Trailer Tongue Load Behind a Custom Pickup: Big Tex Single-Tire Manual

How do I account for trailer tongue load behind my custom pickup? Treat it as a hitch-load budget rather than a share of the trailer's total weight. Two different documents govern that budget, and they are usually kept in two different places.

Everything here is scoped to the Big Tex single-tire trailer manual, 2020 edition, for compatible single-tire models. That manual tells you how to load and check a compatible trailer; it does not rate your pickup, your receiver, your springs or your tires, so keep the trailer document and the truck's hitch documentation in the same folder and confirm the current manual for your exact model, axle and coupler.

What Tongue Load Really Measures on a Custom Pickup

Tongue load is the downward force the loaded trailer puts on the coupler, and it is never the trailer's whole weight. The trailer axles carry most of the total weight of the trailer and its contents, which Big Tex calls the Gross Vehicle Weight; whatever is left over is what the hitch carries.

Because the axles take the majority, the coupler only ever sees the remainder, which means the number you check at the hitch is smaller than the trailer's gross weight and has to be measured rather than assumed. It also moves every time you slide a heavy item across the deck.

The reason this catches modified trucks is that the hitch number lands on the rear of the pickup, on top of the bed contents, the passengers and whatever the rear axle is already carrying. One trailer load, two budgets to satisfy, and the trailer manual governs only one of them.

Why Both Low and High Tongue Load Hurt Stability

Low tongue load causes trailer sway. The reason the manual names both directions instead of one is that the coupler's downward load does two jobs at once: it holds the trailer tracking behind the tow vehicle, and it puts vertical weight on the rear of the truck, so a tongue weight that is too low degrades trailer sway stability while a tongue weight that is too high degrades tow vehicle handling, and no single setting improves both.

Pushing tongue weight up is not free either. The manual puts the high side in the tow-vehicle-handling column rather than the sway column, and the physical reason is that the added downward load sits behind the rear axle, which means less of the truck's weight rests on the front axle and the steering feels different; the two failure modes pull against each other, and the coupler setting that settles one makes the other worse.

Suppose a light tongue on a single-tire flatbed at highway speed: the trailer starts hunting side to side while the truck still feels steady, and the natural response is to steer against it. Now suppose the opposite, a tongue heavy enough to squat the rear of the truck: the trailer tracks straight, but the front end goes light and the driver works harder to hold a line. Both are load-distribution problems, and the manual files both under stability rather than handing out a percentage.

Build the Load From the Axles Forward, Not a Percentage

Start at the ceiling, not at a target. The total weight of the trailer and its contents must never exceed the trailer's Gross Vehicle Weight Rating, so the GVWR check comes before any tongue-load arithmetic, and it is read off the trailer's rating rather than judged by how the rig sits.

Then put the mass where the trailer can carry it. Towing stability depends on keeping the center of gravity as low as possible, which is why heavy items go on the floor and over the axles; the axles are the support point, so weight stacked high or hung past the ends is weight the coupler and the deck structure have to fight for the whole trip.

Even side-to-side distribution comes next. A trailer leaning to one side carries its load unevenly across the axle and the tires, and it will not track or brake like a level one. Only after the trailer is loaded low, over the axles and square do you check tongue weight, on level ground, with a tongue-weight scale.

Each step can be confirmed without a guess: the trailer's rating gives the ceiling, the deck shows whether the mass is low and centered, the tires show whether it is square, and the coupler gives one measured number instead of an impression. Because the hitch carries the remainder, that last check is a hitch-load check, not a trailer-weight check.

How to Measure Tongue Weight on Level Ground

To check the tongue weight, the tow vehicle and trailer must be on level ground, as they will be when the trailer is being towed. The reading is a setup measurement, so attitude is part of it: measure a rig sitting nose-high or nose-down and load has shifted between the trailer axles and the coupler, which means the number describes a rig you are not about to drive.

For lighter trailers, Big Tex recommends a tongue-weight scale, and if your dealer does not stock one the manual sends you to the company's support line instead. That is a measuring tool, not an adjusting tool: it reports what the coupler carries at that moment, with that load, at that attitude.

These pages do not spell out a scale-free method for the heavier single-tire models, so if your model sits outside the lighter range, the honest move is a documentation question to the manufacturer rather than an improvised measurement with hardware that was never meant for it.

Confirm the Setup With Three Checks Before You Tow

One: the loaded trailer sits inside the GVWR listed for that trailer, checked against the rating rather than against a memory of last season's load.

Two: the tongue reading was taken with the rig level and in its towing attitude, not on a sloped driveway that changes how the load sits.

Three: nothing in the setup matches either warning in the manual, so the trailer shows no low-tongue sway at towing speed, the truck shows no high-tongue handling trouble, and the rear of the tow vehicle is not overloaded. Big Tex calls the proper amount essential without publishing a universal figure, so confirmation is model-specific; if your manual does not give a target for your exact model, log that as an open documentation question rather than filling the gap yourself.

Where a Custom Pickup Changes the Tongue-Load Question

Suppose your pickup has had a rear suspension change, a lift, air bags or an aftermarket receiver. None of that is rated by the Big Tex manual. What the manual does say is that the remainder of the trailer's weight is carried by the tow vehicle hitch, which means the pickup's hitch rating, its rear-axle load and the condition of its mounting hardware sit in the same budget as the trailer's ceiling.

That is why a modified truck needs two documents side by side: the trailer manual for the trailer's GVWR and tongue requirement, and the pickup's hitch documentation for what the receiver is allowed to carry. Neither covers for the other. A suspension change that altered rear ride height also altered the attitude the loaded rig sits at, one more reason the level-ground rule is applied with the truck in its towing configuration rather than in whatever state it happens to be parked.

The Tradeoff Between Sway Control and Hitch Load

There is no direction that removes the tradeoff, only a position between the two failures. Because both warnings sit on the same coupler setting, the useful question is not whether to add tongue weight but how much this trailer and this hitch will take.

Big Tex gives no percentage and no numeric window in these passages, which means the correct value is a setup question about your trailer model and your hitch, not about trailers in general.

For a fleet, this shows up as two identical trailers behind two differently configured pickups needing different loading, because the hitch side of the budget differs even when the trailer side matches exactly.

Here is what you can do today. Park the rig on level ground, pull your model's trailer manual and the pickup's hitch documentation, and either set a tongue-weight scale under the coupler or call Big Tex at (903) 575-0300 if your dealer cannot supply one. Write down two numbers: the trailer's GVWR and the load the hitch is actually carrying. Tow on those, not on a figure inherited from someone else's trailer.