How do I stop my motorhome from swaying?

In this short guide, we will answer the following question: How do I stop my motorhome from swaying? We will explain why motorhome swaying happens and how to prevent and fix it. 

How do I stop my motorhome from swaying?

To stop your motorhome from swaying you’ll have to use anti-sway bars and shock absorbers. The transfer of load between wheels on the same axle can affect the balance of the vehicle. This is why you need anti-sway bars, but how does it work?!

We’ll do our best to explain how an anti-sway system for a motorhome works in just a few points:

  • For a motorhome to take a corner, a lateral force is required to act on the front and rear axles. Normally, this force is identical on both axles, they both rotate at the same rate, and the motorhome adopts a ‘neutral’ attitude when tackling the curve.
  • The suspension of the motorhome is designed so that the maximum lateral force that the front axle can withstand is less than that that the rear axle can withstand. The result is the so-called understeer: as the front axle cannot use as much force as the rear axle to turn… the motorhomes begin to sway. 
  • The active stabilizers allow the transfer of load from the outer wheel –which has greater adhesion– to the inner one –which has less -, thus reducing the maximum transverse force that the axle can withstand. On the front end, that increases understeer; on the end, it reduces it.

Note: If the motorhome does not drive straight and sways sideways even after installing an anti-sway system, have the brakes checked by a professional as soon as possible. 

Why is a motorhome swaying?

The first reason why a motorhome is swaying is that the chassis, cabin and powertrain are supported by suspensions. By being able to be compressed, the suspensions allow the set of all the above, called ´the suspended mass´, to tilt sideways – also up and down, the so-called pitch, but this time we are going to focus only on the swaying

When swaying, the suspended mass tilts about an imaginary longitudinal axis that passes through two points: the front and rear roll centres. The position of these points is determined by the geometry of the suspension. 

In the case of a vehicle with rigid axles, the centre of the roll is always in the centre of the axle. On motorhomes with more elaborate suspensions, the roll centre shifts a bit during roll but is still roughly between the wheels.

Most of the motorhome’s weight – and therefore also its centre of gravity – is located above both roll centres. So every time the motorhome tackles a curve, a force appears that forces the entire body to tilt along its roll axis.

 If the centre of gravity of the suspended mass of a motorhome were at the same height as the roll axis, the motorhome would turn flat. And if it were below, the vehicle would tilt ‘backwards’ in curves … much like someone swinging in a hammock. 

In other words, the rocking motion of the body is a consequence of the lateral acceleration it experiences … and this, in turn, depends on the speed at which the curve is taken and its radius.

Why is swaying a bad thing for a motorhome?

A motorhome swaying on the road is an undesirable movement because it causes several negative effects that we are going to analyze. The first and most obvious of all is that it increases the risk of tipping, especially in larger motorhomes, where there is a greater distance between the centre of gravity and its roll axis.

The second is that the movement that the virtual roll axis experiences as roll increases reduces the stability of the vehicle and makes its behaviour less predictable for the driver. In addition, excessive roll affects passenger comfort and driver confidence.

The third is that roll affects the camber angle of the wheels – the angle that the vertical plane of symmetry of the tire forms with the vertical, at the point of contact with the asphalt.  By reducing this angle – even going as far as negative – you reduce the tire surface in contact with the road and, with it, the available grip.

The most common way to alleviate motorhome swaying is by using anti-sway bars. An anti-sway bar is a U-shaped steel tube that interconnects the wheels of an axle.

The stabilizer bar compensates for sway because as the suspension on one side compresses, it forces the suspension on the opposite side to compress as well. In fact, an infinitely rigid stabilizer would cancel out the swaying entirely. The anty-swaying bar is technically said to ‘increase the roll stiffness of the axle’.

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However, the stabilizer bar is not a ‘perfect solution. A too rigid stabilizer subjects the occupants to constant lateral accelerations that can quickly cause dizziness. 

In addition, the presence of the stabilizer means that any bump approached only with the wheels on one side has an effect on the body similar to that of a non-existent lateral acceleration. This fact, called road copying, prevents the suspension from doing its job well, which is to minimize the vertical movements of the motorhome.

One way to resolve this apparent contradiction is to actively control motorhome swaying using a mechanism that allows the suspension roll stiffness to be adjusted in real-time.

How to handle swaying motorhomes in high winds?

If your problem is that the motorhome is swaying in high winds, you must learn how to secure your RV so that you are completely safe on the road.  In this case, it’s not about anti-sway bars or a brake problem, it’s more about learning how to manage your motorhome when the weather is not that friendly. 

There are several ways to secure your RV in high winds. Just follow these tips:

  • Close the roof hatch, windows and zippers – In the event of strong gusts of wind, avoid damage by closing the roof hatches and the windows of the RV. With moderate wind, you can still leave it ajar. With a tent/awning, it is important to close the zippers properly so that the wind cannot hit from below.
  • Store your stuff – The wind can sometimes cause things to disappear on the campsite. Store your light belongings, such as linen, bath towels, inflatable mattresses and inflatable swimming pools in the tent or caravan. 
  • Determine the direction of the wind – Knowing where the wind is blowing will help you prevent your reactions in time. To orient yourself, it is imperative to refer to the signs on the side of the road. 
  • Check the tires – To compensate for the lack of traction, it is essential that your tires are in perfect condition, both wear and pressure. This is especially important if windy and stormy episodes are common in your area. If you need to change them, you can buy tires online without having to go to the garage.
  • Know your vehicle well – The vehicles most sensitive to side wind gusts are those with a higher body and larger side area. RVs are more difficult to control due to their size and higher centre of gravity. If this is your case, it is important to be extra vigilant.
  • Keep your hands on the wheel – In windy conditions, never take your hands off the wheel. You can’t trust that feeling of control of the vehicle that you can have. 

Make sure you read our article on how to secure an RV in high winds for more useful tips. 

The bottom line

A swaying motorhome can be a real danger on the road, both for you and for other drivers. If you notice that your motorhome is swaying it is best to ask for guidance from an authorised mechanic to seek the issue and fix it as quickly as possible.

If you have any questions, comments or suggestions on stopping a motorhome from swaying, please let us know!

FAQ on How do I stop my motorhome from swaying?

Do airbags help with sway?

Airbags do not help with sway. What you have to look out for is if you have anti-sway bars installed or whether you have loaded your trailer correctly. An overloaded weight can cause the vehicle to sway. 

What do sway bars do on a motorhome?

An anti-sway bar is a U-shaped steel tube that interconnects the wheels of an axle. The stabilizer bar compensates for sway because as the suspension on one side compresses, it forces the suspension on the opposite side to compress as well.

How to drive with a motorhome?

To drive with a motorhome, you have to know the following tips:

  1. Know its dimensions. It is as basic as it is fundamental.
  2. Spread the load evenly. 
  3. Avoid overtaking.
  4. Drive at a steady speed. 
  5. If there is a strong wind, slow down. 
  6. Use the side mirrors. 
  7. Do not leave loose items inside.

References

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