showcrop
Well-known Member
Here's the deal. It is simply tire balance. It is most likely to occur with tandem duals, and it is exactly the same as with any tandem dual truck. No tire is perfectly balanced. They can be balanced closely but they are always going to be a little out. Normally the out of balance on the four axle ends will mostly cancel each other out, sometimes more sometimes less. As the vehicle, whether it is a truck or trailer, goes down the road, going around curves and around corners the tires on the outside are going to turn more, so the relationship of the out of balance to the other pairs of tires is going to constantly change. This is of course more pronounced with a truck than a trailer due to the slippage of driving vs. being towed. When in the course of the putting on miles, the out of balance of the axles gets together a very strong bounce when unloaded can develop. All drivers of a tandem truck will notice this. It comes and goes as you drive and it will occasionally get very strong but after awhile it goes away. My experience when driving a tri-axle dump is that it would happen only for maybe 6-8 miles and only every two-three days. It would be barely noticeable with one truck but very strong with another. The periods of bounce will last longer with a trailer because they change with respect to each other much more slowly than tires that are driving. The solution is simply to get the pairs of tires dynamically balanced on the axles. Alternatively a dynamic balance product such as IMI EQUAL FLEXX can be added inside the tire. When I had five trucks running my tire dealer installed it with all new tires and I found that it worked very well.
