A U-bolt that is the wrong width or too short will not clamp the spring to the axle properly. Measure these four things before you order.
1. Diameter (thread size)
Measure across the threaded rod: common sizes are 3/8", 7/16", 1/2", 9/16", 5/8", 3/4", 7/8" and 1". Note the thread pitch if you know it (for example 5/8"-18).
2. Bend shape
Round bend fits round axle tubes. Square bend fits square axles, spring perches and many heavy truck applications. Semi-round is also available for some trucks.
3. Inside width
Measure the inside distance between the two legs. For a round U-bolt this should match the axle tube diameter; for square bend, the width of the axle or seat.
4. Inside length
Measure from the inside of the bend to the end of the thread. Allow enough length to pass through the spring pack, any lift block, the plate and a full nut with at least two threads showing.
Install tips
- Use new U-bolts and nuts whenever springs are replaced; stretched U-bolts should not be reused.
- Tighten in a cross pattern to the vehicle or spring manufacturer's torque spec, and re-check after the first few hundred kilometres.
Shop U-bolts by size, U-bolt plates and trailer axle U-bolt kits, or send your measurements through our contact page and we will match them.
Replacing springs too? See how to measure a leaf spring for replacement.