Electric Brake Adjustment
- Perform manual starwheel adjustments to ensure uniform shoe expansion.
- Schedule recurring brake service based on documented mileage intervals.
- Execute a proper brake back-off procedure to achieve the specified lining drag.
- Jack and jack stands — Lift the trailer and secure the frame to allow for free wheel rotation during adjustment.
- Brake adjustment tool or flat-blade screwdriver — Rotate the starwheel through the backing plate access hole to expand or retract brake shoes.
- Small pry tool or wire — Hold the auto-adjust lever away from the starwheel during the back-off procedure.
- Adjusting-hole cover — Protective plug removed to access the starwheel and replaced after service to keep debris out.
Adjust brakes manually after the first 200 miles and about every 3,000 miles after that.
How It Works
Initial and Recurring Service Intervals
Brake components require an initial seating period and regular maintenance to compensate for lining wear. Manual adjustments must be performed after the first 200 miles of operation. Following this break-in period, the interval for adjustment is approximately every 3,000 miles.
The Expansion and Back-Off Method
Correct shoe-to-drum clearance is achieved by first expanding the shoes until the wheel becomes very difficult to turn. This ensures the shoes are centered and fully seated against the drum. The starwheel is then backed off until a slight lining drag is felt, providing the necessary operating clearance.
Uniformity Across Axles
Consistent braking force depends on identical adjustment across all hubs. The adjustment procedure must be repeated on all brakes so they are set the same, preventing the trailer from pulling to one side or experiencing uneven component wear.
Step-by-Step Procedure
0/6 doneDiagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Starwheel will not rotate in the retracting direction. | Attempt to move the starwheel while manually holding the auto-adjust lever away from the teeth. | Per the applicable manual | The auto-adjust lever is engaging the starwheel teeth, preventing reverse rotation. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Uneven braking force or trailer pulling to one side. | Verify that the adjustment procedure was repeated on all brakes and settings are identical. | Repeat on all brakes so they are set the same. | Individual brakes were not adjusted to the same level of lining drag. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Excessive brake heat or premature lining wear. | Review the mileage since the last adjustment and check for slight lining drag. | Adjust brakes manually after the first 200 miles and about every 3,000 miles after that. | Brakes have exceeded the 3,000-mile service interval or were not backed off sufficiently. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
At the Bay: Diagnose the Case
CASE 1 / 3
Starwheel will not rotate in the retracting direction.
- Test
- Compare
- Correct
Select the next check
Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014). A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Forgetting to perform the first manual adjustment at the 200-mile mark.
- ✕ Attempting to back off the starwheel without disengaging the auto-adjust lever.
- ✕ Adjusting only one side of the axle instead of all brakes on the trailer.
- ✕ Backing off the starwheel too far, resulting in no lining drag.
- ✕ Failing to replace the adjusting-hole cover after the procedure is complete.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Hands-on: Test Bench Practice
Symptom: Healthy trailer. Learn what good readings look like.
Tap a point to place the red probe.
Good system: ~12.6 V at pins, 3.2 Ω across a 12×2-inch magnet (unplugged), 3.0 A per magnet at 12 V full gain, and at least 10.5 V at the magnet — the chart values from the axle manuals.
Hands-on: Shop Test Equipment
IPA #9107B Electric Brake Force Meter
Plugs into the truck's 7-way socket on a 25 ft cable; simulates a trailer load and shows controller output on 10 blue LEDs
🛠 Equip your bay for this test →Symptom: Customer wants the truck checked before buying a trailer.
Spec limits used
- 1–10, each 1.0–1.5 V — Gain LEDs (IPA #9107B manual, p.5)
- 15 s — Max time holding brake pedal (IPA #9107B manual, p.4)
- set-up step 5 — Connect the 9-pin only after the engine is running (IPA #9107B manual, p.3)
- hold brake pedal during ECU detection — 2016–2017 'Trailer Connected' not shown (IPA #9107B manual, p.3)
- faulty brake control module or relay — ECU light never lights on a vehicle with a controller (IPA #9107B manual, p.5)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Source: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) — 9