Trailer Sway & Sway Control
Car Trailer Sway Control, and Which Way to Load the Car
A car hauler carries one enormous item you can position two ways. That single choice outweighs every piece of hardware on the market.
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Short answer
On a car trailer, load the vehicle engine-first - nose toward the tow vehicle - in nearly every case. The engine is the heaviest part of a car, and putting it ahead of the trailer's axles is what produces the tongue weight that keeps the trailer stable. Loading a front-engined car backwards is the most common cause of car hauler sway.
What makes a car hauler different from every other trailer is that the load is a single object weighing more than the trailer itself, and you get to choose which way round it faces. That decision moves hundreds of pounds between the front and the rear of the trailer in one go. No sway bar, cam or friction pad on the market has that much authority over the outcome.
Which way round, and why
Most cars carry well over half their weight on the front axle, because that is where the engine and transmission sit. Drive a front-engined car up the ramps nose-first and that mass lands ahead of the trailer's axles, pressing the tongue down. Drive it on backwards and the same mass lands behind the axles, lifting the tongue and turning the whole load into a pendulum.
| Vehicle | Load it | Why |
|---|---|---|
| Front-engined car or crossover | Nose first, toward the tow vehicle | Puts the heavy end ahead of the trailer axles |
| Mid or rear-engined car | Usually tail first | The heavy end still needs to be forward on the trailer |
| Non-running vehicle, engine removed | Measure, then decide | The weight distribution is no longer the factory one |
| Two motorcycles or light machines | Split the weight either side of the axle, biased forward | Several small items give you finer control than one car does |
The principle is that the heaviest part of the load belongs ahead of the trailer's axles. The vehicle's engine position is the quickest proxy for where that mass is.
Verify it rather than trusting the ramps
- Load the car, chock the trailer and strap down. Do not measure anything while the trailer can move.
- Measure the tongue weight. The lever method with a bathroom scale works, and a tongue weight scale is faster if you do this often.
- Compare it with 10 to 15 percent of the loaded trailer weight. Trailer tare plus vehicle weight is the figure to take the percentage of.
- Adjust by moving the car, not by adding hardware. Six inches of fore and aft position on a 3,500 lb car changes the tongue weight substantially.
- Check the tow vehicle's stance. If the rear squats and the front rises, you have either too much tongue weight or a vehicle that needs load transfer.
The things that make a car hauler worse
- A long trailer with a rear ramp assembly. Ramps, a beavertail and a rear gate are permanent weight behind the axles. That is fine loaded and noticeable empty.
- Straps that let the car move. Four-point tie-downs at the wheels rather than the body let the suspension work and keep the car where you put it. A car that creeps rearward has changed your tongue weight mid-trip.
- Open-deck wind load. A car on an open trailer is a large, bluff object. Passing trucks and crosswinds push it, and the longer the trailer the further behind the axles they push.
- Brakes on only one axle, or none. A tandem car hauler carries real weight, and under-braked trailers encourage the tow vehicle to do work that upsets the rig. Whether you need a controller is partly a legal question.
Which hardware actually helps
1. Start here
Sherline Trailer Tongue Weight Scale
Sherline · Best for measuring tongue weight at home
A dedicated scale you sit under the coupler to read tongue weight directly, with no arithmetic and no trip to a weighbridge. It is the one tool on this site that turns the single most important towing number from a guess into a measurement.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Direct reading, with no bathroom-scale-and-lever arithmetic
- Repeatable, so you can see what moving the load actually does
- Mechanical gauge with no batteries to be flat when you need it
What does not
- Must be used on level ground with the coupler at towing height
- Single-purpose tool that spends most of its life in a cupboard
Skip it if
Unnecessary if your hitch already has a built-in gauge, or if you have a public scale nearby and are happy to use it.
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Raw specifications: Sherline’s own page. We earn nothing on that link.
2. Best first hardware
CURT Sway Control Kit
CURT · Best for light trailers that wander
A single friction bar between the trailer tongue and the ball mount, with adjustable tension. It damps yaw; it does not transfer load. On a light trailer that wanders a little it is the cheapest honest fix, and on a heavy one it is not enough on its own.
What works
- Simple, serviceable and easy to fit to an existing ball mount
- Tension is adjustable, so you can match it to the trailer
- Takes minutes to add to a setup you already own
What does not
- Must be disconnected before backing up tightly or in icy conditions
- Damps sway but does nothing about a tow vehicle that is squatting
Skip it if
The wrong answer if your truck sags at the back when the trailer is on - that is a load-distribution problem and a friction bar will not touch it.
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Raw specifications: CURT’s own page. We earn nothing on that link.
3. If the tongue weight is high
Reese Strait-Line Weight Distribution Hitch with Dual Cam Sway Control
Reese · Best for long trailers in crosswinds
Dual-cam sway control works differently from friction: the cams hold the trailer in the straight-ahead position and have to be pushed out of it, then they pull it back. That is a restoring force rather than a damping one, and it is the reason people who tow long trailers in crosswinds keep choosing it.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Cams actively return the trailer to center instead of only resisting movement
- Performance does not fall off when the friction surfaces get wet
- Well-understood system with decades of setup documentation behind it
What does not
- More parts to position correctly at setup than a single-friction system
- Cams can clunk as they seat when you pull away
Skip it if
Skip it on a short, light trailer - the cam system is aimed at trailers long enough to generate real yaw, and on a small utility trailer it is complexity for nothing.
#ad Affiliate link - we publish no price; Amazon shows the current one
Raw specifications: Reese’s own page. We earn nothing on that link.
4. For loading safely
Camco Trailer Wheel Chocks
Camco · Best for every trailer, without exception
Chocks go in before you unhitch, every time. They are not an upgrade and they are not interesting; they are the thing standing between a parked trailer and a slow roll down a campground slope.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Cheap insurance against the most preventable trailer accident there is
- Works on any trailer regardless of brakes or jack type
- Takes seconds and needs no setup
What does not
- Plastic chocks degrade in sun over several seasons
- Easy to leave behind at a site
Skip it if
There is no situation where you should skip chocks - if these do not suit your tire size, buy different ones rather than none.
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Once the load is right, a friction sway control bar is the cheapest effective addition - it damps yaw directly and does not interfere with the receiver's weight-carrying rating. If the tongue weight has turned out high enough that the tow vehicle squats, that is a load transfer problem rather than a sway problem, and a dual-cam weight distribution system both levels the rig and restores the trailer to straight. The three main sway mechanisms work differently and the choice follows from which symptom you have.
What will not help is adding sway hardware to a backwards-loaded car. The hardware is fighting a pendulum you created on the ramps, and it will lose.
Key takeaways
- Load a front-engined car nose-first toward the tow vehicle.
- The heaviest part of any load belongs ahead of the trailer's axles.
- Aim for 10 to 15 percent tongue weight, not the maximum you can make.
- Strap at the wheels so the car cannot creep rearward in transit.
- Fix the loading before buying hardware - hardware cannot beat a pendulum.
How we sourced this
Every figure on this page came from one of the following, each fetched while the page was written. Where a manufacturer or regulator does not publish a number, we say so rather than estimate it.
- CURT sway control kit - published specifications (part 17200)
- Sherline Products - manufacturer site
- 49 CFR 393.70 - coupling devices and towing methods, including safety chain and cable arrangement
- 49 CFR 567.4 - certification label content, including Gross Vehicle Weight Rating and Gross Axle Weight Rating
Common questions
- Which way should I load a car on a trailer?
- Nose first, facing the tow vehicle, for almost every front-engined vehicle. That puts the engine ahead of the trailer's axles and produces the tongue weight the trailer needs to be stable. A mid or rear-engined car usually goes on the other way round for the same reason.
- Why does my car trailer sway?
- Most often because the load sits too far back, which is what happens when a front-engined car is loaded backwards or parked behind the axle line. Too little tongue weight is the mechanism; loading direction is usually the cause.
- Do I need a weight distribution hitch for a car hauler?
- Only if the measured tongue weight exceeds your receiver's weight-carrying rating, or the tow vehicle squats when hitched. If the vehicle sits level and the trailer merely wanders, a friction sway control bar is the right and much cheaper answer.
- How much tongue weight should a loaded car trailer have?
- Between 10 and 15 percent of the combined weight of the trailer and the vehicle on it. Measure it loaded and strapped rather than calculating it, because where the car ends up on the deck changes the figure considerably.
More in Trailer Sway & Sway Control
Sway is almost never a mystery. It comes down to tongue weight, load position or speed - and only one of those three costs money to fix.
Read next
Troubleshooting
Trailer Fishtailing
What makes a mild wobble escalate into a full fishtail, how to end an episode without making it worse, and what to change afterwards.
Guide
How to Balance a Trailer
Loading a trailer so it tows straight: the 60/40 rule, where heavy items belong, and how to confirm the result with a measurement.
Head to head
Sway Control Types Compared
Damping versus a restoring force versus always-on friction - what each mechanism does and when each one lets you down.
How to
Measuring Tongue Weight
Three methods for measuring tongue weight, what each one requires, and how to interpret the result against the 10-15 percent band.
Guide
Preventing Trailer Sway
The pre-trip loading and setup routine that stops sway starting, plus the habits that quietly cause it.
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