I just made a post to the Casita
Forum regarding ground clearance and know it will be of interest to some of us.
I am in the middle of having a second axle
For the faint of heart, the failure of the first axle
was MY fault for not checking the bearings before I set out for a long trip when it had been sitting in one place for a year. Living in it does not mean water can't penetrate the seals and contaminate the grease. The current axle
was ordered incorrectly (missing brake flanges, didn't have EZLube and was Low Profile rather than High Profile).
There are several ways to raise the body of the trailer. The first is to order Dexter's High Profile axle rather than the Low Profile, which refers to the bracket, an integral part of the axle assembly. On my '91 Scamp
13, the high profile bracket was the norm; I dunno about other models or brands -- the difference between the two is only 0.88", but that's almost an extra inch of clearance between the tire and top of wheel well.
The next way to get some height is to have a spacer welded between the trailer frame and the axle bracket; I believe Casita
uses a 2" spacer and Scamp
doesn't offer a spacer at all (not at all certain about some of this as things are subject to change).
Obviously, both of the above are things best done when the trailer is ordered, altho an axle shop could cut off your axle, insert a spacer, and weld axle to spacer and spacer to frame. In total, these two options will raise the body 2.88" above the axle, BUT the ground clearance of the axle and running gear will NOT change, as all you have done is raise the frame and body. Also, you will have to adjust your hitch ball height to keep the trailer level. NOTE: Off level or side-to-side imbalance affects axle loading, wheel toe-in and road handling in general.
A third way to raise the frame/body is to specify a larger upper load range on the axle when it is originally ordered. Dexter will build the axle with more rubber cords, making it stiffer. However, more is not always better; a stiffer ride will result in more vibration, closet doors opening, rivets popping, frame flexing, stress on frame welds, stress on doorway opening, etc. (If you have ever pulled a boat trailer for a heavy boat without the boat on top, you will know exactly what I mean. If you get too much stiffness, the only way I can think of to ease the ride and resultant damage would be to run with your tire pressures on the low end or use tires
with lower sidewall ratings.
If you are really serious about getting ground clearance, the next step, having raised the frame/body with respect to the axle stuf, which gives you clearance between the tire top and wheel well, you now replace your existing rims and tires
with the next size up. The effect of this is to actually raise everything by the radius difference of the orig rim/tire and the new rim/tire.
Why do all this? The two big advantages to raising the trailer are to get a lot of ground clearance and to bring the trailer bottom level with the truck bottom (or at least more level). Ground clearance is obvious; less dragging of tail on steep driveways and rough (or no) road conditions. Having a level with the truck means that the trailer isn't creating an "air dam" between the truck and trailer, altho this is partially offset by the increase frontal area above the truck. I raised a 16' Jayco and a friend raised his 26' Avion; we both got towing improvement with regard to wind resistance.
What are the drawbacks? For the rapid drivers, the better air profile is a good thing, but the resultant higher center of gravity is a bad thing. Because the COG is higner, the trailer is more likely to rock side-to-side from air currents, road roughness and steering input. When it rocks, weight
transfers between wheels, changing suspension and tire geometry and causing "dog-tracking", all of which will negatively affect handling and mileage.
Effectively, when you raise the COG, you are going from an automobile configuration to an SUV configuration. Just like the SUV, a trailer with a high COG is more likely to actually roll over than one with a low COG. Options high up, like power fans and roof air conditioners make things worse, of course. If you should decide to have a raised trailer, you must be very careful about packing your heavy stuf, like canned goods and even clothing, low. (It's surprising how much stuf like clothing and bedding can weigh in total).
Pete and the RatLadies who adjust their ground clearance and COG on the fly to suit conditions