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Trailer Brake Drum, Hub & Backplate Assembly Guide UK Safety

Correct trailer brake drum hub assembly is essential for safe towing, even braking and long component life. Poor maintenance can lead to seized brakes, overheating hubs and bearing failure — all of which can quickly turn into roadside breakdowns or dangerous situations.


This guide walks through inspection, strip-down, servicing and reassembly of trailer brake drums, hubs and backplates, with specific advice for UK trailers using either taper roller bearings or modern unitised hub bearings.


⚠️ Important Safety Note Before You Start

If your trailer coupling uses an over-centre handbrake, it is ESSENTIAL that:

  • The handbrake lever is securely tied down

  • Locking pins or stop pegs are fitted exactly as specified by the manufacturer

This must be done before dismantling any braking components. Failure to do so can cause sudden release of stored energy and serious injury.



Identify Your Trailer Hub Type First

Before stripping anything down, confirm which hub design your trailer uses:


Taper Roller Bearing Hubs (Older Design)

  • Adjustable bearings

  • Periodic cleaning and re-greasing required

  • Castellated nut and split pin


Unitised / Sealed Bearing Hubs (Modern Design)

  • Sealed for life

  • Non-adjustable

  • Single-use flange nut

  • High torque settings required

The service procedure differs significantly depending on the hub type.


Trailer Brake Drum & Hub Inspection Procedure


1. Jack Up and Secure the Trailer

  • Jack the trailer and support it on axle stands

  • Grasp the wheel at the top and bottom and rock it

  • Any lateral movement indicates bearing wear or incorrect adjustment


2. Remove the Wheels

  • Remove all road wheels to expose the brake drum and hub assembly


3. Check Brake Linings

  • Inspect brake linings through backplate inspection holes if fitted

  • If linings are visible and in good condition, full strip-down may not be required

  • If inspection is not possible, continue and remove the brake drum


4. Remove Grease or Dust Cap

  • Exposes either:

    • Castellated nut (taper roller bearings)

    • Flange nut (unitised bearing hubs)


5. Remove Drum and Bearings

Taper roller bearing hubs

  • Remove split pin

  • Undo castellated nut

  • Remove thrust washer if fitted

  • Withdraw drum complete with bearings


Unitised bearing hubs

  • Undo the single-use flange nut (often extremely tight)

  • Remove the drum and bearing unit as one assembly

Tip: Back off brake adjustment if the drum does not slide off easily.

Bearing and Hub Checks


Taper Roller Bearings

  • Remove front and rear bearings (rear may remain on stub axle)

  • Clean using degreaser or paraffin

  • Inspect rollers for flat spots or damage

  • Check inner oil seal and replace if damaged


Bearing Cones

  • Clean and inspect inner and outer cones

  • Replace if worn

  • Follow hub manufacturer installation instructions carefully


Unitised Hub Bearings

  • No servicing possible

  • If faulty, the entire unit must be replaced

  • Some replacements require specialist pressing equipment


Brake Drum & Backplate Assembly Checks


Brake Drum

  • Inspect inner braking surface

  • Check for:

    • Rust build-up

    • Excessive scoring

    • Cracks or distortion


Brake Backplate

  • Clean thoroughly with brake cleaner

  • Remove all brake dust and debris


Brake Springs

  • Inspect for corrosion or breakage

  • Replace if weakened or damaged

  • Note original component positions before removal


Shoe Carrier and Expander

  • Ensure components slide freely

  • Clean and apply a small amount of specialist brake grease (e.g. Copperslip)

  • Do not allow grease to contact brake linings


Brake Linings

  • Minimum lining thickness: 1.5mm

  • Check for uneven wear or contamination

  • Replace if necessary and refit exactly as removed


Bowden Cables

  • Check for smooth operation

  • Inspect for kinks, fraying or seized inner cables

  • Replace damaged cables in pairs


Most modern Bowden cables are self-lubricating. If grease nipples are fitted, apply grease sparingly to avoid lining contamination.

After fitting new cables, apply the handbrake firmly at least 10 times to remove initial stretch.



Re-Greasing and Reassembly


Bearings

  • Re-grease taper roller bearings using:

    • High melting point grease

    • Water-repellent grease for boat trailers


Refit Drum – Taper Roller Bearings

  • Refit drum and bearings

  • Install thrust washer

  • Tighten castellated nut until slack is removed

  • Do not overtighten

  • Back off to nearest split-pin slot

  • Ensure hub spins freely

  • Fit a new split pin

  • Lightly grease and refit dust cap


Refit Drum – Unitised Bearings

  • Lightly oil stub axle threads

  • Refit drum and bearing unit

  • Fit a new flange nut

  • Tighten using a torque wrench to manufacturer specification:

  • AL-KO – 290 Nm (214 lb-ft)

  • Ifor Williams – 350 Nm (260 lb-ft)

  • Avonride – 280 Nm (200 lb-ft)

High-capacity torque wrenches are required due to the very high torque values. Correct tightening automatically sets bearing preload.


Final Assembly Checks

  • Repeat the procedure on all hubs

  • Refit wheels and lightly tighten wheel nuts

  • Lower trailer to ground

  • Torque wheel nuts using the correct tightening sequence


Final Advice

Regular trailer brake drum hub assembly inspections reduce the risk of seized brakes, uneven braking and bearing failure. Always refer to brake and hub manufacturer maintenance instructions and service trailers on time intervals — not just mileage.

Proper maintenance keeps your trailer legal, safe and ready for the road.

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