Free U-Bolt Torque Chart - Grade 5 & Grade 8
Download a print-ready U-bolt torque guide for cold-formed U-bolts. Covers Grade 5 and Grade 8 hardware from 3/8 inch to 1-1/4 inch with maximum torque values in ft-lbs. Built for heavy-duty repair shops by ShopView.
U-Bolt Torque Specs for Every Bay
Suspension work is unforgiving when torque specs are wrong. This chart covers cold-formed U-bolts in Grade 5 and Grade 8 from 3/8" through 1-1/4", with maximum torque values in ft-lbs. Print it out and post it where your suspension techs work.
- Grade 5 and Grade 8 cold-formed U-bolts
- 3/8" through 1-1/4" sizes covered
- Round, square, and semi-round bolt diagrams
- Print-ready 300 DPI high-resolution PNG
- 4" x 7" magnet / sticker size
Important: Never re-use U-bolts. Always replace with new hardware.
U-Bolt Torque Specs for Suspension and Leaf Spring Work
Getting U-bolt torque right is critical for axle alignment, ride quality, and safety. Under-torqued U-bolts allow the axle to shift under the leaf spring pack, causing alignment issues and uneven tire wear. Over-torqued U-bolts can crack the spring center bolt hole or distort the spring seat. Either way, you've got a truck coming back to the shop.
This chart covers cold-formed U-bolts, which are the standard type used in most heavy-duty leaf spring applications on Class 5 through Class 8 trucks. Cold-formed U-bolts are bent at room temperature and are stronger than hot-formed U-bolts, which are heated before bending. Do not use hot-formed U-bolt torque values interchangeably with cold-formed values — they are different.
U-bolts should never be re-used. Once a U-bolt has been torqued, it permanently stretches. Reusing a stretched U-bolt means it won't achieve the same clamping force, even at the same torque value. Always install new U-bolts during leaf spring replacement, re-pack jobs, or any suspension work that requires removing them.
For grade selection: Grade 5 U-bolts are adequate for most light and medium-duty applications, while Grade 8 U-bolts are recommended for heavy-duty and vocational trucks that see high loads, rough terrain, or heavy payloads. Plated U-bolts (zinc or cadmium) will have lower friction on the threads, which means the same torque value produces higher clamping force — so plated bolts may require adjusted torque values per the OEM manual.
U-Bolt Torque Quick Reference
Maximum torque values in ft-lbs for unplated cold-formed U-bolts. For use in leaf spring and suspension applications on heavy-duty trucks. Always refer to the OEM service manual when available.
| Size | Material Grade | Max. Torque (ft-lbs) |
|---|---|---|
| 3/8 - 24 | Grade 5 | 26 |
| 7/16 - 20 | Grade 5 | 44 |
| 1/2 - 20 | Grade 5 | 70 |
| 1/2 - 20 | Grade 8 | 87 |
| 9/16 - 18 | Grade 5 | 100 |
| 9/16 - 18 | Grade 8 | 124 |
| 5/8 - 18 | Grade 5 | 143 |
| 5/8 - 18 | Grade 8 | 177 |
| 3/4 - 16 | Grade 5 | 253 |
| 3/4 - 16 | Grade 8 | 313 |
| 7/8 - 14 | Grade 5 | 405 |
| 7/8 - 14 | Grade 8 | 500 |
| 1 - 14 | Grade 8 | 1010 |
| 1-1/8 - 12 | Grade 8 | 1131 |
| 1-1/4 - 12 | Grade 8 | 1551 |
All values are general guidelines for unplated cold-formed U-bolts. The OEM service manual on specific models always takes precedence over values shown.
Frequently Asked Questions
Why should you never re-use U-bolts?
U-bolts permanently stretch when torqued to specification. Once stretched, the bolt cannot achieve the same clamping force even if torqued to the same value again. Reusing a stretched U-bolt risks the axle shifting under the leaf spring pack, leading to alignment problems, uneven tire wear, and potentially dangerous handling. Always install new U-bolts during any suspension work that requires their removal.
What is the torque spec for a 3/4 inch U-bolt?
For a 3/4 - 16 cold-formed U-bolt, the maximum torque is 253 ft-lbs for Grade 5 and 313 ft-lbs for Grade 8. These values are for unplated hardware with clean, dry threads. Plated U-bolts may require different torque values — check the OEM service manual.
What is the difference between cold-formed and hot-formed U-bolts?
Cold-formed U-bolts are bent at room temperature, which work-hardens the steel and makes them stronger. Hot-formed U-bolts are heated before bending, which makes the bend easier but results in lower strength at the bend point. Cold-formed U-bolts are the standard for most heavy-duty truck leaf spring applications. The torque values in this chart are specifically for cold-formed U-bolts — do not use them for hot-formed hardware.
Should I use Grade 5 or Grade 8 U-bolts on my truck?
Grade 5 U-bolts are suitable for most standard-duty applications. Grade 8 U-bolts are recommended for heavy-duty and vocational trucks (Class 6–8), trucks that carry heavy payloads, or vehicles that operate on rough terrain where suspension components see higher stress. Always match the grade specified by the truck manufacturer or spring supplier. When in doubt, use Grade 8 — you can always go stronger, but never weaker.
Do I need to re-torque U-bolts after installation?
Yes. New U-bolts should be re-torqued after 500 to 1,000 miles of driving. The leaf spring pack settles under load, and the U-bolts will lose some clamping force as the components seat. Failing to re-torque can result in loose U-bolts, axle movement, and premature wear on the spring pack and bushings.
Are these torque values different for plated U-bolts?
Yes, they can be. Plated U-bolts (zinc, cadmium, or other coatings) have lower thread friction than unplated bolts. Lower friction means the same torque value produces higher clamping force, which can over-stress the bolt or the spring components. The values in this chart are for unplated cold-formed U-bolts. If you're using plated hardware, check the manufacturer's specifications for adjusted torque values.
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