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Theoretical heights.

MatthewThomas
Explorer
Explorer
I was looking up the legal DOT heights (13.5ft) as well as the minimum recommended clearance between truck and bottom of the 5th wheel overhang (6in) then crossed it with the most recent height measurements for Ford trucks (no bias, just the first one I could find).

They don't have a direct measurement to the top of the bed but they had a measurement from open tailgate to ground 36.9in (F350 biggest wheelbase) then a height from the bottom of the bed to the top 21.1in, totaling 58in.

Adding the 6in for bed clearance - 64in.

Now take the federal max height 13.5ft (162in), and minus 2in (personal choice for peace of mind) which leaves 160in.

Minus the 64in and that leaves you with 96in or 8ft.

My question is, if you take off an extra foot for insulation and structuring (would be a bit excessive but using it for a more conservative outlook), could the interior of the overhang portion of the 5th wheel be 7ft?
30 REPLIES 30

MatthewThomas wrote:
MNRon wrote:
There's usually an AC on top of that roof that you haven't accounted for


Possibly. We were looking at a minisplit instead to go on a side or something.


There are width restrictions as well... IF you are going to put a MINI split on the side, that will also take up much needed living width space....

Wouldn't it be easier, and safer to buy a totaled out/salvage unit and rebuild it from ground up? At least you would have the BONES/structure already to work with...
Me-Her-the kids
2020 Ford F350 SD 6.7
2020 Redwood 3991RD Garnet

valhalla360
Nomad
Nomad
TXiceman wrote:
One time we had an oversize load hit a bridge (it was over height, width, length and weight). It was winter, so we had to watch the axle load limits on certain roads coming from Toronto to the Texas Gulf Coast. The driver decided to get off his designated route and visit a girlfriend and found a bridge he would not fit under. It cost his insurance and trucking company about $350,000 for repairs on the equipment in 1977. The trucking company said he would never drive again in North America.


On the positive side, when an RV meets a bridge beam, it's just a matter of sweeping up the RV pieces and maybe a little paint to touch up the steel beams.

Now a big excavator with the arm up too high...that insurance company got to buy a new bridge as he was well into the 3rd beam before the arm ripped off. Even worse, it was put an expedited schedule because the freeway was being shut down. I was only involved in the traffic control for the response but I'm sure it was several million before it was all done.

Stay within 13.5 (13ft 6inch, etc...) and it's generally not a big issue. The rare bridges that are below that are typically heavily signed.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

TXiceman
Explorer
Explorer
I designed large packaged systems that we had to design with the transport means in mind and where it was headed. The shipping department handled all the logistics with the truckers. Before a loaded truck left the shop, we had the driver up top with a tape measure and to also check maximum with and overall length. We noted these dimensions on the way-bill so that he was fully aware of his load size.

One time we had an oversize load hit a bridge (it was over height, width, length and weight). It was winter, so we had to watch the axle load limits on certain roads coming from Toronto to the Texas Gulf Coast. The driver decided to get off his designated route and visit a girlfriend and found a bridge he would not fit under. It cost his insurance and trucking company about $350,000 for repairs on the equipment in 1977. The trucking company said he would never drive again in North America.

So, measure your rig yourself and watch the low clearances.

Ken
Amateur Radio Operator.
2023 Cougar 22MLS, toted with a 2022, F150, 3.5L EcoBoost, Crewcab, Max Tow, FORMER Full Time RVer. Travel with a standard schnauzer and a Timneh African Gray parrot

msmith1_wa
Explorer
Explorer
TXiceman wrote:
Well, let's confuse the matter a bit more for the math challenged...

13.5 feet = 13 feet-6 inches = 4.1148 meters = 411.48 centimeters.

In either case, over this height does require an over height permit for travel. There are also legal limits, for width, length and weight before you will be required to have a travel permit and sometimes an escort service.

Enjoy the day folks.

Ken


The threshold for needing an oversize load permit depends on the state you are in. Only looking at the height allowed. There are quite a few that allow 14ft and a couple that allow more, without a permit. Looks like Alaska allows 15ft.
2003 Silverado 2500HD 4x4 8.1l
2016 Evergreen Amped 28FS

TXiceman
Explorer
Explorer
Well, let's confuse the matter a bit more for the math challenged...

13.5 feet = 13 feet-6 inches = 4.1148 meters = 411.48 centimeters.

In either case, over this height does require an over height permit for travel. There are also legal limits, for width, length and weight before you will be required to have a travel permit and sometimes an escort service.

Enjoy the day folks.

Ken
Amateur Radio Operator.
2023 Cougar 22MLS, toted with a 2022, F150, 3.5L EcoBoost, Crewcab, Max Tow, FORMER Full Time RVer. Travel with a standard schnauzer and a Timneh African Gray parrot

MatthewThomas
Explorer
Explorer
msmith1.wa wrote:
Some reading material regarding vertical clearance and max vehicle height.

FHWA vertical clearance


RVIA

Heavyhaul.net





Interesting literature. Even tells about permits and such if necessary. I really appreciate it!

MatthewThomas
Explorer
Explorer
jaycocamprs wrote:
MatthewThomas wrote:

Unnecessary, but this is theoretical, I don't have a unit, but am planning a build and want to know if my theoretical numbers make sense.


If you thinking of building a trailer, you need to look at this thread. BoonHauler BoonHauler was a member here but hasn't posted in years. From what I remember reading the build thread he really did it right. Took a good while but really looked good when he was done.


Hey thanks for the material I'll definitely be giving it a look.

MatthewThomas
Explorer
Explorer
way2roll wrote:
Thanks for the clarity. Keep us posted on your build. Never seen anyone build up a FW. Pretty interesting project.

I still think there is a ton of value in measuring real world units. Lots of engineers over decades have refined the design of current FW's.


Definitely will. The next time I go into town I plan on taking a measuring tape with me.

msmith1_wa
Explorer
Explorer
Some reading material regarding vertical clearance and max vehicle height.

FHWA vertical clearance


RVIA

Heavyhaul.net
2003 Silverado 2500HD 4x4 8.1l
2016 Evergreen Amped 28FS

jaycocamprs
Explorer
Explorer
MatthewThomas wrote:

Unnecessary, but this is theoretical, I don't have a unit, but am planning a build and want to know if my theoretical numbers make sense.


If you thinking of building a trailer, you need to look at this thread. BoonHauler BoonHauler was a member here but hasn't posted in years. From what I remember reading the build thread he really did it right. Took a good while but really looked good when he was done.
2018 Silverado 3500 DRW
2011 Montana Mountaineer 285RLD

Allworth
Explorer
Explorer
The Traffic Engineering Department agrees with Yahalla!!
Formerly posting as "littleblackdog"
Martha, Allen, & Blackjack
2006 Chevy 3500 D/A LB SRW, RVND 7710
Previously: 2008 Titanium 30E35SA. Currently no trailer due to age & mobility problems. Very sad!
"Real Jeeps have round headlights"

valhalla360
Nomad
Nomad
I wasn't correcting his units. Never had an issue with 13.5ft vs 13'6". That was you.

I was correcting his statement that 13.5ft is the minimum height for bridges and that there is not a height limit on trucks It may not be called a "DOT height" but that's semantics...over 13.5ft and you can expect to pull permits if you want to be legal.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

Wadcutter
Explorer III
Explorer III
Let me refresh your memory then on what you wrote to Second Chance who said 13'6" was the legal height. You took issue with his post stating someone had informed him wrong. Here's what you wrote:
"You had someone inform you wrong.
13.5ft is the maximum height before you are considered an oversize load that requires permits for each trip."
So now you're saying Second Chance wasn't wrong? Apparently so after you understood the conversion of 13.5 to 13'6".
Obviously when you were so quick to tell Second Chance he was wrong about 13'6" that you weren't doing your math and realize that 13.5' is exactly what Second Chance said at 13'6". Second Chance wasn't told wrong by anyone. His post was correct. It's you who couldn't understand the conversion and then was so quick to jump on him.
As far as what is "limiting because once you get off the roads and into RV parks, no guarantee you will have even 13.5ft." is a bogus argument and has nothing to do with legal height. Once you get on private property like an RV park there's no telling what over hanging objects will be encountered. But that has nothing to do with the discussion of what is legal.
Camped in every state

valhalla360
Nomad
Nomad
Wadcutter wrote:
valhalla360 wrote:
Second Chance wrote:
Someone with a CDL and experience straightened me out on this on another forum recently. There is no such thing as a legal "DOT height" from the Federal government. 13'6" is the minimum height for overpasses on the interstate highway system. Some states have their own regulations. That said, there is no such thing in my books as a "theoretical height." The only thing you can rely on is an actual measurement with the trailer on the truck on level ground.

Rob


You had someone inform you wrong.

13.5ft is the maximum height before you are considered an oversize load that requires permits for each trip.

Sounds like someone informed you wrong. Second Chance is correct at 13'6".
Probably what you read is max height of 13.5'. That's 13 and 1/2 foot. 1/2 foot is 6", not 5".
13'6" is the max legal height without a permit. Anything over 13'6" requires a permit. .............


13ft 6in is the same as 13.5ft, which is what I wrote.

Even 13fyt 5in is going to be limiting because once you get off the roads and into RV parks, no guarantee you will have even 13.5ft.

I used to issue permits for a state DOT. I also do signing and design exception reviews...which includes bridge heights.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

Wadcutter
Explorer III
Explorer III
valhalla360 wrote:
Second Chance wrote:
Someone with a CDL and experience straightened me out on this on another forum recently. There is no such thing as a legal "DOT height" from the Federal government. 13'6" is the minimum height for overpasses on the interstate highway system. Some states have their own regulations. That said, there is no such thing in my books as a "theoretical height." The only thing you can rely on is an actual measurement with the trailer on the truck on level ground.

Rob


You had someone inform you wrong.

13.5ft is the maximum height before you are considered an oversize load that requires permits for each trip.

Sounds like someone informed you wrong. Second Chance is correct at 13'6".
Probably what you read is max height of 13.5'. That's 13 and 1/2 foot. 1/2 foot is 6", not 5".
13'6" is the max legal height without a permit. Anything over 13'6" requires a permit. Some states go with max legal at 14' only on specific routes.
No one wants to get a permit for overheight 5ers. When you get a permit the permit will specify the exact route you are restricted to travel. Absolutely no deviation from the route listed on that permit or the permit is not valid. No deviation. Not even to pull off to get fuel.
You must stay exactly where the permit allows. The permit will also specify the days and time of travel. Every time you travel you would be required to get a new permit for that specific trip. Depending on the height a permit may require a lead escort vehicle with a height stick.
Life gets a WHOLE lot more complicated for permit moves.
I did truck enforcement and dealt with oversize loads for 42 years, taught truck law, taught motor carrier safety law, and was recognized by the courts both state and federal as an expert in truck laws.
Camped in every state