Effects of trailer brakes and sway

Turtle n Peeps wrote:
I think Mikes point is there is no (built in) toe in a trailer axel. I agree with him.

Is there a spec? Sure! There is spec's for everything. Otherwise people like me would put a set of gauges on a brand new axel and reject it because it has .07 degrees of toe in it. This way the manufactures can say, "that's within our spec's so it's fine."

Hi Turtle n Peeps,

I am "thinking" by your response there is miss-understanding on the word "built in". I can tell you agree as I do, that toe on a trailer axle since it does not steer is in the 0 degree range. And yes there is a specification for toe of the axle which comes in the form of a tolerance based around the 0 target. I think we agree on this? Yes/no? Think about this process I'm describing below.

Now to how do they "build" an axle. The axle spindle shafts or stub ends, (the machined ends where the wheel bearings are with the brake drum or hub) are machined at a separate operation from the main axle tube. The axle tube is made from a certain grade of steel, size and wall thickness pending the load rating of the axle. There is a welding process that joins the axle spindles to the end of the axle tube. This is a critical controlled process so the heat shrinking of the weld does not distort the position of the axle spindle ends. If the welding warps the spindle joint wrong, the toe settings can be very far off of where they are supposed to be.

Trailer axles also have camber built into them. Pending the load rating they bend the axle in the center up in relation to the top of the axle to a specification with a tolerance to create a positive camber setting at the wheel location for the load rating of the axle.

There is also the axle seat installation as well as well as a brake plate mounting ring if it they are making a brake axle. They install (fabricate, build etc.) the axle seat from a formed sub-assembly and pending the weight rating, they may add reinforcement plates on the ends of the axle seat in that sub-assembly. These axle seats are then welded onto the axle tube in relation to the center of the axle left to right, and for "radial" positioning. The brake mounting plate ring also follows this radial positioning. They find the "top" of the axle tube which we will call 0 for this discussion. The bent camber setting is up and on top at this 0 mark. They clock or rotate the spring attaching side of the axle seat so the camber and toe setting built into the axle are within an acceptable tolerance when the axle seat side is mounted to the leaf spring which is at this 0 or 12:00 position. The axle seat spring mounting face is true horizontal when at the 0 position as viewed from the spindle end. If they welded the axle seat many degrees off radial position, say 5 or 10 degrees out of location of the zero mark, then the axle toe setting can be affected at the wheel as the camber bend in the axle tube would rotate the axle spindle end to no longer be in the correct plane. If the axle was true straight with no positive camber, then it would not matter, but we have positive camber and need to deal with it.

After all this welding and bending is done they have a QC check to insure the axle assembly is built within their specifications for all the important dimensions. Toe and camber are created at the wheel by being built into the axle assembly. Toe and camber are considered non adjustable short of some repair shops bending the axle tubes trying to get them back into specification.

There are other steps in the making axle assemblies I'm sure I did not list, but what I did list are some of the larger points I was trying to make. My point was they are "building" the axle with a toe setting "built into" the assembly on purpose. In this case the setting is 0 degrees with a tolerance range at the wheel.

I'm assuming you may agree with the process I described above in general terms as I can tell by your responses you agree we have a 0 degree target. If they did not build in a 0 setting for toe then the toe at the wheel could end up being excessively in the wrong place and never work correctly.

That is the context of the wording "built in" I was using. What were you referring to when toe is "not built in"?

Hope this helps explain this better.

John