Casita Travel Trailer Modifications – Bolt-on Shock Absorber Kit

The Backstory behind our development of the Bolt-on Shock Absorber Kit:

We have learned that the best product ideas come from our customers because that means we are solving a genuine problem that is causing problems for multiple people. But sometimes we need to be reminded of that. 

A year or so ago we got the first request for a bolt-on shock absorber kit. We mentally filed it away and soon forgot about it. Then a few months ago we got a spike in requests and realized that there was a real need for a solution. Other small travel trailers have shock absorbers on Torflex axles, so why don’t Casitas?  Once Dan got interested we were off and running.

Design Process:

Casita Trailer Axle Nuts

Casita Trailer Axle Nuts

The major problem to solve is to discover how much the trailing arm can move on the Dexter Torflex axle under all possible load conditions. The maximum “down” happens after you go over a big bump and with the trailer wheels off the ground the spring effect pushes the wheel down past its natural (no load) resting position. The maximum “up” is when a heavily loaded trailer hits a major bump at high speed while turning. Using data from Dexter for those extremes, we selected a shock absorber that could compress that distance plus a safety margin.  Then the CAD work began to design the actual mount plates. The lower mount point for the shock absorber is on the plate that is bolted to the back of the wheel hub. Next the work was completed on the upper mount plate that is bolted to the axle mount points.

The minor problem to solve is that all Casita trailers come out slightly differently. We call this the snowflake effect. So we have to allow some latitude in the placement of the body on the frame, and that is why we have to slot the holes that join the Axle Plate to the shock tower mount plate and a trim-able rubber bumper.


Shock Absorber Kit Wheel Mount Plate

Shock Absorber Kit Wheel Mount Plate

A prototype set was made by hand and bolted onto Dan’s Casita 17SD trailer, and a Go-Pro video camera was mounted underneath to record the findings. After a controlled drive around a test route, it became apparent that although the shocks were trying to work, a lot of the effort was wasted as the prototype mount brackets were flexing somewhat.

That was an easy problem to solve. Another set was made from heavier steel and gussets to reinforce the plates and keep everything rigid. The test was rerun and this time it worked great – actually better than we imagined. The result of this is the video you can find here (Note the significantly “beefier” brackets on the final version).

Dan then used the trailer for several long weekend trips and he always came back with a big smile on his face. He reported a much more stable tow and no more scattered contents on the inside. Others have since reinforced Dan’s finding and even reported lower tire temperatures. 

Could I Make these parts myself?:

Some Casita Club members with the correct machinery could, and indeed a few have. But our intent was to provide all the parts needed for the majority of members with basic mechanical abilities to be able to simply bolt it on. No design work, testing, procuring, laser cutting, bending welding, cleaning and powder coating.

Our solution takes some 70 individual parts and turns them into 3 major parts per side, plus of course those expensive Monroe Shock absorbers. The 3 major parts are called the axle mount plate, the wheel mount plate, and the shock tower mount plate.


The Install:

Removing Casita Wheel Hub Nuts

Removing Casita Wheel Hub Nuts

The install can be done with the wheels on and the trailer on the ground. It’s easier to do it on a hard floor than gravel. The first step is to fit the wheel mount plate. You need to remove the 4 nuts from the back of the wheel hub. Then simply mount the correct plate and re-tighten the nuts. The hardest part of the install is getting those big axle mount bolts to bust loose. You will need a long handled brake-over wrench for this. Once they are off you bolt on the axle mount plate with the new bolts supplied and torque them up. You then mount the top of the shock absorber to the shock tower mount plate and bolt the shock tower mount plate to the axle mount plate. The final step is to slightly compress the shock by hand and bolt the bottom of it into the wheel mount plate. Then repeat on the other side and you are done.

What We Learned:

Welded on axles have their mount plates further inboard than bolt-ons – That meant we had to make versions with longer tabs that rest under the frame for weld-ons.
Not all Casita bodies sit centrally on the frame – So some folks need to trim the rubber bumper on one side to make it fit.
Instructions have to be very clear – what seems obvious to us can be misinterpreted. One set got installed with the shock tower mount plates reversed which damaged the shocks. That is why we now color code the parts.
Casita owners are very patient and understanding as we work through these issues when they know that we are trying to do the right thing. That is why we like making things for Casita owners.

The End Result:

We are a bit biased but firmly believe that you will get less internal scattering of contents, less rivet-popping, less tire wear, better gas mileage and a much smoother ride. But don’t take our word for it, read the unsolicited testimonials over on our site,

Casita Shock Absorber Kit

Casita Shock Absorber Kit from Perfect Casita.

— This article was provided to The Casita Club by Orbital Machine Works