Grade 5 Round U Bolts

• 3/8 Round U-Bolt Kits GRADE 5
• 7/16 Round U-Bolt Kits GRADE 5
• 1/2 Round U-Bolt Kits GRADE 5
• 9/16 Round U-Bolt Kits GRADE 5

Understanding Leaf Spring U-Bolts

U-bolts play a critical role in any leaf spring suspension system. Their primary function is to secure the axle firmly to the leaf spring pack, maintaining proper alignment, ride height, and handling under load.

When properly sized and torqued, U-bolts keep the axle from shifting during acceleration, braking, and cornering. When worn, stretched, or improperly installed, they can lead to axle movement, uneven tire wear, vibration, and suspension failure.

Why U-Bolts Should Always Be Replaced

U-bolts are a torque-to-yield fastener. Once torqued during installation, the steel stretches slightly to create clamping force.

Reusing old U-bolts is not recommended because:

• The metal has already stretched
• Proper torque cannot be achieved again
• Clamping force is reduced
• Risk of loosening or breakage increases over time

For this reason, new U-bolts should always be installed when replacing leaf springs, axle seats, or suspension components.

U-Bolt Bends Explained

ATS Springs supplies U-bolts in multiple bend styles to match factory and custom applications:

• Round Bend – Common on light and medium duty truck axles
• Square Bend – Often used on front axles and older applications
• Semi-Round Bend – Used where axle tubes have a flatter profile

Choosing the correct bend ensures proper fitment and even clamping pressure.

U-Bolt Materials & Strength

U-bolts are available in different strength grades depending on application:

• Grade 5 – Suitable for many standard-duty suspension applications
• Grade 8 – Higher tensile strength for heavy-duty, commercial, and high-load applications

Using the correct grade is critical for safety and long-term suspension performance.

Proper Measurement Matters

Correct U-bolt sizing is essential. Measurements include:

• Rod diameter
• Inside width between legs
• Usable thread length / leg length

ATS Springs offers sizing guidance and charts to help ensure the correct fit for your application.

Bent In-House at ATS Springs

All U-bolts are:

• Bent from straight rods
• Manufactured per order
• Designed to match your specific suspension setup

Because of this, U-bolts are considered special order items and non-returnable.

Need Help Choosing the Right U-Bolt?

If you’re unsure which U-bolt you need:

• Contact us and “Just Ask Bob”
• Or call our suspension specialists for assistance

We’ll help you select the correct size, bend, and grade for your leaf spring installation.