Trailer Maintenance Checklist: Bearings, Brakes, Tyres, Lights, Coupling and Chains

Most trailer breakdowns and inspection failures trace back to a small, predictable list of components. None of it is complicated to check, and almost all of it is cheap to fix early and expensive to ignore. Here's what to actually go over, and how often.

Wheel bearings

Bearings are the single most common cause of a trailer being abandoned roadside, because a failed bearing tends to give little warning, then fails completely, sometimes taking the hub and wheel with it. Check for play by jacking the wheel and rocking it top to bottom; there should be no perceptible movement. Listen for grinding or humming at speed, and feel the hub for excessive heat after a drive, warm is normal, too hot to touch briefly isn't.

Bearings on a boat trailer need more frequent attention than a road-only trailer, since launching and retrieving pushes water past seals that a trailer which never touches water doesn't have to contend with; see our boat trailer guide for saltwater-specific care. As a general habit, repack or have bearings inspected at least annually on any trailer in regular use, and immediately after any trip where a hub has been submerged.

Brakes

What to check depends on what's fitted:

• Mechanical or hydraulic override brakes (common on boat trailers and lighter trailers in the 750-2000kg GTM tier): check the coupling's override mechanism moves freely and isn't seized, check the cable or hydraulic line for wear or leaks, and check the brakes actually engage when you push the coupling in by hand.
• Electric drum or disc brakes (standard above roughly 2000kg GTM): check the magnets or pads for wear, check the wiring and plug connections aren't corroded, and confirm the in-cab brake controller actually engages the trailer brakes, not just the tow vehicle's own brakes.
• The breakaway system, required above roughly 2000kg GTM: check the breakaway cable is actually attached (not just coiled up unused), and check the breakaway battery holds charge. A flat breakaway battery is one of the most common, and most avoidable, reasons a heavier trailer fails a roadworthy or safety inspection.

See our brake requirements guide for which brake type is actually required at your trailer's mass, since maintaining the wrong brake system for its GTM doesn't make it compliant.

Tyres

Trailer tyres perish with age even with plenty of tread remaining, because trailers frequently sit unused for long stretches, parked in the sun, carrying more static weight relative to their tyre size than a car does. Check for cracking in the sidewall, not just tread depth, and check the date code (most trailer tyres are five to six years old before age becomes a real concern regardless of tread). Check tyre pressure before every trip, since trailer tyres are more sensitive to under-inflation than car tyres, and check the spare, if fitted, is actually usable, not just present.

Lights and wiring

Trailer lights fail more from corroded plug connections than from blown globes. Check indicators, brake lights, tail lights and number plate light all function with a helper or a reversing camera, check the plug and socket for corrosion (a light smear of dielectric grease on the pins helps here), and check wiring along the chassis for chafing, particularly near the coupling where the cable flexes constantly.

Coupling

Whichever coupling type your trailer uses, the ball, a DO35 or similar poly-block off-road coupling, a pintle hook, a Treg coupling, or a McHitch, check it for wear at the pivot or bush, and grease it according to the manufacturer's instructions where a grease point exists. On poly-bush off-road couplings especially, the bush is a wear item that's designed to be replaced periodically rather than last the trailer's life, so if there's noticeable play or the trailer feels loose on the ball at rest, check whether it's time to replace the bush rather than assuming it's a manufacturing fault.

Check the coupling's handbrake or locking mechanism (where fitted) engages properly and the coupling can't be lifted off the ball or hitch point when locked.

Safety chains

Safety chains are the last line of defence if the coupling fails, and they need to be rated appropriately for the trailer's mass and correctly attached, generally crossed under the drawbar so that if the trailer does separate, the crossed chains help cradle the drawbar rather than letting it drop straight to the road. Check chains for wear, corrosion or stretched links, and check the attachment points on both the trailer and the tow vehicle are solid, not just present. If you're unsure whether your chains are correctly rated for your trailer's mass, a trailer parts supplier or your state's road authority can confirm the specific rating required; don't guess.

Structure and general condition

Beyond the moving parts, walk the whole trailer periodically: check the chassis and drawbar for rust or cracking, particularly around suspension mounts and any previous repair welds; check the jockey wheel operates smoothly and locks in the raised position for travel; and on a trailer with a cage, tipping mechanism or canopy, check hinges, latches and gas struts are all functioning, since these are easy to overlook until the moment you actually need one to work.

Building a routine

A reasonable baseline for a trailer in regular use: check tyres, lights and the coupling before every trip; check the brake system, including the breakaway battery, monthly or before any longer trip; and have bearings inspected at least annually, more often for a boat trailer or anything used hard. If you're hiring your trailer out between your own uses, our guide to hiring out your trailer covers keeping it in good order between hirers, and if you're buying used, our PPSR and compliance plate guide covers what to check before you own the maintenance problem in the first place.

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