50mm Square Mechanical Disc Brake


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50mm Square Mechanical Disc Brake Axle

50mm square mechanical disc brake is activated when the tow vehicle engages the override brake.

Disc Options

  • Holden HT
  • Holden HQ
  • Ford
  • 6 Stud Landcruiser Disc Rotor
  • 5 Stud Landcruiser Disc Rotor
  • 6 Stud Parallel Landcruiser
  • 5 Stud Parallel Landcruiser

Bearing Sizes

  • Slimline Bearing Configuration (LM12749/LM68149)
  • Parallel Bearing Configuration (LM68149/LM68149)

Re-check the outer bearing nuts for tightness immediately after the first trip.

Couplemate manufacturers and tests all square mechanical disc brake override axles.

Trailer Parts include

Mechanical Override Disc Brakes are simple brakes to understand and maintain. Ensure brake caliper adjustments are made on the caliper bolt and not the cable adjuster.

Couplemate installs the latest Al-ko calipers on all of our mechanical braking systems.

The force exerted during braking from the tow vehicle engages the override brake, which in turn activates the mechanical calipers causing braking.

Please note: We ask you for your face-to-face measurement of your axle.

The latest news on small axles causing trailer and caravan axle fatigue.

Calculating The Correct Axle Measurements

As a result of viewing the video above, calculate the face-to-face measurement.
  1. Measure the offset wheel. The wheel offset is the distance between the inside of the hub and the outside of the rubber.
  2. Add 50 mm to the offset. Alternatively, choose your own distance between the rubber and the chassis.
  3. Multiply by 2 for both sides. Add your chassis width to the above number.

Metric to Imperial Converter

Convert Imperial (inches) to metric (mm)

  • =

Still unsure of what measurements to take? Check out this handy guide below:

[P] – Check material specifications. What size and profile is the axle (for example, 45mm Square)
[T] – Overall axle length (tip to tip)
[F] – Hub face-to-hub face measurement
[A] – Chassis width
[C] – Tyre clearance
[B] – Back offset
[H] – Tyre to chassis
[G] – Axle pad centres

How To Measure An Axle

Identifying Bearing Combinations

You will also need to identify your bearing combination which can be done by pulling off a hub and bearings and locating the number laser engraved onto the bearing. You will require both the inner and the outer bearing number.

Where to identify bearing number. Look for the laser engraved number on the bearing.



Did you know that the bolts holding in your caliper can unwind on rough, corrugated roads?

Couplemate uses a medium-strength Loctite on all mechanical caliper bolts.

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