Wheel bearings, tyres and trailer brakes

The last concrete at a South Coast boat ramp is a forensic site. One trailer comes off the water, the hubs still hissing, and the owner winds the jockey down and goes for a pie. Another owner pulls the dust caps, sees milky grease, and cancels the drive home. The second owner is the one whose bearings last. The first owner is why parts houses stock complete hub assemblies on Saturday morning.

Wheel bearings, tyres and trailer brakes are taught as three jobs. On the road they are one rotating assembly. They share heat, they share water, and they fail in the same week when a hub is neglected. This is Australian workshop practice for light trailers — not a workshop manual, and not a substitute for the torque figures that came with the axle.

The hub is a water and heat problem

A taper-roller trailer hub is a simple machine. Two bearings, a spacer or a shoulder, grease, a washer, a nut, a pin or a lock, a cap. It fails when the grease is gone, watered, overheated or the nut was last set by optimism.

Play and rumble are the two honest symptoms. Jack the wheel. In-and-out play at the rim is adjustment or wear. A gritty rumble as it spins is a race. A hub that is too hot to hold after 20 kilometres, when its pair is warm, is a dragged brake or a bearing on the way out. Stop.

Water gets in from the back of the hub as often as from a missing cap. Boat ramps, flooded crossings and a hub run under a high-pressure hose all count. “Bearing buddies” and similar pressure caps can help keep water out if they are maintained at the right pressure. Over-pumped, they shove the inner seal out and make the problem you were avoiding. If you fit them, treat them as a service item, not as a charm.

Grease has to match the work. A plant trailer that runs hot down the Toowoomba range wants a high-temperature wheel-bearing grease. A boat trailer that is immersed wants a water-resistant or marine-duty grease the hub maker accepts. Chassis grease from a farm drum is not a substitute. Do not mix a calcium marine grease over a lithium fill and hope. Clean, pack, and assemble to the nut’s specified feel — typically snug, then back to the first pin hole, not “as tight as a wheel nut”.

If you are writing a maintenance calendar rather than standing under a hub tonight, put pack intervals into the yearly service schedule. Boat-specific set-up lives in rollers, bunks and ramps.

Tyres carry GTM, not optimism

Trailer tyres fail from load, age, pressure and alignment, in that order.

Load index is read against GTM, divided across the tyres that actually sit on the road. A tandem with one soft tyre is a three-tyre trailer until the remaining three confess. The plate on the drawbar should state tyre size and pressure. If it does not, you are already in plate literacy trouble.

Age matters in this climate. A trailer that sits in a Dubbo yard for eleven months still cooks its tyres in the sun. Read the week-and-year stamp. Replace on age if the rubber has gone dull and cracked, even if the tread looks honest. Sidewall cracks on the inner face are the ones people miss.

Pressure is a cold, laden number. Too soft and the tyre builds heat until the belt lets go at 100 km/h. Too hard and you lose the contact patch on corrugations, then you blame the shock absorbers the trailer never had. Recheck after the first inland afternoon; pressure rises with heat, and a “high” reading on a hot tyre can still have started low.

Wear patterns are a message from the axle. Inner-edge wear is a shifted leaf, a bent spindle, a tandem not sharing, or a brake that drags and cooks one shoulder. Cupping is play in a bearing or a bush. A tyre that eats itself on one side of a close-coupled tandem is often an equaliser or a U-bolt, not a “bad batch”.

Carry a spare that matches. A temporary space-saver from a car is not a trailer spare. Torque wheel nuts in a star pattern after the first 50 kilometres of a trip, and again after corrugations. The yearly schedule treats that as a reflex, not as a tip.

Brakes: the third heat source in the same drum

Most Australian light trailers still use electric drums. The magnet wipes a face; the shoes open; heat stays in the drum. That is fine on a dry highway if the controller is set so the trailer helps the vehicle. It is unkind after a beach launch, because the drum is a bowl of grit, salt and the last of the grease that walked out of a warm hub.

Override hydraulic systems put the master cylinder in the coupling. They need a slider that moves, a damper that still damps, and shoes or pads that are adjusted. They do not need a cabin controller, which is why they are popular — and why they are neglected. A seized slider is both a brake failure and a coupling failure.

Discs, electric-hydraulic or power-hydraulic, throw water off better and then grow a rust glaze if the trailer sits. A first application after winter can feel like there are no brakes until the glaze clears. Do that in the yard.

Air and full hydraulic power belong on heavier plant. Their service is a different culture: gladhands, tanks, valves. If your custom trailer has grown into that world, you have also grown out of a casual backyard adjustment. See the legal bands in when your trailer needs brakes.

Adjustment is not optional. A drum that only works after the third stab of the pedal will let the trailer steer the vehicle — the start of the story in weight-distribution and sway. Electric magnets wear. Linings glaze. One tight wheel will cook a bearing. When you pull a hub to pack it, look at the brake that lives around it. That is the point of treating them as one assembly.

Breakaway batteries go flat on trailers that sit. Test the pin. A dead breakaway on a trailer over 2,000 kg GTM is not a paperwork issue. It is the emergency system.

Salt, corrugations and long heat

Three Australian conditions do most of the damage.

Salt. Wash with fresh water the same day, including the back of the hub and the inside of the drum if you can get to it without destroying a seal. Then decide whether the launch was deep enough to demand a pack. Coastal parking without launching still salts the lamps and the springs; that is a rust job as well as a bearing job.

Corrugations. They undo wheel nuts, U-bolts and plug earths, and they hammer races that already had play. Re-torque after a dirt stage. Listen. A new hum that changes with speed is rarely “just the road”.

Long heat. Inland bitumen at 40 °C plus a loaded GTM is how under-pressured tyres and dragging shoes become a fire lane. Rest on long climbs. Put a hand near the hubs at the top of the range. If one is savage, stop.

Workshop manners that keep all three alive

• Do not spin a hub on a grinder to “clean it up” and then reuse a damaged race.
• Do not hit a dust cap with a hammer in a way that showers the bearings in filings.
• Do not reuse a crushed seal because the new one is in town on Monday.
• Do not paint a drum or a disc.
• Do not mix wheel nuts across imperial and metric studs on a used tandem.
• Do not set electric gain so high that the trailer parks the vehicle, or so low that the drums never work and the vehicle does all the heat.

If you are specifying a new trailer, buy an axle with a serviceable hub, a known seal, and brakes that match the GTM band. Ask the builder how the drums drain, how you will reach the adjusters, and whether the spare is a real wheel. Those questions belong in questions for trailer manufacturers.

This is practice, not a repair manual and not legal advice. Use the component maker’s figures. If the brake system is a plated ADR 38 item, have it serviced by someone who will stand behind the adjustment.

When the rotating assembly is honest, the rest of the trailer’s longevity is rust, fasteners and washing. Continue with preventing rust on Australian trailers and keep the maintenance hub for the calendar view.