It is not unusual for caravan owners to increase the load in their rigs over the years with new appliances and whiz-bang new parts.

A strange, occasional noise was a tyre hitting the top of the wheel arch when a pothole jumped up and smacked it.

Solution to the tyre hit mudguard problem is removing the axle from on top of the springs to under the springs.

Works a treat, problem solved or did I open up a can of worms.

Legal or not Legal?


Raising the height could affect your annexe height. You may have noticed your annexe height getting smaller over the years.


Insurance cover and manufacturers quickly void the warranty if you have changed the manufacturer’s specifications.

Couplemate as a manufacturer would consider warranty immediately voided in cases where a product is changed.

The warranty can be held intact if the change is approved in writing. Ask your manufacturer if he can approve the change via a  simple email.


Caravan manufacturers install your axle on top of the springs for safety reasons. U-bolt clamps installed correctly and re-tightening after the settling period should last forever.

When u-bolts are manufactured incorrectly, u-bolt breakage can make everything go horribly wrong; u-bolts may suffer from hydrogen embrittlement. (Google: Hydrogen Embrittlement) It occurs when steel is bent and not de-stressed.

Axles installed on top of the spring are fixed within the boundaries of the springs, should u-bolts break.

Axles that are under-slung will detach from the caravan upon u-bolt breakage with disastrous consequences.

Under-slung has been a hot topic for decades, but now you have industry opinion.

There are other alternatives should you want to change your caravan height.


Check your spring height. Ring your manufacturer and ask him about your spring camber height.

If you draw a line across the top of you spring eyelets and drop a perpendicular from the centre, this measurement is your camber.

Camber can be as much as 120mm. If your springs are flat, then your answer may lie in spring replacement because you have little or zero camber.

Longer shackle plates

Another myth is longer shackle plates will lift your caravan height.

No, that does not work either. Your hangers are welded into position according to you spring length, rocker centres, and shackle length. Change any one one of these, and you change your spring dynamics and performance.

Is there a Safety Standard for U-bolts in Australia? No, there is NO Safety Standard for U-bolts. However, Couplemate decided to make a testing standard due to stress fractures caused by hydrogen embrittlement.

How does Couplemate test u-bolts and how strong are they?

We test our 5/8″ heavy-duty u-bolts to breaking capacity of 23t. The machine used has a capacity of 200t.

In the image below we tested 2 x 5/8″ -bolts coupled to a 10mm Fish-plate and tightened the bolts with nylocks.

We rated our 5/8″ u bolts kits to a working capacity of 2.25t.

After galvanising, U-bolts are batch tested after they have been de-stressed in an oven.

Finally, purchase a pair of small safety chains, if you do decide to under-sling your axle. Weld the chain between axle and chassis, in the centre of the spring.

More tips and tricks can be found on our help page

Axle under Springs to raise Caravan Height