How 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?

First, let’s look at two methods for “How” to make it wider, then at the advantages and challenges.

Adding width to a trailer is actually pretty common, especially when converting a trailer originally intended for a different purpose.  A utility trailer to a Tiny House trailer, for instance.  There are two good approaches for widening:

Outriggers (Keeping the Same Track Width)

Starting with a straight bed trailer, weld outriggers to the existing frame.  Usually these go in front of and behind the trailer tires.  While this approach does not change the axle or side to side wheel spacing, it does include a change in wheel wells.  Two important points to get correct:
Using Outriggers to Make a Trailer Wider

  1. Make sure the added width (and expected load) will not twist the main frame rails.  With load on ends, the outriggers will act like a wrench handle trying to twist the main beams.  Placing the outriggers near cross members helps.  Depending on your frame, you may need to add crossmembers to support the main beams near the outriggers.  Or, as shown in image 2, add frame supports.
  2. Think about what the outriggers will support, and what loads they will hold.  If the trailer main beams are torsionally stiff, then just welding outriggers to the side may be sufficient.  (See image 1, and the image at the top of the page.)  If the trailer main beams are less suited, then an additional crossmember or brace under the main beams can help support the outriggers better.  (See image 2.)  The green pieces in image 2 are an example to take the torsional stress off the joint where the crossmember connects to the main beam.

In general, avoid making a trailer wider than the width of the tires.  In other words, don’t make the outriggers or resulting deck go out beyond the tires.  From a stability standpoint, and from a frame stress standpoint, it’s just not the best idea.

Outrigger Variations

Outriggers shown in these images are simple bent metal similar to those you might find under an RV or other box trailer.  They certainly don’t need to have that shape (triangle) or style.  Just straight chunks of tube or channel sticking out will also work great.  See the wood sample below.

These outriggers are shown as simple protrusions sticking out.  The assumption with this construction is that the “box” placed on top will contain some sort of perimeter member.  Outriggers often include a perimeter (outside rail) to support the edge of the deck, or to handle the sides.  Again, see the wood example below.  It shows perimeter members in wood, but those can just as well be aluminum or steel (depending your trailer).

Split Width (Widening the Whole Trailer)

If the entire trailer needs to be wider, simply split the trailer down the middle (front to back).  Cut all the cross members and add middle sections.  Of course, this will also require a new axle because the spring seat distance and track width must get wider.  The important points for this kind of width increase are:

  1. Make sure the cross members are strong enough for the new width.  Longer cross members must be stronger to hold the same load.  Material makes a difference.
  2. If you are simply connecting existing crossmembers, after cutting, the new additional portions must be overlapped for good strong welds.
  3. Create a new “flat” trailer bed.  Be sure, when cross member connections are made, that the new resulting members are straight, square and planer.  Techniques like sistering the cross members are very appropriate here.
  4. Straight Tongue Split Trailer Frame to Add WidthSome additional thought must go into the tongue area.
    • A “V” tongue can also be split then extended to achieve the “V” again, but be careful that the tongue doesn’t get too long.
    • Optionally, the tongue tubes can come off, then reattach (with modifications) after the width change.
    • For a straight tongue, you can cut on either side of the tongue and have two “half” extensions.  Optionally, remove the tongue, widen the trailer, then reset it after.  Strengthen the new tongue mounting after moving the tongue.
  5. Increased width will also have greater need for stiffening the trailer all around.

For this approach, we don’t recommend widening more than a foot or maybe a little more.  It’s presumptuous to think the rest of the trailer is built for a big width increase.  Though it could be.

Other Methods

I’ve seen several combinations of the above put a twist on width increases.  I’ve seen secondary trailer main beams added to the outside of existing main beams, and I’ve seen secondary frames placed over existing frames.  Those are not highlights here because they add so much weight and complexity it really seems better to build new.  That, however, is totally a subjective judgement on my part.  Your situation may differ.

Increase Trailer Width with Different MaterialsThis image shows one method to make a trailer wider done in wood.  In some ways it’s like the outriggers above, in other ways it’s sistering beams except the sisters are not there for added strength.  The sisters are there for attachment with the different types of material – which works.  (Note that a plywood deck over the top will significantly strengthen the added width.)

Adding material all along the perimeter gives additional rigidity to the eventual deck, and it also makes attaching things like sides much easier.  This technique of a perimeter piece all the way around has a lot of value, and it’s not exclusive to wood.  If you’re using metal for the frame, feel free to add a perimeter with something like the outriggers above.

This image shows adding width, and also adding length.  Making a trailer longer is the topic of this other article.

Make A Wider Trailer

Of course, there are other ways to make a wider trailer too, including combinations of the above.  This article is not all inclusive, but it should give some ideas.  Just make sure you choose the right material shapes as you build it wider.  Add gussets or overlaps as you re-join any cut beams.  Also, make sure you are very careful with alignments so the trailer tows well after.

Both of the approaches above (Outriggers and Split Width) have the nice advantage of ending up with a wider trailer.  To be more complete, they end up with a trailer having more square footage on the deck.  That means it will carry more volume, and it means it will carry wider objects.  However, it does not mean it will carry more weight.

Please note:  When you make a trailer wider, it will actually carry slightly less weight, because the process of widening adds material, and therefore increases the weight of the trailer frame.  Since capacity is the total weight (trailer plus cargo), if we make the frame 50 lbs heavier, we can carry 50 lbs less cargo.  (Those numbers might seem silly, but hopefully you get the point.)  To carry more weight, check out the article on increasing trailer load capacity.

Widening Disadvantages

The big disadvantage of either technique is the major tear-up to an existing trailer because there is a lot of additional welding and material in both cases.  The biggest potential challenge is the trailer will weight more, and won’t be as strong.  That’s not always the case, but something to think about.

In many cases, especially with the split width approach, the project to make a wider trailer is almost as big as building a new one.  So, before embarking on such a project make sure it is really as effective (cost / time / function) as you thought.  In many cases it seems like a good idea to begin with . . . but . . . after all the calculations, not so much.  Often it is best to sell that trailer, then build one that does what you want.

Trailer size is a big deal, and having the right trailer can make a big difference.  Anyway, if you wish to entertain building a trailer, check out the Trailer Plans Store.  We have a lot of different sizes and capacities.

Good Luck With Your Widening Project !!

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