Isayokgo 3/8" x 4" Leaf Spring Center Bolts — 4pc Set with Lock Nuts, Fine Thread for Trucks/SUVs/Trailers

These Isayokgo 3/8" x 4" fine-thread leaf spring center bolts (4 pieces with lock nuts) are a universal, ready-to-install replacement set for aligning and clamping leaf spring packs on trucks, SUVs, and trailers.

When servicing or rebuilding a multi-leaf spring pack, the center bolt secures the leaves and keeps the assembly aligned under load. The Isayokgo set includes four 3/8" diameter by 4" long bolts with fine threads and accompanying lock nuts so you can replace a worn or missing center bolt quickly. Their cut-to-length design allows trimming excess thread after installation for a neat fit, while the supplied nuts let you complete the job without hunting for fasteners.

How will these bolts fit my vehicle's leaf spring pack?

These center bolts are designed for universal compatibility where a 3/8" center bolt and up to 4" pack thickness are specified. Measure the existing hole diameter and the total packed leaf thickness to confirm fit before ordering. If you have an uncommon or hardened center bolt requirement, verify with your vehicle manufacturer or shop.

• Bolt diameter: 3/8" (0.375")
• Bolt length: 4" overall (fine-thread majority)
• Suitable for packs ≤ 4" thick after compression
• Common fit for many trucks, SUVs and light trailers — always confirm measurements

Are these bolts strong enough for routine leaf-pack service?

They are intended for general service and routine leaf-pack maintenance such as adding or removing leaves and re-assembly. Listings note these bolts are not necessarily hardened or graded for extreme heavy-duty builds; for high-load or performance spring packs, choose a hardened, grade-specified bolt. For routine repairs and roadside replacements, these provide a safe, convenient option when used with proper clamps and torque practices.

• Good for routine maintenance and replacing worn center bolts
• Not recommended for custom heavy-duty performance springs without upgrade
• Use C-clamps and correct torqueing to avoid over-stress
• Trim excess thread after tightening for a clean installation

What installation steps give the most reliable result?

Clamp the leaf pack securely with C-clamps to maintain alignment while you insert and tighten the center bolt. Snug the nut until leaves are compressed, then trim any protruding thread and install the lock nut to prevent loosening. Avoid using excessive torque since these bolts may not be heat-treated; for repeat or high-stress applications, replace with graded hardware.

• Compress and align pack with C-clamps before inserting bolt
• Tighten nut until leaves seat, then trim excess bolt length
• Install supplied lock nut to resist vibration loosening
• Choose hardened bolts if specification or heavy use requires it

How many pieces and hardware are included in the kit?

The Isayokgo kit contains four 3/8" x 4" fine-thread center bolts plus matching lock nuts, providing a full set for multiple leaf packs or future spares. That makes the set practical for servicing both axles on many light trucks and trailers without sourcing additional nuts.

• 4 center bolts (3/8" x 4")
• 4 matching lock nuts for secure fastening
• Ready-to-install — no separate nuts required
• Cut-to-length threads for tidy final assembly

Who is this for: This Isayokgo set is aimed at mechanics, DIYers, fleet maintenance workers, and trailer owners who need a straightforward, economical center-bolt replacement for common leaf spring packs. If you perform routine leaf spring repairs, want spare hardware for roadside fixes, or are rebuilding stock springs, these bolts and lock nuts offer a practical, easy-to-use option — just confirm hole diameter and pack thickness, and choose hardened bolts if your application demands higher strength.