axle alignment at home

[dznf0g]

This came up in another thread awhile ago. "Do I have to get an axle alignment after installing a lift kit" was the question.

After installing new axles or a lift kit at home, there is a very easy and precise way to ensure alignment to the frame.

First, purchase a laser measure. They are inexpensive, have many uses and are a lot cheaper than taking the trailer to an alignment shop...if you can find one.
This is the unit I got:

https://www.amazon.com/dp/B0863RK1KX...t_details&th=1

Ensure that whatever unit you choose, it has a "sweeping" function. This allows you to shoot the jack post and readily find the closest point on a round shaft so that measuring both ends of the axle will be accurate.

Next, level the trailer. Get a jack stand and set its height to be as close to the a-frame as possible. Raise the tongue jack and re-lower it so it is not cocked in its housing. (frequently, when unhitching and leveling the trailer afterward, the jack leg will be cocked in its bore) Re-level the trailer.

Make yourself a plate setup like pictured here:





I utilized a steel plate and a strong rare earth magnet along with a couple magnets in the vertical axle flange plate (not pictured). Note the need for a "wedge" to angle the laser measure downward to clear spare tire, etc. I used a simple shim for construction purposes.

Point the laser at the tongue jack and activate the sweep function. Slowly move the laser measure side-to-side on the jack post. The shortest measurement captured is the accurate dimension you are looking for.

Once you have both front axle-to-jack figures, verify they are equal. If not, you will need to re-position the axle.

Once the front axle is aligned, Simply place the rear base of the laser measure against the rear face of the front axle tube and shoot the front surface of the rear axle. Repeat for the other side. The dimensions should be equal.



Using this methodology, after my recent axle replacement I was able to verify both my axles are square to the jack and thus the coupler.

Keep in mind this process is only to ensure the axles are square to the chassis. It does not check for a bent axle or spindles. There is another process for that.

[dznf0g]

These were my measured dimensions. Either the shop performed similar activity while installing my axles, or the manufacture of the frame and axle plates are pretty precise.

[crispyboy]

The laser measuring device is interesting. When I replaced the trailer axles I hung a plumb bob down from the front of the hitch. I felt more confident in this than using the jack post. Worried the frame holding the jack post could have been tweaked by the previous owner.

[dznf0g]

Originally Posted by crispyboy

The laser measuring device is interesting. When I replaced the trailer axles I hung a plumb bob down from the front of the hitch. I felt more confident in this than using the jack post. Worried the frame holding the jack post could have been tweaked by the previous owner.

Yup, if you don't get equal measurements, you really have 3 points to diagnose and verify. The laser measure has a Pythagoran function which would help with that if you have a suspect jack post.
I think if you wanted to use the coupler, you would have to make a pretty elaborate "plum bob". I don't think the laser can see a string or rope.

[Belegedhel]

I have a similar device, and just feel like I need to point out that the device mentioned very probably does not make its measurement based on laser technology, rather, it uses a laser to point at what you are measuring, and then bounces an acoustic wave to take the actual measurement. The acoustic wave is not going to have the pin-point accuracy of a laser beam. You might have more precision using a simple tape measure.

[dznf0g]

I don't believe this unit is acoustic in any way. It is a class 2 laser. That said, this lower cost one has a 2mm resolution. That is certainly accurate enough for alignment of a trailer, and more accurate than I can accomplish with a tape.



"Class 2 lasers are low power (< 1mW), visible light lasers that could possibly cause damage to a person's eyes. Some examples of Class 2 laser use are: classroom demonstrations, laser pointers, aiming devices and range finding equipment."

Also, look at the front of the unit in the pics in post 1. There are 2 optical lenses. The large one is a light collecting lense. Everything in the operating instructions refer to the reflection surface of the target and bright lighting conditions (backlighting) preventing the ability to take a reading.

[dznf0g]

Also, since you questioned accuracy, I scaled it against a tape measure. I got one that was calibrated well, apparently.



According to the documentation, the plus or minus of 2mm will be consistent throughout its certified range (50m for this model).

[richard5933]

Originally Posted by crispyboy

The laser measuring device is interesting. When I replaced the trailer axles I hung a plumb bob down from the front of the hitch. I felt more confident in this than using the jack post. Worried the frame holding the jack post could have been tweaked by the previous owner.

I did the same thing - a plumb bob hanging from the very front-center of the hitch and then made a mark on the ground beneath it. I didn't trust that the jack's post was held in a perfectly straight orientation once the weight of the trailer was on it.

With the wheels and tires removed, I then used a large pair of construction squares to mark a point directly under the center of end of each axle.

Once I had the four axle ends and the trailer from marked, it was simple to use a good tape measure to check the alignment, which in the end I was able to get tuned in with less than a 1/16" variance all around.

[dznf0g]

I never really trusted that the a-frame was exactly 25* on each side and/or that the coupler is welded on straight. The old Hensley and the (pp) always run a bit off center, regardless of the road crown direction. Both have adjustments for that, but I found it strange that both hitches behaved the same way on multiple tow vehicles. I use a little wireless camera for that adjustment.

[Life is a Highway]

I commend your sprit. Me I leave it to the axle techs. Trying to measure degrees with a yardstick approach would drive my OCD nuts.

You working tech’s trained on a Hunter alignment system understand.

[rogerdpack]

Nice, a youtube on it would be nice as well
By sweeping I guess you mean it can measure as you rotate the laser? I didn't see any mention of sweeping on that amazon one but I guess it can? Cheers

[dznf0g]

Originally Posted by rogerdpack

Nice, a youtube on it would be nice as well
By sweeping I guess you mean it can measure as you rotate the laser? I didn't see any mention of sweeping on that amazon one but I guess it can? Cheers

They call it continuous measurement, which I didn't think was very descriptive.

[rogerdpack]

Nice, I might try something similar to double check rear axles on my brother's bounder next time I try to align the front And it sparked a fun triangulation idea for aligning my car.

[dznf0g]

Originally Posted by rogerdpack

Nice, I might try something similar to double check rear axles on my brother's bounder next time I try to align the front And it sparked a fun triangulation idea for aligning my car.

Trailer toe (and car) can be checked too, IF you have decent line of sight access. Probably don't though.