Checking axle alignment

BoonHauler wrote:

RCMAN46 wrote:

rhagfo wrote:

dbbls wrote:
As long as both axles are parallel it doesn't matter about the distance to the king pin. If it is off a little all it will do is make the trailer follow a little to one side. Not enough to matter. It is not uncommon to see big rigs tracking sideways.

Not true! If the trailer is going down the road cocked to one side you will have tire scrub and if enough could be clearance issues in narrow spaces.

Not only that but the trailer will go to one side then snap back to center.

This can result in a little sway.

Most of us have seen some small trucks and vans that do this.

dbbls is kind of right and kind of wrong.

The lead axle MUST be set exactly perpendicular to the long axis of the trailer.

If the axle is perpendicular to the frame the distance from each spring hanger to the king pin will be the same. That is what that measurement checks. So he is dead wrong.

Once the lead axle has been set the trailing axle/s centerlines must be held equal on both sides.



Uneven side to side loading on the axles can also cause the Dog-Tracking

Here's a few links Trailer Design Considerations
and Trailer Resource Library

I set my axles to a 1/16th of an inch tolerance.

The spring hangers have to be welded in the correct location on the frame first and foremost. If they are not then the trailer probably will not tow well and will probably result in excessive tire wear.


Lippert has benn known to mess this up as a friend of mine found out.

BurbMan wrote:
Basically that's it. I see your 5er is new, but for older units, be sure to check the shackle bushings and suspension first.

This is a great post by member JBarca on replacing his axle and fabricating adjustable mounts so he could align the axles.

I used this Correct Track II bolt on alignment system, but the one that JBarca made as described in his post is more exact.



Essentially when you measure from the kingpin to both sides of the front axle, the measurements should be within 1/4", and same tolerance when measuring between the axle centers on both sides.

Had a look at JBarca's post. I hate guys like that. He has all of the toys & the place to use them.

Through the very basic measuring system of sticking a fist between the tires & feeling the difference each side I know that my alignment is out.

That Correct Track system is self doable during my spring boatyard visit. Checked the Lippert site & I am confused somewhat on what the kit supplies.

Does it contain the hardware for all 6 spring mount points? I already have the equaflex center mounts, which I like. Can they go back on?

N-Trouble wrote:
I was wanting to check the alignment of the axles on my trailer and was thinking of tying a weight to a string and hanging it from the kingpin then marking that spot on the ground. From there measure back to some point of the axle/wheel on each side and comparing. I realize this is a crude method compared to using a laser setup that I suspect most alignment shops probably use but would it at least tell me if I have any kind of alignment issue?

What you are looking at doing is checking the axle placement from the factory not the actual axle tow in or camber. The axles only have 4 none moving mounting points, the front spring mounts and the rear mounts for the back axle. So check the distance from the king pin to each front mount one each side and see if they are the same, all the rest of the mounts (equalizer and rear spring mounts) should be the same on both sides. If everything else is installed correctly and are the same parts the trailer will track correctly but the tow in and camber can still be off. The only way to set that is bending the axles on a alignment machine.

Denny

I have one 14k GN flatdeck trailer with 7k axles. The axles are 5/8" out of parallel axles however when measure at the end of the axle stubs everything is within tol. This trailer has some 48k miles/8 years on the tires with no wear issues of the tire or suspension.

I also have a 10k GVWR car hauler that had one tire wear issues. The alignment shop found the axles were parallel but one axle stub was probably not welded inline with the axle tube at the time of mfg. The shop bent the end of the tube so the axle stub would track the front axle.

I'm more concerned with the axle stub location/angle as it controls the direction of that wheels travel.

RCMAN46 wrote:

rhagfo wrote:

dbbls wrote:
As long as both axles are parallel it doesn't matter about the distance to the king pin. If it is off a little all it will do is make the trailer follow a little to one side. Not enough to matter. It is not uncommon to see big rigs tracking sideways.

Not true! If the trailer is going down the road cocked to one side you will have tire scrub and if enough could be clearance issues in narrow spaces.

Not only that but the trailer will go to one side then snap back to center.

This can result in a little sway.

Most of us have seen some small trucks and vans that do this.

dbbls is kind of right and kind of wrong.

The lead axle MUST be set exactly perpendicular to the long axis of the trailer.

Once the lead axle has been set the trailing axle/s centerlines must be held equal on both sides.

Uneven side to side loading on the axles can also cause the Dog-Tracking

Here's a few links Trailer Design Considerations
and Trailer Resource Library

I set my axles to a 1/16th of an inch tolerance.

rhagfo wrote:

dbbls wrote:
As long as both axles are parallel it doesn't matter about the distance to the king pin. If it is off a little all it will do is make the trailer follow a little to one side. Not enough to matter. It is not uncommon to see big rigs tracking sideways.

Not true! If the trailer is going down the road cocked to one side you will have tire scrub and if enough could be clearance issues in narrow spaces.

Not only that but the trailer will go to one side then snap back to center.

This can result in a little sway.

Most of us have seen some small trucks and vans that do this.

dbbls wrote:
As long as both axles are parallel it doesn't matter about the distance to the king pin. If it is off a little all it will do is make the trailer follow a little to one side. Not enough to matter. It is not uncommon to see big rigs tracking sideways.

Not true! If the trailer is going down the road cocked to one side you will have tire scrub and if enough could be clearance issues in narrow spaces.

It is a good idea to back up and pull forward several times to equalize everything before measuring. I added Correct Track to gain 2" of height. Used the plumb bob method to confirm that the axles were square to frame and king pin.

It might be common to see a commercial trailer dog tracking but that does not mean it's right. The king pin method may be crude as per say but it does work. 1/4" from the king pin to each side front axle difference is too much. 1/16" difference between axle centers on each side is too much. Both conditions will cause scalloping of the tires. You can make a trailer with a bent frame track straight behind the truck if you know what your doing, again it does not make it right.

Yes check that front tires are equal length to the hitch point. Should be within 1/4". Then check axles are parallel within 1/4". If you have tire wear issues remove the worst to inspect it while off the trailer.