50mm Square Galvanised U-Bolts

SKU: N/A Category: U-Bolts and Kits Tag: U-bolts Brand: BoltBiz

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Caravan U-Bolt: 50mm Square – With Gal Nylocks and Gal Washers

The 50mm square U-bolt is a sturdy and reliable option for securing jockey wheels to caravans and boat trailers.

Made from galvanised steel, it resists rust and corrosion.

The caravan U-bolt: 50mm square, 75mm long, features galvanised nylocks and washers, ensuring a secure, tight fit. Its square shape provides added stability and strength, making it a popular choice for heavy-duty applications.

We carry a good stock of Premium 50mm Square U-Bolts for immediate Express Dispatch.

U-bolts, washers, and nylocks are galvanised to resist corrosion and are suitable for marine environments.

Further, the 50mm square galvanised Australian U-bolt has rolled threads instead of cut threads. Additionally,

the thread length is 60mm.
The thread size is 1/2 inch BSW.

Purchase U-Bolt kits with clamps here.

50mm Square U-Bolt Lengths

75mm x 50mm
100mm x 50mm
115mm x 50mm
125mm x 50mm
137mm x 50mm
150mm x 50mm
165mm x 50mm
175mm x 50mm
200mm x 50mm
250mm x 50mm

Four elements uniquely define any U-Bolt:

Material type (for example, bright zinc-plated mild steel or galvanised)
Thread dimensions (for standard 1/2 inch )
Inside diameter (for example, 50 mm – the distance between the legs)
Inside height (for example, 125 mm)

Mild steel stretches under load. You must re-tighten the U-bolts about 200 km after installation.

Loose U-bolts cause accidents

Vibration fatigue can loosen U-bolts if not re-tightened after 300 km.

Excellent article on vibration fatigue here.

How U-Bolt Sizes Are Measured

Measure from the inside of the U-bolt or the width of the tube.

For example, the 250mm U-Bolt Kit is 250mm when measured from the thread’s tip to the top’s underside.

The U-Bolt kit comprises

1 x galvanised U-Bolt
2 x galvanised Washers
2 x galvanised Nylocks

Mild steel stretches under load. You must re-tighten the U-bolts about 200 km after installation.

Specifications: Caravan U-Bolt: 50mm square

The thread length is 50mm.
The thread size is 1/2 inch BSW.

Also, review U-Bolt kits with clamps in our trailer parts shop

Galvanised U-Bolt Square Clamp Kits are listed below

Boat Trailer 50mm U-Bolts FAQ

Q: How do I correctly measure a 50mm U-bolt to ensure a proper fit?

To confirm you are buying the correct size, take your measurements from the inside of the hardware:

Internal Width: Measure the inside distance between the two legs; a 50mm U-bolt measures exactly 50mm inside to fit cleanly over a 50mm axle or chassis rail.
Internal Length: Measure from the inside top curve down to the tip of the threaded legs.
Thread Clearance: Ensure the length leaves roughly 10mm to 15mm of visible thread past the nut once fully torqued.

Q: Why is a galvanised or Dacromet finish necessary for boat trailers?

Marine environments subject your trailer to harsh saltwater conditions, requiring specialised protection:

Corrosion Resistance: Hot-dip galvanised and Dacromet coatings provide a thick barrier that actively resists rust.
Structural Longevity: Prevents premature weakening of the metal caused by oxidation.
Safety: Eliminates hidden rust failure points, securing your heavy watercraft during highway transit.

Q: What is the load rating for standard 50mm boat trailer U-bolts?

Load ratings can vary by manufacturer, but heavy-duty 1/2-inch rod variations typically follow these standards:

Individual Capacity: Commonly rated at roughly 375kg per individual U-bolt.
Axle Set Capacity: A complete setup of 4 U-bolts on a single axle distributes a total rating of up to 1500kg.
Tensile Steel Strength: High-quality kits use 1045-grade tensile steel that can handle high structural stress.

Q: Should I use Nyloc nuts or standard nuts with spring washers?

Both methods are widely used on Australian trailers to combat road vibration, offering unique advantages:

Nyloc Nuts: Feature an integrated nylon collar that locks the thread tightly without needing extra washers.
Spring Washers: Combine flat washers with a split spring washer to maintain tension against a standard nut.
Best Practice: Always hand-tighten your nuts evenly across the plates; avoid using air impact wrenches (rattle guns), which can strip or warp the hardware.

Additional information

Weight	0.4 kg
Dimensions	10 × 10 × 2 cm
U-Bolt Length	75mm, 100mm, 115mm, 125mm, 140mm, 150mm, 165mm, 175mm, 200mm, 250mm
U-Bolt Width	50mm
Torque	1/2-inch – 60Nm
U-Bolt Application	Spring U-Bolts
Thread Length	45mm
Nut Type	Nylock
Coating	Galvanised

Our Service Lifetime Warranty

Our goods come with guarantees that cannot be excluded under the Australian Consumer Law. You are entitled to a replacement or refund for a major failure and compensation for any other reasonably foreseeable loss or damage. You are also entitled to have the goods repaired or replaced if the goods fail to be of acceptable quality and the failure does not amount to a major failure.

Couplemate™ is a manufacturer and vendor of high-quality towing, trailer, and caravan components. Couplemate™ Core Goods and Custom Work are guaranteed to be free of defects for the service lifetime of the product when used as intended.

Warranties are non-transferrable and Couplemate™ requires satisfactory proof of purchase prior to issuing a remedy. The full Couplemate™ Warranty Policy can be found in the Terms & Conditions: Section 8 – Consumer Guarantees & Warranty.

Warranties are in addition to your rights under the Australian Consumer Law. If something is wrong with your order, please contact our team.

60-Day Returns

After 60 years of experience, we know that life has its unpredictable moments.

All Couplemate™ orders (online, over the phone, or in-store) have a 60 day period for change-of-mind returns and exchanges. There are some items that can’t be returned and some returns may incur a 15% restocking fee.

You can view our full policy for change-of-mind returns here.