What Is Trailer Tongue Weight?

What is tongue weight? It is the downward force the trailer’s coupler puts on your hitch ball. Not the trailer’s total weight, just the part pressing straight down at the front.

It is one of the most important numbers in towing, and one of the least understood.

The number you want

For a bumper-pull trailer, tongue weight should be 10 to 15 percent of the total loaded trailer weight.

Loaded trailer weight means the trailer plus everything on it. So an 8,000 lb loaded trailer should put roughly 800 to 1,200 lbs down on the ball.

That range is not arbitrary. It is the window where the trailer tracks straight behind you without overloading the back of your truck.

What happens when it is too low

Under about 10 percent, the trailer starts to behave like a lever instead of a follower.

Any sideways push, a gust of wind, a passing semi, a lane change, starts the back end swinging. And here is the problem: that swing feeds itself. Each swing pushes the truck slightly, which pushes back, and the movement grows instead of settling.

That is trailer sway. It builds fast, usually at highway speed, and it is the most dangerous thing that happens to a bumper-pull trailer.

Low tongue weight almost always means the load is too far back. The fix is to move weight forward, not to drive more carefully.

What happens when it is too high

Above about 15 percent, you have a different problem.

All that weight sits on the very back of your truck. The rear suspension compresses, the back end squats, and the front end lifts.

When the front lifts, the front tires carry less weight. Your steering gets vague and your front brakes lose bite. Headlights point at the treetops. The truck feels floaty at exactly the moment you want it to feel planted.

High tongue weight also eats your truck’s payload, which is a separate limit you have to stay under.

Tongue weight comes out of payload, not tow rating

This is the part that surprises people.

Your tow rating limits how much the trailer can weigh. Your payload limits what sits in and on the truck. Tongue weight counts against payload.

Say you have a truck with 1,500 lbs of payload. You and a passenger are 400 lbs. Tools in the bed are 150. That leaves 950 lbs.

Now hook up a 10,000 lb loaded trailer. At 12 percent, that is 1,200 lbs of tongue weight. You are 250 lbs over payload, even though the trailer is well within your tow rating.

That is how people end up overloaded while thinking they have margin. Our post on whether your truck can safely tow walks through where to find both numbers.

How to control tongue weight

You control it by where you put the load, not by anything on the trailer itself.

The rule is about 60 percent of the load’s weight ahead of the axles. On a tandem-axle trailer, the balance point is the middle, between the two axles.

Move the load forward and tongue weight goes up. Move it back and tongue weight goes down. Small moves matter more than people expect, especially on a short deck.

Heavy end forward. On most tractors that means driving on nose first, since the engine and loader are up front. On most zero-turn mowers the engine is at the back, so backing on often balances better. Check which end of your machine is heavy.

Our post on distributing weight on a trailer goes deeper on placement.

How to check it without a scale

A proper tongue weight scale is the accurate way, but you can catch an obviously wrong setup by eye.

Watch the truck as you lower the trailer onto the ball. A little squat is normal. If the rear drops hard and the front visibly rises, tongue weight is too high.

Look at the trailer once it is hooked up. It should sit roughly level. Nose-high usually means the load is too far back.

Measure the fender gap. Before hooking up, measure from the ground to your truck’s rear fender lip. Measure again after. An inch or two of drop is normal. Three or more is worth investigating.

Trust the first mile. A correctly loaded trailer feels boring. If you feel any wander or side-to-side motion at 45 mph, pull over safely and move the load forward. Do not wait to see if it settles down.

If sway starts while you are driving

Do not brake hard. Do not steer against it. Both make it worse.

Ease off the accelerator and keep the wheel straight. If you have a brake controller, apply the trailer brakes only, using the manual lever. That pulls the trailer straight from behind.

Once you are stopped somewhere safe, fix the load before going any further.

The short version

Tongue weight is 10 to 15 percent of loaded trailer weight. Too little causes sway. Too much unloads your steering. You control it by putting about 60 percent of the load ahead of the axles.

Want help planning a specific load? Get in touch before pickup.

Serving Montevallo, Alabaster, Pelham, Calera, Helena, and the south Birmingham metro.