Kales Semi-Trailer Maintenance Guide: 9 Key Steps To Extend Lifespan & Ensure Safety

Why Regular Kales Semi-Trailer Maintenance Matters

To ensure your Kales semi-trailer operates safely, reliably, and cost-effectively, scientific and scheduled maintenance is essential. This comprehensive guide provides transport companies and fleet owners with a practical, step-by-step maintenance plan—from daily inspections to in-depth servicing—complete with a detailed maintenance schedule table to help you proactively manage vehicle condition and eliminate safety risks.

Note: For ABS (Anti-lock Braking System) inspection and repair, always refer strictly to the dedicated ABS manual.

Kales Semi-Trailer Maintenance Schedule: Daily & Periodic Inspection Checklist

Proper maintenance prevents unexpected breakdowns and extends service life. Below is the official Kales semi-trailer inspection and maintenance table, covering checks at daily, monthly, quarterly (March), and annual (December) intervals.

Semi-Trailer Daily & Periodic Inspection Table

Inspection Item	Sub-Item	Inspection Frequency				Acceptance Criteria	Notes
		Daily	Monthly	March	December
Parking Brake Valve	Braking Function	✓				Handle must engage/disengage parking brake smoothly	Inspect in parked state
Air Brake System	Air Pressure	✓				Operating pressure: 0.8–0.85 MPa
	Seal Integrity	✓				No moisture allowed in system
	Parking Brake Performance		✓			Must function normally
Hoses & Fittings	Damage/Cracks		✓			Replace if cracked or damaged	Replace hoses every 2 years Retighten fittings annually
Brake Chamber	Air Leakage	✓				No leakage permitted	Inspect under towing condition
	Condition	✓				No cracks, wear, or damage	Replace diaphragm every 2 years
	Air Build-up	✓				Should pressurize normally	Towing condition
	Pushrod Stroke		✓			Standard: 30–35 mm Max limit: 50 mm	Towing condition
Emergency Relay Valve & Air Tank
Brake Camshaft	Function	✓				Must operate normally	Towing condition
	Exhaust Sound	✓				Normal exhaust noise
	Internal Condition	✓				No water accumulation
	Wear		✓			No excessive wear or damage
Brake Drum & Lining	Clearance		✓			Auto-adjusted to 0.3–0.5 mm
Brake Lining	Wear		✓			Replace when worn to limit	Replace if rivet head is <1 mm below lining
Brake Drum	Wear		✓			Standard dia.: 420 mm Max dia.: 422 mm	Replace if over limit
Spring Brake Chamber	Function	✓				Must auto-apply when air pressure ≤ 0.4 MPa
Axle	Cracks/Deformation		✓			Replace if cracked or bent
	Axle Parallelism		✓			Check for abnormal tire wear	Adjust tie rods to align
Wheels	Tire Pressure	✓				±20 kPa from spec (per tire size)
	Cracks/Damage	✓				Replace if severe
	Tread Depth & Wear	✓				Minimum tread: 3 mm	Per wear indicators
	Foreign Objects	✓				Remove stones, metal, debris
	Lug & Hub Bolt Tightness	✓				Torque: 392 N·m
	Hub/Bearing Play		✓			Adjust if excessive play
	Oil Seal Condition		✓			Replace if aged or damaged
Leaf Spring	Broken Leaves	✓				Replace both sides symmetrically
Linkage Components	U-Bolts & Nuts	✓				Torque: 490 N·m
	Link Rod Play	✓				Replace worn rubber bushings
	Equalizer Arm Play	✓				Replace if bushing worn
	Spring Alignment	✓				No lateral shift allowed
Landing Gear	Operation		✓			Must raise/lower smoothly
	Inner/Outer Tube Damage		✓			No cracks or dents
	Mounting & Wear Points		✓			No looseness or severe wear at pivot/sliding parts
Wiring	Connection Integrity	✓				No loose or damaged connections
	Jumper Cable Condition	✓				No cuts or abrasions
Lights	Function	✓				All lights must illuminate
	Lens Condition	✓				No clouding or cracks
Turn Signals	Function	✓				Must flash correctly
Fifth Wheel Handle	Extension/Retraction		✓			Must move fully and smoothly
Kingpin	Wear/Damage		✓			50.8 mm → min 48.0 mm 89.8 mm → min 86.8 mm	Replace if below limit
Container Locks	Function				✓	Must lock/unlock reliably	Annual check
Reflectors & License Plate	Condition & Mounting	✓				Clean, undamaged, securely mounted
Chassis Frame	Cracks/Deformation	✓				Repair or realign if found
Lubrication Points	Greasing	✓				Apply grease as needed

Inspection Tips:

Perform all checks with the trailer unloaded.

When lifting, use a jack under the axle near the spring seat.

Place a steel plate or thick wood between jack and frame to prevent slippage or damage.

9 Essential Kales Semi-Trailer Maintenance Steps Explained

3.1 Brake System Maintenance: The Core of Safety

Connect the trailer’s air brake system to the tractor’s system.
Pressurize to operating level and verify pressure via tractor gauge or emergency system gauge.
With engine idling, fully depress the brake pedal and hold. Pressure drop must not exceed 50 kPa per hour.
If leakage is suspected, apply soapy water to fittings—bubbles >3 mm in 3 seconds indicate a leak. Tighten or replace as needed.
Close the tractor’s emergency shut-off valve, disconnect the emergency air line—brakes must auto-apply. If not, the emergency relay valve is faulty.

WARNING:
Never modify the brake air system—including adding water-spray brakes or tapping air from trailer tanks. This compromises braking performance and may cause catastrophic failure.

In cold weather, moisture in the brake system can freeze inside valves (relay/ABS), causing brake drag, delayed release, or total lock-up.

Daily: Drain all air tanks.

Check the tractor’s air dryer—replace desiccant cartridge if saturated.

Pushrod stroke must be 30–35 mm (max 50 mm). Left/right difference should not exceed 5 mm.
Inspect brake chambers for leaks at the exhaust port—replace diaphragm if leaking.
After replacing brake linings, reset the automatic slack adjuster:
1. Turn hex head clockwise until lining contacts drum.
2. Turn counter-clockwise ¾ turn (you’ll hear clicks).
After adjustment, wheels must rotate freely. Test drive—vehicle should not pull to one side.
Always drain air tanks after driving. Re-pressurize if excessive air loss affects brake function.

3.2 Inspect Air Lines & Fittings

Check all hoses and connectors for cracks, abrasions, or leaks. Replace immediately if damaged.

3.3 Axle & Hub Maintenance

Inspect axles and tires for bends, cracks, or damage.
Lift axle with jack (use support block).
Tighten inner hub nut to 340 N·m, then back off 1/8–1/6 turn.
Rotate hub—tap gently with a hammer near bearing. If stiff, loosen slightly until hub spins freely with no play. Install cotter pin.
Apply sealant to hub cap before installation.
Daily: Check lug nut tightness. Retorque to 600–630 N·m if loose.

3.4 Tire Care: Maximize Life & Safety

Under-inflation causes shoulder wear, ply separation, blowouts, and higher fuel consumption.
Over-inflation accelerates center tread wear and increases risk of impact damage.
Maintain correct pressure (±20 kPa) for all tires, including spares.
Rotate tires every 5,000 km to equalize wear.
Daily: Inspect lug nuts and foreign objects.

3.5 Suspension System Maintenance

Leaf Spring Suspension

Inspect springs daily for breaks. Replace both sides if one is damaged to maintain balance.
After heavy loads, retorque U-bolts to 600–650 N·m.
After new springs or first 5,000 km, inspect and retighten U-bolts monthly.
Check link rod bushings—replace if cracked or worn.

Air Suspension

Avoid long-term parking. Drive a few km periodically to cycle air springs.
After muddy or asphalt roads, clean air springs and pistons. Replace if cracked, wrinkled, or abraded.
Every 6 months:
- Inspect air dryer/filter—replace if clogged.
- Check air line seals and valve tightness.
- Verify U-bolt and air spring mounting bolt torque.
Every 3 months: Inspect shock absorbers for leaks or loose mounts.
Monthly: Check main beam bushings—no play should exist when rocking the trailer.
Every 6 months:
- Drain air tanks (every 2 weeks in freezing weather).
- Verify ride height (H-value)—must match factory specification to ensure proper coupling and stability.

3.6 Landing Gear Maintenance

Inspect for smooth operation, deformation, or damage to inner/outer tubes. Repair or replace as needed.

3.7 Kingpin & Fifth Wheel Maintenance

Inspect kingpin daily for cracks, wear, or scoring.
Replace if diameter < 48.0 mm (50#) or < 86.8 mm (90#).
Clean and inspect fifth wheel plate—remove debris, check for warping.
Lubricate kingpin and fifth wheel daily with high-quality grease (e.g., calcium-based ZG-4).

3.8 Chassis Frame Inspection

Periodically inspect frame welds and main beams for cracks or distortion. Repair immediately if found.

3.9 Axle Alignment & Wheelbase Adjustment

Misalignment causes uneven tire wear and pulling. Check if U-bolts loosen or bushings wear.

Procedure:

Park on level ground, uncouple tractor, release brakes.
Adjust landing gear so front and rear frame heights match (±2 mm).
Remove outer tires and dust caps.
Drop plumb lines from front hub inner faces to ground—mark points.
Measure from kingpin center to each point (L1, L2). Difference must be ≤ 2 mm. Adjust front/rear tie rods as needed.
Measure distance between front/rear axle points (B1, B2)—also ≤ 2 mm.
Tighten all rod nuts.
Drive 1 km, stop without braking, recheck dimensions. Repeat if needed.
Replace worn bushings or retorque U-bolts if root cause is found.

Conclusion: Professional Maintenance = Lower Costs + Higher Safety

By following this Kales semi-trailer maintenance guide, you’ll significantly extend service life, reduce unplanned downtime, and enhance road safety. Consistent, systematic care is the most effective way to protect your investment and your drivers.