Vibration fatigue in caravans and boat trailers is one of the leading causes of bearing failure, spring failure and failures associated with your running gear.

Have you ever seen an axle wobble in the middle as its owner drives down the highway oblivious to what is occurring under his rig?

This causes axle flex suspension fatigue. Badly manufactured axles are another cause.

The driver probably feels a little vibration or something stranger than the last time he towed but cannot quite put his finger on it?

Have you seen Air Crash investigation and heard them mention vibration fatigue?

Vibration can also occur when axles are too long. Example, 39mm Round Axle @ 2000mm on Max weight of 750kg

The axle beings to vibrate, the vibrations go throughout the trailer and cause numerous problems.

The common problems of vibration fatigue are premature spring ageing, spring collapse, shackle bolt, Bush and spring shackle plate wear, constant bearing failure and bearing collapse and then there are huge problems inside the rig.

vibration fatigue

Now I am only mentioning boat trailers because the addition of rust accelerates vibration fatigue, however, vibration fatigue apples to caravan and camper more so because these Grey Nomads have a lot of equipment inside their camper.

Here are the tell-tale signs of vibration fatigue.

  • 39mm Round or 40mm Square Axle are overweight.
  • Too wide for a 39mm Round Axle would be 1800mm @750kg
  • and 2000mm @ 1,000kg for a 40mm Square.
  • Loose u-bolts are caused by vibration fatigue.

If you have doubts, put a straight edge on your axle beam. If the gap is more than 5mm, you are getting vibration fatigue. The bigger the gap, the bigger the problem.

Get your mate to follow you down the highway and do a small test.

Accelerate to 100 km and have a good look at your axle. Lower the speed and reduce the vibration fatigue.

How do I fix vibration fatigue?

First, you need to identify fatigue as follows:-

  • Bearing Failures and
  • Spring Failures

The following measures can cure fatigue:-

  • Axle upgrade
  • Spring Upgrade
  • Shock Absorbers
  • Top Tip: Let air out of your tyres, say 25 psi on corrugated roads then back to normal pressure on the highway. 

Once your rig is vibration free, then Shock Absorbers are a necessity.

If you have doubts, give us a call, but it is wise to go and get a weight bridge certificate. Manufacturers weights are always under-done.

Add 200kg for fuel and bait and then you are close to your real on-road weight.

If you are thinking about Independent Suspension for your rig, this type of suspension has zero axle flex.

Here is some research data completed some time ago on, 1979 in fact.

Vibration Fatigue in Caravans and Boat Trailers