Originally Posted by Harry W
I installed Henschen axles on my '78 Sovreign and have recently noticed uneven side to side tire wear. The spacing between the axles at the wheel rim is 7/16" wider on the left side than it is on the right. The axles may have been aligned when manufactured, but apparently the holes in the trailer frame were not. There was no significant bolt hole clearance in the frame, so the axles are where they always were.
Oasis in Tucson said "That sometimes happens". So alignment is required , and soon!
There are two possibilities to install aligned axles on some earlier Airstream trailers, and yet have them misaligned.
The first would be the position of the axle mounting plate from one side to the other.
That can easily be checked by measuring from the center of the jack post to the most forward axle mounting bolt hole, or to the forward shock stud. That measurement should be exactly the same. A 1/8 inch axle mounting plate difference on a 31 foot Airstream, will make it tow dog leg about 2 1/2 to 3 inches.
The second cause of misalignment can be the location side to side of the frame with respect to the shell. The distance between the tires or frame from one side to the other should be exactly the same. If not, then realignment of a perfectly aligned axle is necessary.
What caused that problem was the manner in which the floor was attached to the frame. The chassis was in it's normal position on the concrete floor. The floor was put on top of the chassis and fastened in place, at the front and rear "ONLY." The chassis with the floor partially attached was then lifted so that the curb side (usually) was almost touching the concrete and the road side was high in the air. Then the remainder of the floor to frame hold down screws were added. When completed, the chassis was again placed, with the tires, back on the concrete.
What happened was the chassis because of it's weight, would sag in the middle when it was in the vertical position, and when the floor bolts were installed, it locked the chassis into a bend horizontally, from side to side.
That in turn caused the frame to be closer the exterior shell on one side than the other. Of course, that also meant that the tire or tires were also closer on one side than the other.
There is no easy fix for that problem, unless you do a shell off floor replacement.
Many people who do the shell off floor replacement are aware that the chassis must be level so that the shell will go back on properly.
But rarely, are those same people aware that the chassis can be out of alignment, side ways.
Therefore part of the reconstruction is to make absolutely certain the the chassis is level from front to back, and, also to make super sure that the frame is in an absolute straight line, front to back.
Failure to set the frame up correctly, will cause the shell to frame reattachment to be incorrect.