Common Trailer Torque Guide
The following torque settings are a general guide only for common trailer applications. Always check the axle, hub, wheel, brake and suspension manufacturer’s specifications before final assembly.
Torque values can vary depending on thread size, thread pitch, nut type, bolt grade, coating, lubrication and whether the fastener is new or reused.
General Rules
- Always use a calibrated torque wrench for final tightening.
- Do not use a rattle gun for final torque.
- Start all nuts by hand to avoid cross-threading.
- Tighten wheel nuts in a criss-cross/star pattern.
- Re-check wheel nuts after first use, after wheel removal and again after a short road test.
- Do not over-tighten castle nuts. The hub must rotate freely with no excessive end play.
- Replace damaged, stretched, rusty or worn fasteners.
- If using nyloc nuts, make sure at least three full threads are visible past the nut once tightened.
Wheel Nut Torque Guide
| U-Bolt Size | Torque ft/lb | Torque Nm |
|---|---|---|
| 1/2″ UNF / M12 | 90–110 ft/lb | 120–150 Nm |
| 5/8″ UNC/UNF / M16 | 110–150 ft/lb | 150–200 Nm |
Wheel Nut Notes
For many light trailer wheels, 1/2″ wheel nuts are often torqued around 90 ft/lb / 120 Nm. Some larger Dexter-style 14″, 15″ and 16″ wheel applications list 1/2″-20 wheel nuts at 100–120 ft/lb, so always check the wheel and axle supplier’s requirement.
Wheel nuts should be checked:
- Before first road use
- After wheel removal
- After the first short drive
- Periodically during service
Hub Castle Nut Guide
| Component | Torque / Adjustment Guide |
| Hub castle nut | Tighten while rotating the hub to seat the bearings, then back off and re-tighten by hand until snug |
| Final setting | Hub should spin freely with no excessive side-to-side play |
| Split pin | Fit through the nearest slot without over-tightening the nut |
Castle Nut Notes
A castle nut is not normally tightened to a final high torque like a wheel nut. It is used to correctly set wheel bearing preload/end float.
General method:
- Tighten the castle nut while rotating the hub to seat the bearings.
- Back the nut off.
- Re-tighten by hand or lightly with a spanner until just snug.
- Back off slightly if needed to align the split pin.
- Fit a new split pin.
- Check that the hub spins freely and there is no excessive movement.
Do not preload trailer taper roller bearings too tightly, as this can cause heat build-up and premature bearing failure.
Brake Backing Plate / Brake Mounting Nut Torque
| Brake / Fastener Type | Torque ft/lb | Torque Nm |
|---|---|---|
| 3/8″ backing plate bolt | 30–35 ft/lb | 40–47 Nm |
| 7/16″ backing plate bolt | 45–60 ft/lb | 60–80 Nm |
Backing Plate Notes
Brake backing plate nuts should be tightened evenly and checked after installation. Loose backing plate hardware can cause brake misalignment, poor braking performance or brake damage.
Use the correct nuts, washers and mounting hardware for the brake assembly.
U-Bolt Torque Guide
| U-Bolt Size | Common Use | Torque Guide |
| 1/2″ UNF | Common trailer axle U-bolts | 90–110 ft/lb / 120–150 Nm |
| 5/8″ UNC/UNF | Heavy-duty trailer U-bolts | 110–150 ft/lb / 150–200 Nm |
U-Bolt Notes
U-bolts clamp the axle, spring and tie plate together. Correct torque is important because loose U-bolts can allow axle movement, spring damage or suspension misalignment.
General method:
- Tighten U-bolt nuts evenly in stages.
- Alternate between nuts so the plate pulls down square.
- Do not fully tighten one side before the other.
- Re-check after initial use, as the spring pack and hardware can settle.
- Replace U-bolts if they are stretched, damaged, heavily corroded or have been overloaded.
U-bolt torque can vary depending on whether the nut is a standard hex nut, flange nut or serrated flange nut.
Common Trailer Bolt / Nut Guide
| Fastener Size | Torque ft/lb | Torque Nm |
|---|---|---|
| M8 Grade 8.8 | 18 ft/lb | 25 Nm |
| M10 Grade 8.8 | 45 ft/lb | 60 Nm |
| M12 Grade 8.8 | 75 ft/lb | 100 Nm |
| M12 Grade 10.9 | 90 ft/lb | 120 Nm |
| 1/2″ Grade 5 / 8 | Check component supplier specification | Check component supplier specification |
| 5/8″ Grade 5 / 8 | Check component supplier specification | Check component supplier specification |
Important Safety Note
This guide is intended as a general reference for common trailer servicing. The correct torque must always be confirmed against the specific axle, wheel, brake, coupling or suspension manufacturer’s specification.
If unsure, contact Manutec before assembly.