Video – Why Do Some Trailers Tow Stable?

The way a trailer tows makes a big difference in the ownership experience.  So, Why do some trailers tow stable, while others do not?  Even a small trailer that does misbehaves by swaying is rather intimidating on the highway, and a lot of work to tow.  Bigger trailers that waggle are downright dangerous.  (Of course, that does depend on the severity of the waggling.)  Many people call this “Trailer Sway”, or “Fishtailing”.

On a recent trip, I caught one such small trailer waggling away behind the tow vehicle rolling down the highway.  My wife was a great sport and took this video for you.  It’s a little shaky, but, with the help of YouTube stabilization, not too bad.

Learning From Another Example

Look at the trailer and how it tracks behind the tow vehicle.  For the most part it follows well, but when there is an small interruption — like going around this curve, or a bump, a minor steering correction by the driver, etc., the trailer fishtails just a little.

This vehicle caught my attention when the driver changed lanes and the trailer did a pronounced waggle.  Fortunately for them (unfortunately for the video), the driver did not do that again while we watched.  Nevertheless, you can still see some tail wagging in the video as they round this bend.

For reference, this waggling from side to side is called Yaw — one of the important vehicle attitudes.  Important, but not desirable (except in a purposeful full drift!)

This waggle is actually not that bad.  However, I’ll bet the driver feels some weird steering inputs and probably has to fight it just a little from time to time as they drive.  That said, a little can be a lot if it makes the driving more stressful.

Making Trailers Tow Stable

What makes some trailers tow stable, while others waggle down the road?  We wrote a full article about Trailer Stability, (with related trailer design articles) still posted on our parent site Synthx.com.  It’s a good place to start reading.

For the one in the video, it’s hard to say exactly the cause of the semi-stable behavior just by looking.  However, I will guess it is poor loading.  Probably the center of mass is too far back leaving insufficient tongue weight.  Also, (not in the video) the trailer tongue is pretty short, which can amplify loading (and stability) issues.  See the post on setting the right axle position with discussion on loading for more on making trailers tow stable.

Of course, there are likely some other contributing factors.  Look at the weight distribution side to side.  Again, this is not a big deal by itself, but the right side motorcycle is bigger, and probably heavier than the left.  (Note the motorcycle rear tire size.  Typically a bigger tire means more HP, and therefore likely more weight, though these are guesses.)  With all that, I’ll bet if they stop and redistribute the trailer contents for a more centered (side to side) and slightly forward center of mass, then this trailer will be much more stable and enjoyable to tow.  While it would be fun to show them on the spot, I’m sure the intrusion would not be welcome.  Oh well.

I will give them props for securing the load well.  As another driver on the road, I really appreciate it when folks take the time to strap down and secure their loads.  Stuff flying from trailers (or vehicles for that matter) is no fun.  Thank You.

Other Contributors In Making Trailers Tow Stable

Other typical contributors (not shown in the video) include wheels, tires, axles, and alignment.  Those are in a section by themselves below.

Aerodynamics can also play a role especially in highway cross winds.  Large profile trailers can get a push by a wind gust, or even by air flow around a larger vehicle on the highway.  Wheelbase also plays a part.  Longer is usually better — if you get the other contributors right.

Finally, the tow vehicle is important — especially when the trailer size exceeds the tow vehicle size.  The bigger the waggle, the more it takes to control it, so make sure your vehicle is good for it.  Too often, the little waggle will  flip the whole system — that’s now where we want to be.  The closer the rear wheels are to the hitch point, the better also.

The key in all of this — It’s never just one thing.  It involves the whole system of car and trailer.  And the smartest way around it is to stack the deck in your favor for stability on the road.

There is so much more information on this topic of trailer sway and stability.  For starters, I highly recommend the article Trailer Sway – Video Review and Discussion.

When It All Goes Wrong

Stability is more than just a buzz word.  As mentioned above, minor instabilities are mostly just an annoyance that make towing less pleasant.  On the other hand, when we think of it as teetering the balance toward disaster, it has a different light.

The example in this article about safety chains is a stark reminder that all the details matter.  It’s never just one thing, it’s the whole of circumstances and situation.  That’s highlighted even more in this article from several news stories about dangling from a bridge by just one trailer chain.  Though I don’t have proof, I suspect weight stability is one of many contributors in both these accidents.  It’s really no joke.  Perhaps both could have been avoided a with setup so the trailers tow stable.

Don’t Forget Wheels And Tires

While it does not appear to be an issue with this trailer, one other factor to help trailers tow stable is the wheels and tires.  Without going into much detail, here are a couple thoughts.

First, tire pressure makes a difference.  One side low and one side high will make the trailer do weird things when you hit a bump or swerve.  So, make sure the tire pressure is right, and the same on both sides of the trailer.  Tire pressure is also very involved in trailers that bounce.  That’s a different kind of stability.

Second, if a trailer wheel is not balanced, or if one gets damaged, like bent, the trailer will wander — especially at speed.  Have the wheels balanced and inspected once in a while.

Finally, for multi-axle trailers — tandem and triple — make sure the axles are parallel with each other, and perpendicular to the direction of travel.  Straight and square as they like to say.  Misaligned axles will not only cause weird dynamics and the trailers may not tow very stable.  They will also wear out tires fast.

For more about tires, read this about choosing trailer tires, and this about spares.  Enjoy.

Comments

1 Comment
Inline Feedbacks
View All Comments

We Found These For You . . .

Article
Review of the Folding Trailer Tongue
On a recent trailer, I experimented with a new folding tongue design.  Now it’s time to review — What do I like?  What would I do different if building another?

Read The Article

Article
All The Steel Cut And Ready For The Trailer Build
Update on building a new design specialty utility trailer.  The trailer build is going well, and we thought you might have interest in following the progress.  Especially for some of the experimental new concept features.

Read The Article

Article
There's More To Just Mounting Trailer Axle Springs
As with many things, there’s a lot more to mounting trailer axle springs than first meets the eye.  Here are 2 tips to make your trailer frame stronger.

Read The Article

Article
Trailer Wiring For Breakaway Kit
What in the world is a Trailer Breakaway Kit?  If you pull a “larger-ish” trailer, you should definitely know, because it’s a legal requirement in many jurisdictions.

Read The Article

Article
Ways to Make a Trailer Wider
So, I have this trailer, but it needs it to be bigger.  Is it possible to make a trailer wider?  Can I make it wider to carry more?  And, what are the limits or problems with making it wider?

Read The Article

Article
How To Stop Utility Trailer Bounce
If you pull an empty (or nearly empty) utility trailer, you probably know the feeling of utility trailer bounce.  It’s that bumpy jolting extra bouncing you feel in the tow vehicle as you drive.  Sometimes it feels like the trailer…

Read The Article

Article
What Do You Want for 2020
A new day, A new Year, and a new Decade!  We don’t get to say that very often, so it’s kind of cool.  Anyway, as we look to the near future for Mechanical Elements, we want to know what you…

Read The Article

Article
Engineered Trailer Plans Are Not Free Plans
It’s a big dilemma.  Why buy trailer plans (or crane plans or whatever) when you can get free plans?  Some websites have free plans, other places charge.  So what’s the big deal? 

Read The Article

Article
As a simplistic introduction to beam loading, this article discusses the complications in calculating stresses and deflection.  While it’s pretty easy to calculate beam loading for simple theoretical cases, very few beams

Read The Article

Product
Tilt Top Trailer Conversion

Build a Tilt Trailer by 'Converting' our standard, single axle Utility Trailer Plans.  Works with our 6' and 6'10" width, 3500# Trailer Plans, and is compatible with both leaf springs and torsion axles.

Article
Do I Need A Trailer Spare Tire?
What about that trailer spare tire?  No, I don’t mean the one around my middle . . . for your trailer.  Do you really need one?  Some say yes, and we see them on many trailers, but they are rarely…

Read The Article

Article
Build it with Torsion Axle Trailer Plans
New Product Announcement:  The Mechanical Elements line of DIY Trailer Blueprints has just expanded with some new sizes for Torsion Axle Trailer Plans.  You ask, then we work to deliver.

Read The Article

Article
May Is Build Month - DIY Plans Sale
May, the time of new flowers after April showers, is also the time for building that project you’ve been stewing on over the winter.  Spring has sprung, so it’s time to make it happen.

Read The Article

Product
32' Tiny House Trailer Plans For DIY

With options for length, these blueprints address the unique needs of a Tiny House Trailer.  Low 8.5’ x 30’ or 32’ top deck height.  Up to 18,000 lbs total capacity.  Fully Engineered.

Article
Folding Trailer Tongue Finished
Intrigued by the cool potential of saving storage space, increased security, and removal of a shin knocker to step over, this new folding trailer tongue adds greater utility to a trailer.

Read The Article

Article
DIY Steel Cutting Options
So, you need to cut steel for a DIY project (like a crane or trailer).  Easy, Right?  What’s the best, easiest, cheapest, fastest way of cutting steel?  There must be dozens of ways, so, the better question might be

Read The Article

Product
Torsion Axle Conversion

Convert our 6' 10" Width, 3500#, Single Axle trailers to use a Torsion Axle instead if leaf springs with these Conversion Plans.  Build with confidence using engineered plans.

Article
Using A Workshop Hydraulic Press
A shop press is a fantastic tool, and when you need it, there’s not much that can really substitute.  On the other hand, we need to keep things in order because when things go bad, they can easily go really…

Read The Article

Article
Twisting Trailer Safety Chains
Should you twist trailer safety chains to make them shorter?  Certainly twisting them reduces the length so they don’t drag the ground.  That part is good.  However, there are big issues with twisting safety chains?

Read The Article

Article
How We Make The Plans
What goes into the engineering of Do It Yourself Plans?  How do we make them?  When you purchase and download project plans from Mechanical Elements, you get a TON of work and information, much more than first meets the eye.

Read The Article