Reasonable ground clearance for rough roads??

[myoung]

Rough roads in places like National Forest dirt roads, washboard surfaces, BLM roads. Not "off-roading."

I just want to have enough ground clearance under my TTT so that I can take it to out-of-the-way places for photography, fishing, and camping. The critical point, I believe, is under the rear bumper where, with the Dexter #9 axle at zero degrees orientation and 13-inch tires, the ground clearance is approximately 9 inches.

I have the possibility of getting a Dexter #9 with 10 degrees of upward orientation, which would lower the ground clearance to 8 inches and give me another inch to add to the interior ceiling height.

So, the question is: Is it safe and prudent to go with the 10-degree upward orientation and have an 8-inch ground clearance at the rear for the kind of road travel I've described?

In thinking about the problem, I set up a simple seesaw diagram where the distance from the rear bumper to the hitch ball is 174 inches and the fulcrum, the position of the axle is 69 inches from the rear. Ignoring the slight differences due to arcs about the fulcrum, each inch of upward displacement at the hitch ball would reduce the ground clearance at the bumper by 0.657 inches.

So, with 9 inches of clearance, the hitch ball would have to rise 13.7 inches before the bumper would scrape the ground. Alternatively, using the upwardly angled axle adjustment, with 8 inches of clearance, the hitch ball would have to rise 12.2 inches before scraping.

It seems to me that 12 inches of upward bump at the hitch ball is way beyond reason on even the bumpiest of roads so it would seem okay to go with the lower-height axle.

What do those of you with infinitely more experience with this subject than I think?

Thanks in advance for your guidance.

[jss06]

I would be more worried with any ditch crossings where you drop the trailer axle into a hole. Don't forget about rutted roads where you may high center as well. I would stay at 9 inches to be safe.

I have been in some campgrounds where you would have problems even at that height.

[myoung]

I would be more worried with any ditch crossings where you drop the trailer axle into a hole. Don't forget about rutted roads where you may high center as well. I would stay at 9 inches to be safe.

I have been in some campgrounds where you would have problems even at that height.

Good point about ditches. The only time the bumper of our Airstream ever scraped was crossing a deep stream bed in a CA State Park. I think it was a combination of the wheels (twin-axle) in the stream and the Dodge pitched up and then down over a large hump in the road on the far side of the stream. That really jacked up the hitch.

[myoung]

my teardrop is 20 inches from the bottom of the frame to the ground. I can back it up over any hump with out bottoming out. slowcowboy.

Okay. So, 20 inches is a safe clearance, although I wonder if that is the real clearance because the axle might be lower and your tow vehicle most likely has less clearance.

The question I posed, perhaps not clearly, was what is the lowest possible clearance for the types of surfaces I described? Or, more precisely, could I get away with 8 inches rather than the 9 that I already have designed in?

[aggie79]

Mike,

My comments are based on "looks" rather than actual experience, so please keep that in mind.

I have a Dexter with a 10 degree up angle. My tires are 235-70R15s. Loaded - weight of teadrop - this combination gives me 12" of clearance at the bottom of the frame rails. I do have stabilizers at the rear that are "tucked up" in the frame rails but still hang down about another 2" making the clearance about 10". Up front, my a-frame tongue is below my frame rails which makes the clearance on it 10" also.

On level roads, my eyeball assessment is that everything would be okay for some pretty rough, but not off-road, roads. I am concerned about entry and exit over dips, bar ditches, etc.

With the greater rear overhang of the Compact design, I would probably recommend a 2 inches or so higher ground clearance than what I have.

[myoung]

I have a Dexter with a 10 degree up angle. My tires are 235-70R15s. Loaded - weight of teadrop - this combination gives me 12" of clearance at the bottom of the frame rails. I do have stabilizers at the rear that are "tucked up" in the frame rails but still hang down about another 2" making the clearance about 10". Up front, my a-frame tongue is below my frame rails which makes the clearance on it 10" also.

On level roads, my eyeball assessment is that everything would be okay for some pretty rough, but not off-road, roads. I am concerned about entry and exit over dips, bar ditches, etc.

With the greater rear overhang of the Compact design, I would probably recommend a 2 inches or so higher ground clearance than what I have.

Quite a few folks have the larger 15-inch tires. Mine are the smaller but sufficiently capable 13-inch tires. I'll leave room to go with larger tires in the future if necessary or desirable.

I'm going to order my Dexter #9 tomorrow and given all the solid input from people and reading more on other threads, I'm going to stick with the zero degree setting and the 14-nominal height to the top of the frame longitudinals.

[dh]

...which would lower the ground clearance to 8 inches and give me another inch to add to the interior ceiling height.

I must have missed something, how does lowering your ground clearance an inch give you another inch of celing height?

[jss06]

...which would lower the ground clearance to 8 inches and give me another inch to add to the interior ceiling height.

I must have missed something, how does lowering your ground clearance an inch give you another inch of celing height?

He can lower the frame height by one inch then he can raise the cabin height by one inch and still get it into the garage.

[dh]

...which would lower the ground clearance to 8 inches and give me another inch to add to the interior ceiling height.

I must have missed something, how does lowering your ground clearance an inch give you another inch of celing height?

He can lower the frame height by one inch then he can raise the cabin height by one inch and still get it into the garage.

I guess I missed the TTT part. That makes sence now.

[Cliffmeister2000]

Isn't the length of the trailer a critical part of the ground clearance discussion? I've had to move my licence plate, because it was constantly being dragged when leaving the driveway. Even though my TV (a Nissan Frontier) sits pretty high, I've had the hitch get pretty close when going across a steep dip in the road. It would seem that the longer the trailer, the greater risk involved in bottoming out??

[aggie79]

Isn't the length of the trailer a critical part of the ground clearance discussion? I've had to move my licence plate, because it was constantly being dragged when leaving the driveway. Even though my TV (a Nissan Frontier) sits pretty high, I've had the hitch get pretty close when going across a steep dip in the road. It would seem that the longer the trailer, the greater risk involved in bottoming out??

Cliff,

I think you are spot on. I am more concerned about the hitch dragging than the rear of my teardrop.

I think offroaders are concerned about the overhang - the length of body/chassis that extends beyond the axles - in addition to ground clearance.

Tom