As an RV inspector and mobile technician, one common issue I see when working with travel trailers and 5th wheels is tire wear. When I see unusual tire wear, the first thing I ask the seller or owner is when was the last time they had the alignment checked. Unfortunately, I most often get a glazed look with the answer of never. Just like our automobiles, a trailer takes the same kind of abuse going down our pothole-riddled streets and highways, and they need alignments too. Trailer alignment can easily be checked for preventative measures, but an accurate alignment should be done once every year or two depending on the amount of traveling that you do.
If you start to notice uneven tire wear on one or more wheels, your trailer is telling you that it needs immediate attention, and you can take some simple measurements to determine where the issue might be. These checks and measures are not meant to replace a proper trailer alignment.
First, you will want to set the trailer on a level surface. When maneuvering the trailer into its place, you will want to pull forward for about 100 feet to its spot to straighten any of the torsion on the wheels that is caused by backing a dual wheel trailer into place. Once you have the trailer set, chocked, and leveled, you will need to grab a straight edge that is longer than the width of the two wheels on each side of the RV. I have an 8’ level for this purpose, but any straight bar will work. Grab a helper to hold the bar in place while you measure.
Following the diagrams below, place the straight edge across each wheel along its centerline and measure the distance between the straight edge and frame at each point 1 through 4 and record the measurements.
Next, using the image to the left, you will want to take a measurement from the hitch point (A) to the centerline of each of the front tires (D and E) and record those measurements. Lastly, measure from the hitch point to each end of the frame (B and C) and record those measurements.
Now that you have all of those measurements, here is how to understand what you have.
If measurements 1, 2, 3, and 4 are all within 1/8” of each other, then your axles are aligned. If only one of those is out by more than 1/8” then that spindle is bent. If two on the same axle are more than 1/8” from the measurement of the other axle then one of your axles is bent. To determine the bent one, measure one tire at a time between points a. and b. (Image Right) and the good axle will measure within 1/8” on both sides at those points.
If measurements A to D and A to E (Image Left) are more than 1/8”from each other, then your front axle is shifted, and the trailer needs to be aligned.
If measurements A to B and A to C are more than 1/8” from each other, then the frame is shifted, and you should take the trailer to an alignment or frame shop for further diagnosis and repair.
Hopefully, now you will know what is causing that uneven tire wear and can take it to a shop to have some preventative maintenance done to save you from wearing your tires out prematurely or from having an unnecessary blow out going down the road.