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Recommended U-Bolt Torque Chart
Maximum Torque Values – Plated vs. Unplated
Important: These torque values are general guidelines for cold-formed U-bolts.
Always follow OEM service manual specifications when available.
| U-Bolt Size | Material Grade | Max Torque (ft-lbs) – Plated | Max Torque (ft-lbs) – Unplated |
|---|---|---|---|
| 3/8″-24 | Grade 5 | 21 | 26 |
| 7/16″-20 | Grade 5 | 33 | 44 |
| 1/2″-20 | Grade 5 | 52 | 70 |
| 1/2″-20 | Grade 8 | 64 | 87 |
| 9/16″-18 | Grade 5 | 107 | 143 |
| 9/16″-18 | Grade 8 | 93 | 124 |
| 5/8″-18 | Grade 5 | 107 | 143 |
| 5/8″-18 | Grade 8 | 132 | 177 |
| 3/4″-16 | Grade 5 | 190 | 253 |
| 3/4″-16 | Grade 8 | 234 | 313 |
| 7/8″-14 | Grade 5 | 304 | 405 |
| 7/8″-14 | Grade 8 | 375 | 500 |
| 1″-14 | Grade 8 | 758 | 1,010 |
| 1-1/8″-12 | Grade 8 | 848 | 1,131 |
| 1-1/4″-12 | Grade 8 | 1,163 | 1,551 |
Important Torque Notes
- Torque values assume clean, dry threads
- Anti-seize lubrication will reduce required torque
- Lubricated U-bolts typically torque between plated and unplated values
- All torque values are initial install values only
Re-Torque Requirement (Critical)
Cold-formed U-bolts stretch slightly after initial torque.
ATS Springs recommends:
- Initial torque at installation
- Drive vehicle under normal load
- Re-check and re-torque after 50–100 miles
Failure to re-torque can result in:
- Loss of clamping force
- Axle movement
- Premature U-bolt fatigue or failure
Proper U-Bolt Tightening Sequence
Always tighten U-bolts using a cross-pattern sequence:
- Snug all nuts evenly
- Torque in stages (do not fully torque one side first)
- Final torque using the same cross pattern
This ensures even load distribution across the axle seat and leaf spring pack.
Why ATS Recommends New U-Bolts Every Time
- U-bolts permanently stretch when torqued
- Reused U-bolts cannot maintain proper preload
- Old U-bolts increase the risk of loosening and failure
Reusing old U-bolts is not recommended under any circumstance.
Maximum Torque Values – Plated vs. Unplated
