Bullseye240
Adventurer
Good diagram.
With the weight of the trailer and an approximate 50% loaded weight on the axle with jack-stands and the wheels off. The reason for 50% loaded weight is so that when fully loaded or unloaded it moves within allowable specs.
Take a straight edge or tube/pipe/square tubing and clamp them to the hubs by bolting on with the lug nuts or clamping onto the mounting surface and level them as indicated by the green line in the above. You can also rotate the fixture vertical to measure camber with this setup.
Run two strings between the left and right side (Dimension A in the above) and measure for toe in or out. Set toe to zero or slightly toed in.
After finding the center of the strings mark it on the string.
Attach another string to the rear cross string and run it over the front cross string to the hitch. Tie it to a jack-stand and while keeping it taught slide the jack-stand left or right until it lines up with the centerline on the front cross string.
Drop a plumb bob from the centerline of the hitch or tongue. If the strings do not line up with the hitch the trailer will not pull straight. Not a huge deal on a trailer this length but probably fixable with the given adjustments.
Keep in mind that if the string runs parallel to the tongue but not on the centerline of the tongue it indicates that your axle is square to the centerline but not centered to the tongue.
This would cause a situation like image "B' in the one I posted where the measurement from hitch to axle end would falsely indicate square but the axle or tongue is shifted off centerline and would cause tracking issues. You need to either move the axle left/right or move the tongue left/right to center it. Again on a trailer this length it would be less critical but would eliminate confusion when trying to diagnose irregular tire wear and tracking issues.
Getting the axle/s centered along the line of pull ensure the trailer will track well and wear tires evenly. I would shoot for about a 1/16" to 1/8" inch toe in to provide a slight scrubbing of the tires to eliminate erosion wear of the tire tread if using highway tread trailer tires and allow for bearing wear between service intervals as the bearings will loosen a bit as they wear and then begin to toe outwards but still be within specs.
