Leaf Spring Bolt with Fitting Position Rear

Nolathane leaf spring bolts are universal leaf spring U-bolt kits that clamp the leaf spring pack to the axle. They aren?t eye, shackle or center bolts. These axle U-bolts suit trucks, pickups and 4x4s with leaf spring suspension, whether you?re replacing springs, fitting lift blocks, or fixing an axle that has shifted on its springs.

Each U-bolt kit is sized for a specific spring and axle combination, so getting the measurements right comes first. Each listing shows the inside width, length, thread and bend.

The Four Jobs of a Leaf Spring U-Bolt

U bolts for truck and 4x4 leaf suspension do more than hold parts together. They have four jobs:

• Clamp the spring pack. The U-bolts squeeze the leaves tightly together, so the pack works as one unit.
• Locate the axle. The clamp holds the axle in its position on the spring, keeping wheelbase and alignment where they should be.
• Stop flex at the center. A tight clamp keeps the section around the center bolt from flexing. When that section is allowed to flex, leaves crack and the center bolt can shear.
• Hold blocks and spacers. Where a lift block or spacer sits between the spring and the axle, the U-bolts keep the whole stack locked together.

When the clamp load drops, all four jobs suffer at once.

How to Measure Leaf Spring U-Bolts

Measuring accurately is the most important step with universal leaf spring U-bolts. Each listing shows the inside width, length, thread and bend, and the U-bolts are guaranteed to match the dimensions shown in the listing.

Bend Type

The bend is the shape at the top of the U. It must match the shape of the axle tube or axle seat it wraps around.

• Square bend: Square U-bolts have a flat top with sharp corners, for square axle seats and housings.
• Round bend: Round U-bolts curve fully, to wrap a round axle tube.
• Semi-round bend: A semi-round bend has a curved top with straight sides, for round axles where the legs need to run straight down past the spring.

Rod or Thread Diameter

Rod diameter is the thickness of the U-bolt?s legs, and thread size is the diameter and pitch of the threads. Diameter has a big effect on clamp load. A thicker rod can be tightened to a higher clamp force, so match the rod diameter to the original or the vehicle?s specification. Each listing shows the thread size.

Inside Width Between the Legs

Measure the inside width between the two legs. That?s the width of the spring or axle seat the U-bolt has to fit around. Too wide, and the spring can shift. Too narrow, and the U-bolt won?t fit.

Leg Length

Measure leg length from the inside of the bend to the end of the thread. The legs need to pass through the spring plate with enough thread left to fit a full nut. If you?re adding a lift block, add its height to the length you need.

US buyers often measure in inches, but the listings use metric sizes, so convert your measurements carefully before ordering.

What a U-Bolt Kit Includes

A leaf spring bolt kit includes the U-bolts, nuts and washers needed for the installation, and each listing shows the kit contents.

Fresh nuts and washers matter as much as the U-bolts themselves. Nuts that have been torqued before can have stretched or damaged threads, and old washers may be dished or worn. Fitting a complete new kit makes sure every part of the clamp can reach the right clamp load.

Grade, Strength and Load

The U-bolt?s material and grade must suit the vehicle?s weight, its payload, and any towing it does. Heavier loads put more stress on the clamp.

A U-bolt that isn?t strong enough can stretch under load. Once it stretches, it loses clamp load, the spring pack loosens, and the axle can shift. Check the grade and suitability for your vehicle and use before you order, and talk to our support team if you?re not sure.

U-Bolts With Lift Blocks and New Springs

Fitting lift blocks raises the stack between the spring and the axle, so the original U-bolts are usually too short. You?ll need longer legs to clear the block and still leave a full nut?s worth of thread.

When you fit new leaf springs, fit new U-bolts with them. While everything is apart, check the condition of the spring plate (or U-bolt plate) and the axle seat. Bent, cracked or rusted plates and seats can?t hold the clamp evenly.

Why New U-Bolts Every Time

Once a U-bolt has been torqued, it has stretched slightly, so it can?t reach the same clamp load again. Its threads can be damaged on removal, and a U-bolt that has spent years under load may be fatigued.

For that reason, replace the U-bolts whenever they?ve been removed, rather than refitting the old ones.

Torquing Leaf Spring U-Bolts

Torque is where most U-bolt problems start. Follow your vehicle?s leaf spring U-bolt torque specs rather than general figures.

• Use a cross pattern. Run the nuts down evenly, then torque them in a diagonal, cross-pattern sequence.
• Torque in stages. Bring all the nuts to partial torque in that pattern first, then to full torque in the same pattern.
• Load the axle where specified. Some specifications call for final torque with the vehicle?s weight on the axle.
• Re-torque. Check the torque again after the first few miles of driving, and again after heavy loads or towing.

U-bolts are safety-critical, so qualified fitting is recommended.

Limitations and Trade-Offs

• Universal U-bolts depend on accurate measuring
• The listings use metric sizes
• New U-bolts can?t fix a cracked spring, a broken center bolt, damaged spring plates or a worn axle seat
• Confirm the grade and load suitability before towing or heavy hauling

Compliance and Insurance

Follow the inspection and towing rules of the state where the vehicle is registered, including trailer rules where they apply. Tell your insurance company about any modifications, such as lift blocks.

Warranty and Support

Nolathane leaf spring bolts are backed by Nolathane?s warranty. If you need help measuring your U-bolts, our local support team can help.

Shop Leaf Spring U-Bolts

U-bolt kits are listed in our nuts, bolts and screws selection, and leaf spring pads stop the spring creaking on the axle seat.

Find leaf spring U-bolt kits for your truck, pickup or 4x4, and order online with fast shipping on in-stock sizes. Every kit is covered by our fitment guarantee to match the dimensions shown in the listing.