How To Stop Utility Trailer Bounce
If you pull an empty (or nearly empty) utility trailer, you probably know the feeling of utility trailer bounce. It’s that bumpy jolting extra bouncing you feelin the tow vehicle as you drive. Sometimes it feels like the trailer is just bouncing away behind you, yet it’s not, but really it is.
What Causes Trailer Bounce?
The simple answer is the suspension is too stiff for the load. There are other parts to it, like load balance and the axle position, but we’ll get to those in a minute. Basically utility trailer bounce happens when there is not enough compliance in the system for the current load.
If your trailer is rated at 3500#, and you’re pulling it empty (maybe 500# trailer weight), then the suspension is not going to compress much over a bump. Instead, it bounces — and sometimes keeps bouncing because full tires are like basketballs on the ends of the axle.
Remember, a trailer suspension is a system that includes both the springs (or rubber) and the tires.
To make matters worse, depending on trailer length and where the axle is placed, when the car goes up and down over a bump, that teeters the trailer like a teeter-totter. The mass of the trailer frame wants to keep moving even as the shock absorbers on the car are trying to smooth things out. Then, the trailer tires go over the bump and the mass of the frame is excited again. All of this jostling makes pulling the trailer somewhat annoying, if not disconcerting.
Pulling a trailer in a truck with a stiff suspension also amplifies the effect. And, if the trailer is quite heavy and/or long, that makes things worse too. Finally, the smaller the tow vehicle (compared to the trailer), the greater the effect.
So, is there a way to fix it? Can we make it go away?
Utility Trailer Bounce Solutions
The focus here is on utility trailers because they are often pulled empty, then full, then empty. They also have a large difference in load from empty to full, so it’s often called “utility trailer bounce”. It happens with other trailers too, and what you are feeling is not only bounce, but all the movements of the trailer.
Can we fix it? The honest answer is NO. BUT, you CAN calm it down considerably!
The easiest way to reduce utility trailer bounce is to adjust tire pressure. By lowering pressure, the tires act more like a partially filled basketball and they bounce less. How much pressure? That depends on trailer weight, tire size, and tire type (trailer tires or automotive tires). In general, for an empty trailer, you can run half the normal pressure.
For one trailer I had with 225-70 R15 automotive tires, normal pressure was 35psi. Trailer empty weight was 400 lbs. When empty I ran 12-15 psi which smoothed things out superbly. Automotive tires usually require a little more pressure because they have softer side walls. Radials especially.
Please don’t take my word on it, experiment with your trailer. Try reducing by 10psi, then go down in 5 psi increments until the bounce is acceptable. It won’t go away completely.
With very low pressures you run several risks of tire damage, so don’t go too low. It won’t wear the tire more quickly when the trailer is empty, so that’s not a problem, but a big bump can cause other trouble. Also, if you’re taking the trailer to pick up a big load, make sure you also carry an auxiliary tank or pump — because you DON’T want to haul a load with low tire pressure.
There are some rubber inserts on some shackles that dampen some of the bouncing. They can be expensive, and limited in the effect they have.
If it’s practical, add a longer tongue or set the axles back some. These also reduce the bouncing you feel in the tow vehicle.
Torsion axles are a little better for bouncing than leaf springs, because rubber has a natural hysteresis. However, running empty you don’t deflect the torsion much (if any), so there is not much of an effect.
Also, tandem axles reduce bouncing some because they interact with each other to mitigate some of it.