy-duty carbon steel for stable transmission and friction damping, plus an extra anti-rust coating to withstand the elements. The kit includes four 5-1/2-inch U-bolts with 1/2-inch threads, two tie plates, and a full hanger kit with equalizers and hangers.

Installation is straightforward for those familiar with trailer suspension, as the kit replaces SW4B springs. The double-eye design ensures a secure fit, and the included hardware covers everything from the axle to the frame. If you’re looking for a complete, ready-to-install set for a 3,500lb axle, this kit delivers solid performance and durability without the need to source extra parts.

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• About The Springs: Each spring offer 1,750lbs capacity, suit for standard 3,500lbs trailer axle. Eye to Eye length: 25-1/4 inch, Free open: 3 inch, width of leaf: 1-3/4 inch, 4 leaves, 9/16 inch bushing dia, 2 Bushings Installed for Each Spring, Leaf Thickness 5/16 inch. NOTE: The nut should be tightened horizontally. Failure to do so will affect the final user experience.
• About The Replacement: It will replace for SW4B. The Leaf Springs Made of Heavy Duty Carbon Steel for transmission stability and friction damping, Extra added anti-rust coating for corrosion resistance and long-lasting performance.
• About The Axle U-bolt Kit: This kit include 4 x 5-1/2" long U bolts, U-bolt thread diameter is 1/2",the curvature (inside diameter) of the U-bolt is 2 4/9"; 2 x tie plates for 1-3/4" leaf springs; 8 x 1/2"-20 hex nuts. And this kit used for 2-3/8" dia round trailer axles.(This product offer 2* U-bolt kit).
• About The Trailer Axle Hanger Kit: This kit include 2 x EQ-E1 equalizers, 6 x 3" tall hangers, 8 x shackle straps, 14 x 9/16"-18 x 3" long shackle bolts and locknuts. And this kit used for 1-3/4" leaf springs.
• After-sales service: Any questions after receiving, please contact us freely. Thanks for choosing us!

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AEagle 4 Leaf Trailer Spring Kit – Corrosion-Resistant Choice

The AEagle 4 Leaf kit is designed as a direct replacement for SW4B springs on 3,500lb trailer axles. Each spring provides 1,750lbs capacity, with a 25-1/4-inch eye-to-eye length, 1.75-inch width, and 3-inch free open. The four-leaf construction features an anti-rust coating for good corrosion resistance, and the springs use high-quality raw materials for strength. The kit includes a U-bolt set for 2-3/8-inch diameter round axles, with four 5-1/2-inch U-bolts, two tie plates, and eight hex nuts.

Installation is simplified by the included hardware, though it’s important to note that this kit only fits round axles, not square ones. The double-eye design with 9/16-inch bushings ensures a snug fit. If you need a reliable replacement for a 3,500lb trailer and want corrosion protection, the AEagle kit offers a straightforward solution with all necessary components for a smooth swap.

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• Replaces for Part Number: SW4B,not fit square axle,Only fit round axle.
• Includes: 2 x 4-Leaves Double Eyes Springs; 3,500lbs axle U-bolt kit for 2-3/8" dia round trailer axles. Kit includes: 4 x 5-1/2" long U bolts, U bolts dia. 1/2", 2 x tie plates for 1-3/4" leaf springs; 8 x 1/2"-20 hex nuts. Complete single trailer axle hanger kit for 1-3/4" leaf springs, Kit includes: 2 x 3" tall hangers, 2 x 2.1" tall hangers, 4 x shackle straps (eye to eye 3.09"), 6 x 9/16"-18 x 3" long shackle bolts and locknuts
• Parameters: 1,750 lb capacity per spring for 3,500 lbs trailers; eye to eye length: 25-1/4 inch, free open: 3 inch, width of leaf: 1-3/4 inch, 4 leaves, 9/16 inch bushing dia, 2 bushings installed for each spring, leaf thickness: 5/16 inch.（Note: The nut should be tightened horizontally. Failure to do so will affect the final user experience）
• Durability: Each of AEAGLE trailer leaf spring kit with anti-rust coating for good corrosion resistance. We always choose raw material with high quality to make our products strong, durable and ensure reliable performance and long use time.
• Quality Assurance: 12-month warranty! Tested before shipping.

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SEHNSUCHT 5 Leaf Trailer Spring Kit – Heavy-Duty Option

The SEHNSUCHT 5 Leaf kit is built for heavier trailers, with each spring offering 3,000lbs capacity for 5,200-6,000lb tandem axles. The five-leaf design uses heavy-duty carbon steel for stability and friction damping, plus an anti-rust coating for longevity. Eye-to-eye length is 25-1/4 inches, with a 3-inch free open and 1-3/4-inch width. The kit includes four 7-inch U-bolts with 1/2-inch threads, two tie plates, and a complete hanger kit with equalizers, hangers, and shackle straps.

This kit replaces SW5 springs and is ideal for trailers carrying heavier loads, such as equipment or large boats. The double-eye configuration ensures secure mounting, and the included hardware covers the axle and frame connections. If you need a robust suspension upgrade for a 5,200-6,000lb trailer, this SEHNSUCHT kit provides the strength and durability required for demanding towing conditions.

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• About The Springs: Each spring offer 3000lbs capacity, suit for standard 5200lbs-6000lbs trailer axle. Eye to Eye length: 25-1/4", Free open: 3", width of leaf: 1-3/4", 5 leaves, 9/16" bushing dia. NOTE: The nut should be tightened horizontally. Failure to do so will affect the final user experience.
• About The Replacement and Material: It will replace for SW5. The Leaf Springs Made of Heavy Duty Carbon Steel for transmission stability and friction damping; Extra added anti-rust coating for corrosion resistance and long-lasting performance.
• About The Axle U-bolt Kit: This kit include 4 x 7" long U bolts, U-bolt thread diameter is 1/2",the curvature (inside diameter) of the U-bolt is 3 1/9"; 2 x tie plates for 1-3/4" or 2" leaf springs; 8 x 1/2"-20 hex nuts. And this kit used for 3" dia round trailer axle.(This product offer 2* U-bolt kit).
• About The Trailer Axle Hanger Kit: This kit include 2 x EQ-E1 equalizers, 6 x 3" tall hangers, 8 x shackle straps, 14 x 9/16"-18 x 3" long shackle bolts and locknuts. And this kit used for 1-3/4" leaf springs.
• After-sales service: Any questions after receiving, please contact us freely. Thanks for choosing us!

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RV MURTS 4 Leaf Trailer Spring Kit – Corrosion-Resistant Set

The RV MURTS 4 Leaf kit is tailored for 3,500lb single axle or tandem suspension, with each spring offering 1,750lbs capacity. The double-eye springs measure 25-1/4 inches eye-to-eye, with a 3-inch free open and 1-3/4-inch width. The four-leaf design uses prominent steel with an anti-corrosion coating, making it suitable for boat trailers exposed to moisture. The kit includes four 5-1/2-inch U-bolts, two tie plates, eight hex nuts, four hangers, eight shackle straps, and necessary lock hardware.

This kit is particularly useful for cargo or boat trailers where corrosion resistance is key. The included shackle kit allows for easy installation and adjustment. While it’s designed for 3,500lb axles, the complete hardware set means you won’t need to buy extra parts. If you’re looking for a durable, all-in-one suspension solution for your boat or utility trailer, the RV MURTS kit is a practical choice.

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• Compatibility. 4 leaf springs kit with U-bolt, hanger and shackle kit for 3,500lb trailer axle tandem suspension, each double eyes single leaf spring offers 1,750lbs capacity impressive shock absorbent for cargo, boat trailer, heavy duty and durable for years use.
• Trailer Leaf Spring. Check the detail in the pictures for sure fit, eye to eye length: 25-1/4 inch; free open: 3 inch; width of leaf: 1-3/4 inch; 4 leaves; 9/16 inch bushing dia, OEM reference: SW4B / 72-42 / LIB-401-DE / UNA212 / PR4B / 124903 / 9150014 / 93184.
• Includes. Tandem trailer leaf spring kit included compatible 4 U-bolts feature 5-1/2'' long, 1/2'' dia, 2 tie plates and 8 hex nuts, 4 hangers, 8 shackle straps and necessary locknuts and shackle bolts for one package easy replacement.
• Durability. Trailer axle springs constructed with prominent steel with anti-corrosion coating, DOT qualified hardware and accessories improve the suspension system for long time and long distance journey in years.
• Stability. Not only provide stable driving experience with dynamic shock absorption on potholed road when heavy loads, heavy duty trailer leaf spring kit also stay intact in commercial vehicles.

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Youxmoto 4-Pack 5 Leaf Springs – Multi-Spring Heavy-Duty Kit

The Youxmoto kit includes four 5-leaf springs, each with 3,000lbs capacity, designed for 5,200-6,000lb tandem trailer axles. The springs measure 25-1/4 inches long, 1-3/4 inches wide, with a 9/16-inch bushing diameter. This kit replaces SW5 springs and includes a U-bolt set for 3-inch diameter round axles, with four 7-inch U-bolts, two tie plates, and a full hanger kit with equalizers, hangers, and shackle straps. The springs are made from durable materials for long-lasting performance.

Installation requires attention to detail: the nut must be tightened horizontally to avoid affecting use. The four-spring pack is ideal for trailers needing extra support, such as those carrying heavy equipment. With all necessary hardware included, this kit simplifies the upgrade process. If you need a multi-spring solution for a heavy-duty trailer, the Youxmoto kit offers excellent value and comprehensive coverage.

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• Youxmoto 4pcs 5 Leaf Springs 3000lb, for 5200lb-6000lb Tandem Trailer Axle Suspension Kit
• DIRECT REPLACEMENT: Replace For SW5. Attention: The nut must be tightened horizontally, otherwise it will affect its use
• COMPLETE ACCESSORIES: Include 5,200-6000lbs axle U-bolt kit for 3" dia round trailer axle, Kit include: 4 x 7" long U bolts; U bolts dia. 1/2"; 2 x tie plates for 1-3/4" or 2" leaf springs; 8 x 1/2"-20 hex nuts.
• EASY INSTALLATION: Include Complete tandem trailer axle hanger kit for 1-3/4" leaf springs, Kit include: 2 x EQ-E1 equalizers; 6 x 3" tall hangers; 8 x shackle straps; 14 x 9/16"-18 x 3" long shackle bolts and locknuts.
• WHY CHOOSE Youxmoto: 5-leaf design, Leaf Springs Made of Heavy Duty Carbon Steel for transmission stability; Extra added anti-rust coating for corrosion resistance and long-lasting performance.

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Buyer’s Guide: What to Consider

Consider your trailer’s axle capacity, spring length, and included hardware to ensure a perfect fit and safe towing.

• Load Capacity: Match the spring's capacity to your trailer's axle rating. For 3,500lb axles, use 1,750lb springs; for 5,200-6,000lb axles, use 3,000lb springs.
• Spring Length: Standard eye-to-eye length is 25-1/4 inches. Measure your old spring's length to confirm compatibility with your trailer's suspension setup.
• Included Hardware: Most kits include U-bolts, tie plates, hangers, and shackles. Ensure the U-bolt diameter and curvature match your axle tube size (round or square).
• Material & Coating: Springs with anti-rust coatings or carbon steel construction resist corrosion and provide stable damping over time, especially in wet conditions.
• Replacement Part Number: Check if the kit replaces common part numbers like SW4B or SW5. This simplifies finding a direct fit for your trailer model.

Conclusion

Choosing the right trailer leaf spring kit comes down to matching your axle’s capacity and ensuring the hardware fits your trailer’s suspension. For 3,500lb axles, the SEHNSUCHT 4 Leaf kit offers a complete, durable solution, while the AEagle kit provides a reliable alternative with anti-rust coating. For heavier 5,200-6,000lb axles, the SEHNSUCHT 5 Leaf and Youxmoto kits deliver the extra strength you need.

If you’re looking for a well-rounded kit with all necessary components, the RV MURTS 4 Leaf kit is a solid choice for boat or cargo trailers. Always double-check your spring length and U-bolt dimensions before purchasing to ensure a smooth installation and safe towing.