If you’ve spent any time researching towing, you’ve heard the rule:
“Keep tongue weight between 10–15%.”
It’s good advice. But it’s incomplete.
Many RV owners assume that if their tongue weight is correct, sway shouldn’t happen. Yet properly loaded trailers still experience instability every day.
Why?
Because trailer center of mass and tongue weight stability are only part of the equation.
To truly understand towing balance physics, we have to go deeper.
The center of mass (COM) is the point where the trailer’s weight is evenly distributed in all directions.
In a travel trailer, it shifts depending on:
When the center of mass moves rearward, tongue weight decreases.
When it moves forward, tongue weight increases.
This is why loading affects stability.
But center of mass alone does not determine sway behavior.
Proper tongue weight:
However, tongue weight is a static measurement.
Sway is a dynamic event.
You can have perfect 12–13% tongue weight and still experience sway under:
Why? Because rotation still occurs at the hitch ball.
This is where most discussions stop short.
In motion, aerodynamic forces act on the center of pressure (COP)—not the center of mass.
The center of pressure is the average location where wind forces push against the trailer’s side surface.
In most travel trailers:
When crosswinds hit:
This torque creates yaw—regardless of correct tongue weight.
That’s the missing piece in most towing balance physics discussions.
To understand sway, imagine this simplified system:
Even with proper loading, that torque exists.
Tongue weight increases resistance to instability—but it does not eliminate the pivot point itself.
As long as the pivot allows rotation, external forces can create yaw.
Here’s the critical takeaway:
Loading reduces instability risk.
It does not remove the mechanical condition that allows instability.
If the trailer can pivot freely at the ball:
Even perfectly balanced trailers remain vulnerable to dynamic forces.
That’s why so many owners say:
“I’m within all my limits—why is this still happening?”
Because limits manage weight, not geometry.
Another overlooked factor is dynamic load transfer.
Under acceleration or braking:
Under crosswinds:
These transient shifts can reduce effective stability—even if static measurements are correct.
This is why trailer loading safety is essential—but incomplete.
Many assume upgrading the tow vehicle fixes instability.
While heavier trucks reduce sensitivity, they do not eliminate:
Stability improves, but the underlying geometry remains unchanged.
The only way to remove rotational instability entirely is to change the pivot location.
The ProPride 3P® Hitch uses Pivot Point Projection™ to relocate the effective pivot point forward near the tow vehicle’s rear axle.
This eliminates the independent rotation of the trailer at the ball.
When lateral force acts:
Loading still matters—but it is no longer your only defense.
Correct tongue weight is essential.
Balanced cargo is critical.
Understanding center of mass is important.
But those factors manage weight distribution—not rotational freedom.
True stability requires:
Without geometry control, sway remains possible—even if unlikely under ideal conditions.
The common 10–15% tongue weight rule is a starting point—not a solution.
Trailer stability depends on:
Loading improves balance.
Geometry determines whether yaw can occur.
And as long as the trailer can pivot freely at the hitch ball, dynamic forces can create instability.
That’s why proper loading is necessary—but not sufficient.
True sway elimination requires eliminating the pivot that allows it.