How Much Clearance Is Needed Between Truck Bed And Fifth Wheel
Minimum clearance between truck and fifth wheel must be 6″
Lower than 6″ may cause a direct impact or at least the underside of the overhand or gooseneck rub the bed rails, the bed walls, or the tailgate, depending on the truck.
More than 10″, may lift up the nose of the fifth wheel too much, can cause trailer sway, more pressure on the rear tires of the trailer, and rear axle, cause a lower trailer hitch weight and can cause chucking on the hitch due to the differential forces between the truck and the RV.
An inch more or an inch lesswill not make a significant difference in the weight carried on the axles. There is an “equalizer” mounted between the springs, rear of the front spring and front of the rear spring. The purpose of the equalizer is to equalize the weights and stresses between both axles.
Thus, if you raise the front of your fifth wheel an inch, it should put a touch more weight onto the rear axle of the trailer. Here comes the equalizer that will balance that weight shift caused by a “nose high trailer pin” by shifting or equalizing the weight between the two axles.
Equalizers are suspended from the center hanger and serve as a link between leaf springs on multi-axle trailers. Equalizers transfer weight from one axle to another, specifically when you drive over a bump, but it can happen in any situation.
5th wheel pin boxes can usually be moved up or down a set of holes which could give you 2″ or more easily either way. The 5th hitch also has vertical adjustments if these are needed.
Height Range To Choose
5th wheel hitches vary in their height range. You can select a hitch with a higher maximum height setting to provide clearance at the bed rails, but this will also require adjusting the position of the trailer pin box on its mounting wings, and also possibly lifting the trailer suspension with an over-under kit like the Dexter Trailer Springs Over-Under Conversion Kit
The hitched trailer must be level. Lifting the trailer helps with leveling but it does raise the trailer’s center of gravity, which tends to degrade handling by allowing more side-to-side motion.
With the trailer level, your ground-to-overhang distance should be no less than 5-inches more than your ground-to-bed rail distance.
Criteria For Choosing Hitches
So a question here is if there is an RV industry-standard (RVIA) fifth wheel coupler height range so we can purchase a suitable product to handle a proper fifth wheel hitch height from ground that later serves us to obtain an adequate proper clearance of at least 6″ between the underside of the gooseneck and the bed rails of the truck.
The answer is no. If an RV owner has a flatbed, then he has a blank slate as to what 5th wheel hitch to purchase. The hitches on the market have a variety of height ranges.
I can say that the decision depends on the fifth wheel you have.
But what if you do not have the fifth wheel yet? What if I want to have the truck ready to tow and decide later on for the fifth wheel and the hitch? What if I say, “well, I have this nice towing vehicle, this truck, so now I want to know which fifth-wheel and which hitches are available.
I want that these fifth-wheel hitches are easy to mount and adjustable. Reese sells various rail mounted and puck mounted fiver hitches, too numerous to inventory here, but Reese also sells a 30K low profile fiver hitch with a range between 9 and 12 inches off the deck.
The most precise example is offered by Pullrite, who makes many different 5th wheel hitches and I will only concentrate on just one model of hitch that they sell, their highest capacity 25.5K non-gliding Super 5th.
Of this one hitch, Pullrite makes four different versions. Two are of fixed heights, one shorter and one taller. And not one, but two others are height adjustable.: the model 0504 ranging from 15.5 to 18.5 inches, and the model 0515 ranging from 11.5 to 13.5 inches.
For example, Hensley sells a low profile Binkley head on a plate, as well as a mid profile TSLB2H that is bolt mounted, as well as a higher profile BD3 that is rail mounted.
A flatbed also affords a blank slate as to how that whatever hitch chosen will be installed, which can affect the starting and ending point of the range of adjustability afforded by the hitch itself.
Whether the hitch is rail, puck, J pin, or L plate surface bolted, there is still a choice to mount the connection to the truck above or below the deck surface of the flatbed, and depending on the depth of the channels that make up the flatbed, and the distance of the bed from above the frame rails, there is great variability.
Knowing the average industry standard to expect most RV’s to fall within is a useful data point to make some of these decisions with.
There is less room for choice with pickup trucks than flatbeds. Making a hitch selection and deciding on an installation method that optimizes the range of variability within the hitch itself and in most pin boxes does take some forethought.
Ensure that you have enough clearance at tailgate and bedside. Keep in mind steep driveways or side roads. The more lift you have the more wind and bow wave from large rigs will affect the stability. You will also have less stability in corners.
If the trailer is being towed nose up, the hitch weight will be too low and can lead to riding problems with the truck, bad trailer sway, and tracking problems with the trailer. If it is too low it can weigh the rear of the truck down and cause the front to raise up and lead to handling and braking problems and the trailer could also sway since less weight will be on the axles.
You will want the hitch to be set at the height that 1) allows the trailer to be level, and 2) allows you a minimum of 6 inches between the bottom of the trailer loft and the top of the bed rails. The fifth wheel hitches offer several inches of up and down adjustment to help accomplish this. Many pin boxes are also height adjustable.
To do this you will want to measure from the top of your truck bed floor to the ground and then measure from the plate of the pin box on the trailer down to the ground when the trailer is level on level ground. The difference between these two measurements is the correct hitch height you would need.
The Curt A16 5th Wheel Trailer Hitch w/ R16 Slider – Dual Jaw – 16,000 lbs is adjustable from 17-1/2″ – 21-1/2″ and the Curt E16 5th Wheel Trailer Hitch w/ R16 Roller – Slide Bar Jaw – 16,000 lbs is adjustable from 15 to 17″.