Replace a Floating Caliper Without Losing Installation Control
- Maintain safe support and hydraulic isolation during removal.
- Control caliper orientation, rotor retention, and fastener installation.
- Complete hydraulic service using the actuator documentation.
- Floor jack, jack stands, and wheel chocks — Lift and securely support the trailer while preventing unintended movement.
- Socket set and ratchet — Remove the wheel and caliper mounting bolts and install temporary rotor-retaining lug nuts.
- Torque wrench — Tighten mounting bolts, the hose connection, and wheel fasteners to their applicable specifications.
- Hydraulic fitting wrenches — Disconnect and reconnect the hose while controlling the mating fitting and avoiding rounded flats.
- Caliper support hook — Support the caliper during removal so its weight does not load the hose.
- Brake bleeding hose and catch container — Collect discharged fluid during bleeding and flushing as directed by the actuator manual.
The covered small floating-caliper procedure starts with safe support, wheel removal, actuation disabled, no hydraulic pressure, and free hub-and-rotor rotation. Caliper replacement requires disconnecting the hose; the caliper must still be supported rather than allowed to hang from it.
Inspect the brake assembly before fitting the replacement. The new caliper is installed with its bleed screw pointing upward. Temporary lug nuts hold the rotor against the hub during caliper assembly and are removed afterward.
The new mounting bolts require thread-locking compound. Dexter specifies 40–50 ft-lb for the mounting bolts and 10–12 ft-lb for the hose connection to the elbow adapter on the covered 3.5K assembly. These are application-specific values and vary by maker.
After reconnecting the hose, reconnect actuation and bleed and flush according to the actuation-system manual. The supplied pages refer that detailed hydraulic procedure to the actuator documentation; they do not provide a universal bleeding order. Finish by mounting the wheel using its applicable wheel-fastener procedure.
How It Works
Control the assembly before opening the hydraulics
Begin with safe trailer support, wheel removal, disabled actuation, no hydraulic pressure, and verified free hub-and-rotor rotation. Support the caliper while disconnecting the hose and removing the mounting bolts; hanging weight can strain the hose and its connections. Inspect the rotor and mounting hardware before fitting the replacement, and replace unacceptable components.
Orientation and retention determine installation quality
Install the replacement with its bleed screw pointing upward because trapped air rises and must reach the bleed outlet. Use 2 lug nuts to hold the rotor against the hub during assembly, then remove them after caliper assembly. Apply thread-locking compound to the new mounting bolts and, for the covered Dexter 3.5K assembly, tighten them to 40–50 ft-lb; these values vary by maker.
Mechanical installation is not hydraulic completion
For the covered Dexter 3.5K assembly, tighten the hose connection to the elbow adapter to 10–12 ft-lb rather than using the mounting-bolt torque. After reconnecting the hose, reconnect actuation and bleed and flush under the actuator manual: air compresses under pressure and can delay or weaken braking response. The supplied procedure gives no universal bleeding order; finish by mounting the wheel using its applicable wheel-fastener procedure.
Step-by-Step Procedure
0/7 doneDexter 3.5K caliper installation values; values vary by maker
| Caliper mounting bolts | 40–50 ft-lb |
| Hose connection to elbow adapter | 10–12 ft-lb |
| Temporary rotor retention during assembly | 2 lug nuts; remove after caliper assembly |
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Hub and rotor do not rotate freely before removal. | Confirm actuation is disabled and hydraulic pressure is absent; inspect the brake assembly before proceeding. | Verify no hydraulic pressure and free hub-and-rotor rotation before removal. | Remaining hydraulic application or mechanical binding may be preventing free rotation. Basis: LDServiceOnline |
| Air remains difficult to clear after caliper replacement. | Inspect bleeder orientation and confirm bleeding and flushing follow the actuator manual. | Bleed screw pointing upward; bleed and flush according to the actuation-system manual. | Incorrect caliper orientation can trap air away from the bleed outlet; an incomplete hydraulic procedure can leave air in the system. Basis: LDServiceOnline |
| Mounting-bolt installation cannot be verified. | Confirm the application, new mounting bolts, thread-locking compound, and documented torque before accepting the installation. | Covered Dexter 3.5K mounting bolts: 40–50 ft-lb with thread-locking compound; values vary by maker. | Omitted thread-locking compound or an unverified tightening procedure leaves fastener retention uncertain. Basis: LDServiceOnline |
| Fluid appears at the hose-to-elbow connection after reconnection. | With actuation disabled and pressure absent, inspect the connection for damage or incorrect seating and verify the application-specific torque. | Covered Dexter 3.5K hose connection to elbow adapter: 10–12 ft-lb; values vary by maker. | Incorrect seating, damaged mating parts, or improper tightening may prevent the connection from sealing. Basis: LDServiceOnline |
At the Bay: Diagnose the Case
CASE 1 / 4
Hub and rotor do not rotate freely before removal.
- Test
- Compare
- Correct
Select the next check
Basis: LDServiceOnline. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Letting the caliper hang from its hose during removal.
- ✕ Installing the bleeder downward or forgetting temporary lug-nut removal.
- ✕ Omitting thread-locking compound or treating Dexter torque values as universal.
- ✕ Skipping bleeding and flushing or inventing a bleeding order.
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
Hydraulic Pressure & Relief Gauge
0–5,000 psi gauge on the pump pressure port, DC clamp meter, battery voltmeter
🛠 Equip your bay for this test →Symptom: Routine check before a customer pickup.
Spec limits used
- 3,200 psi — Primary relief (factory preset) (KTI Hydraulics Troubleshooting Manual 2019)
- 1,500 psi — Secondary relief, circuit 111 (KTI Hydraulics Troubleshooting Manual 2019)
- below 9 V — Low-voltage alarm (KTI remote)
- illustrative only — Motor current & voltage drop (General shop practice)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Source: LDServiceOnline — 34-35