When building a tiny home on wheels there are several limitations you must adhere to if you do not want to go over the legal limit for road travel in the united states. These limitations are: Height, Width, Length and Weight. If you exceed any of these dimensions you will need to pull a Wide load or Oversized permit.
The Legal Limits as follows:
- Height: 13ft 6in in Most US States (Many West Coast States Allow up to 14ft)
- Width: 8ft 6in (9ft in Hawaii)
- Length: No vehicle combinations may exceed a total length of 65 feet in Most US States
- Weight: Varies by State, Number of Axles & Type of License Held by Driver, Average Weights are around 73,000lbs which is more than enough for any tiny house we have ever seen!
Today we are going to tackle the topic on vertical height and how some people choose to maximize the space in their tiny house by getting drop axles and the problems you may have if you choose drop axles for your tiny house trailer.
A Drop Axle is the axle of a vehicle or trailer that is bent upwards towards the ends, i.e. the center is ‘dropped’. This gives two advantages: the center gravity of the trailer is lowered relative to the wheels, which improves stability; Secondly by lowering the frame of the trailer you gain 4″ of vertical height inside your tiny house (in the lofts) which maximizes headroom since a loft is usually known as a space you will kneel and crawl into.
Quick Specs:
- 22″ Deck Height With Drop Axles. (14″ Fender Height Above Deck)
- 26″ Deck Height with Straight Axles (10″ Fender Height Above Deck)
The Problems
Road Clearance: When you lower the trailer with drop axles you bring the frame closer to the ground which increases the likelihood you will drag the tail end of the trailer going up very steep grades, Driveways or entering into gas stations. The longer the trailer, the more likely this will happen. Although dragging the rear of the trailer going up a driveway may not have any affect on the trailer itself since it is built with heavy duty steel, it may damage some components like plumbing lines “if” they are hanging down under the rear most part of the trailer. See below images that show the Clearance with and without drop axles.
With the trailer being closer to the ground, this also decreases the departure angle which is the maximum ramp angle from which the car can descend without damage. Approach and departure angles are also referred to as ramp angles. Approach and departure angles are indicators of off-road ability of the vehicle or trailer: they indicate how steep obstacles, such as rocks or logs, the vehicle or trailer can negotiate according to its body shape alone. When using drop axles, Utilities and fixtures should be above the departure angle line to aid in protection during travel.
Length: The longer the trailer, the more problematic drop axles may be when it comes to the above issues. When considering a trailer longer than 36ft for the lower deck, You may want to evaluate the building site you plan on towing to, the driveway you will enter as well as roads you plan on traveling often to see if these issues may affect you.
Is There Any Solutions?
If you feel drop axles may be too problematic for your tiny house build or the desired length of your trailer, they may not be the right fit for you. If after taking into account the previous mentioned problems and you see more advantages to drop axles over straight axles these are some solution you may want to consider.
Solution 1: Keep Waste lines for grey or black water as high up as possible and protected by the departure angle of the trailer. See image below
Solution 1b: Avoid have a sink, shower or drain near the tail of the trailer. If you can not avoid this, At least have this the high point in your plumbing so it can drain under the trailer towards the front where the plumbing will be more protected.
Solution 2: If you have drop axles already and you come to a driveway and its a bit steep, a easy fix is adding some DIY ramps. Pictured below is when we delivered a 28ft Entertaining Abode equipped with drop axles and the final parking spot had a very steep driveway. With some scrap wood and about 20 mins of time, This lifted up the trailer just enough to clear the driveway with no damage.
Strength Concerns
All Axles whether straight or dropped can handle the weight they are rated for. When choosing an axle rating for your build keep in mind the GVWR (Gross Vehicle Weight Rating) of the combined axles. This includes the weight they can handle including the weight of the trailer itself. For example, When you purchase a 24ft x 102″ wide trailer rated for 14k GVWR (which is 2-7k Axles) and you add the option of 4″ Drop Axles you will get upgraded to 2-7k Drop Axles to replace the straight axles. The warranty period from the axle manufacturer will be the same for straight axles and drop axles. When you are purchasing No matter the axle style you choose, Make sure to buy more “Trailer” than you think you need, because once your tiny house is built, you can not change the trailer.
Is There Is Any Advantages?
- Lower Deck height means lower center of gravity when moving, which is a big plus when a tiny house maxes out at the legal height of 13ft 6in from grade.
- The Lower Deck Height makes an easier approach or entrance into the Tiny House. This is beneficial so as to not have to step up so high and can save the knees quite a bit during the build hoping up and down the trailer deck.
- Drop Axles increase the interior space in your tiny house where it matters most, the lofts. Many people tend to bump their heads when sitting upright in their Loft, imagine what an extra 4″ of headroom will do?
Are Drop Axles Right For You?
With the information we shared above, We hope this helps you able to decide whether drop axles are right for you. There are advantages and disadvantages too. Please let us know you think!