Taming the Trailer Tango; The Story of Trailer Whip
Hitting the road with a trailer in tow can be the perfect recipe for adventure. But that adventure can turn sour if you encounter the dreaded “trailer sway” – a scary situation where your trailer starts oscillating wildly behind your vehicle. Let’s explore what causes this instability and how to keep your trailer tracking straight.
Mass & Energy
Given today’s trend of ever smaller tow vehicles, more whip events is no surprise. The best single whip preventative measure is tire pressure. A whip cause that is neck & neck with light tow vehicles. That said, if the trailer is within ~60% of the tow vehicle weight, a sway preventive, load distribution hitch is required. Most of them serve both functions these days, but there are exceptions. A small percentage only distribute weight.
When we’re asked for professional advice on tow vehicles we only say that, ideally, for it to be twice the weight of any bumper pull trailer. This can’t always be achieved, so the other precautions suggested here should be applied.
Skill Vs. Engineered Safeguards
When I was still ten feet tall and bulletproof I regularly broke the weight ratio rule. I had a big truck and was, well, invincible. Ive shrunk and gotten softer these days and have studied whip dynamics well enough to understand the limits. Second to safety, engineered safeguards give peace of mind. If you are one who really knows how to get out of a whip (discussed later) you can pretty easily go with 1.5x the trailer weight. From there it is your call as to your skill and willingness to tolerate worry and necessary vigilance.
The Importance of Tire Pressure
Tire pressure is not only crucial to avoid costly blown tires, and even costlier repairs to your RV. It also causes or exacerbates tire roll. It is said that this is a small contributor to whip, but IT IS the cause of resonance and its severity.
Tire Roll is the phenomenon of your tires rotating longitudinally on their rigid wheels. Once your tire roll is initiated, elastic kinetic energy builds and releases. Viewed from the rear, when you are in the right side sway moment, your tires rotate clockwise. Now, if improper correction steering is applied, your trailer initiates a sway to the other side, your tires rotate counter-clockwise and the self sustaining resonance phenomenon which additionally provides and increases its own energy. Therein lies the resonance.
Under-inflated tires on both the tow vehicle and trailer can be dangerous. Many videos exist on YouTube of this process. Soft tires flex more, reducing handling and stability. Make sure all tires are inflated to the recommended pressure before you hit the road. About 5% over inflation is allowable when the tires are hot.
Or, better still, have stiffer tires installed. Off-road type tires are more rigid and thus reduce tire roll events and correct sway better. AND, they’re cool.
Either way, inflation pressure is king.
How Whip is Canceled
Once whip starts there will be brief moments in the cycle when the tow vehicle and trailer are aligned. I.e. when the trailer is right and the vehicle is left, but they are aligned at a degree or two right/left of the road azimuth. This lasts for a split second before the cycle restarts, and is the time corrections must be made. We’ve all heard of “Turn into the sway.” Right? Basically that means doing the opposite of the intuitive thing. Since The trailer is trying to send you out of your lane, it’s natural to want to turn out of it. But if you capitalize on the moment of alignment by holding your wheel straight in the skewed angle, the whip will soon cancel.
Bleeding off velocity, decelerating, will also cancel it. Both should be employed immediately and as confidently as possible.
Conclusion
The conclusion is up to you. Our final recommendation is: Weight matching and engineered safeguards (including tire pressure) are just worth it, and are best when coupled with skill.
