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Stretching U-Bolts cause Caravanning Problems

by | Jun 28, 2019 | Trailer & Caravan Safety | 0 comments

Stretched U-bolts are easily fixed. However, unforeseen issues can have disastrous consequences when towing a trailer or van if left untouched.

The humble U-bolt clamps the spring to the axle on trailers and caravans. This bond between the spring and the steel beam prevents catastrophic events at high speed. Therefore, it is of utmost importance to inspect this connection during servicing.

For example, the image below looks like there is something wrong. If you cannot pick the problem, keep reading for more information.

Do you think the service mechanic noticed the nail in the centre tyre?

Basic Observations

The example image pictures an axle with the following specifications:

What is wrong?

The following issues can be identified here:

  1. Leaf separation between leaves 2 and 3 can indicate stretching U-bolts.
  2. The space between the axle pad and the axle confirms stretching U-bolts.

Service Tip

Did you notice the spanner on the ground and not a rattle gun?

Experienced caravan and camper trailer service mechanics do not use rattle guns on U-bolts. Although a powerful battery rattle gun is available, in this instance, a spanner is the most useful piece of equipment.

Rattle guns create heat, which can cause the nylon ring inside the nylock nut to burn and become ineffective. Additionally, the power of the rattle gun can cause the nylon ring to pop out of the nut.


If you notice your trailer or caravan has stretched U-bolts, you can implement the following simple solutions:

  • Replace the nylock nuts
  • Retighten the u-bolts in a diagonal rotation until the fishplate starts to bend.

Following these steps, each service will resolve caravanning problems with U-bolts. If you are unsure about checking the U-bolts, call your service technician to book a service before your next trip. It may just save your life.

Finally, did you notice the spring wrap from the main image below? It has opened a little. The spring warping causes this during reversing.

Tight U-bolts are critical in preventing spring warp and will prevent these spring wraps from opening.

In conclusion, always mention U-bolt tightening checks to your service mechanic during your caravan services, and you will not experience these critical caravanning problems.

You can read another helpful article about the causes of significant highway accidents here or learn more about broken springs, couplings and jack-knife trailers.

broken spring

Stretching U-Bolts Cause Caravanning Problems

© Steve Wotherspoon 28th June 2019


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