Just bought new twin axle TT. When measuring between the tires on each side there is about 3/8 in difference.Some component of the axles,tire mounts or such must be slightly out of parallel. Salesman said no problem. Is that enough to be concerned about?

Yes it is a problem. While the tires may and will flex some, it still is putting extra stress and wear on the tires, bearings and every component of the suspension. Contact the manufacturer and get a spec, my guess is 1/8 inch or less although they may measure the difference in degrees.

Unless you have the trailer sitting on a 100% level surface, the trailer itself perfectly level and perfect as far as measurements from frame to level surface, along with some other things, you can not determine alignment in any accurate way. Even with all that done you're only doing half arsed guessing. There is enough play in the suspension, movement in the equalizer, differences in the tires etc to throw of your results to the point of them being worthless. The spread on the tires changes with equalizer movement on a conventional leaf spring setup, or with travel on a torsion arrangement.The only way to determine it is accurate measurements on the frame from the center point of coupler or A frame attachment points to the spring hangers or axle attachment points.

What Cramden said was correct for aligning the axle to the trailer frame for a single axle, and then it is a matter of ensuring that the second axle is parallel to the first. In your case the axles are not described as parallel, which can be checked for potential tire cause by measuring space between axles. I just did a quick google search, and the 1/8 inch measurement appears pretty close for the axle to frame requirement, but the paralleling of the axles should be near perfect.

Cramdon is correct ! Even loading will spread and move axles .

As previous suggested, your measurement may not be "good" depending on the conditions that it was done under since the suspension may not be totally at "rest" / "neutral" position. You may need to pull it to a long flat surface and travel in a straight line for a bit to allow the suspension to "set", then measure and see if it compares, then repeat and compare once more. If it is out after that, as suggested, you should potentially get it looked at for suspension check (loose components) and ultimately an alignment.... otherwise, you may be eating tires in quick fashion down the road.

? Equal spacing of tires important? | Good Sam Community

kerrlakeRoo
Explorer
Aug 18, 2018
Yes it is a problem. While the tires may and will flex some, it still is putting extra stress and wear on the tires, bearings and every component of the suspension.
Contact the manufacturer and get a spec, my guess is 1/8 inch or less although they may measure the difference in degrees.
Ralph_Cramden
Explorer II
Aug 18, 2018
Unless you have the trailer sitting on a 100% level surface, the trailer itself perfectly level and perfect as far as measurements from frame to level surface, along with some other things, you can not determine alignment in any accurate way. Even with all that done you're only doing half arsed guessing. There is enough play in the suspension, movement in the equalizer, differences in the tires etc to throw of your results to the point of them being worthless. The spread on the tires changes with equalizer movement on a conventional leaf spring setup, or with travel on a torsion arrangement.

The only way to determine it is accurate measurements on the frame from the center point of coupler or A frame attachment points to the spring hangers or axle attachment points.
kerrlakeRoo
Explorer
Aug 18, 2018
What Cramden said was correct for aligning the axle to the trailer frame for a single axle, and then it is a matter of ensuring that the second axle is parallel to the first.
In your case the axles are not described as parallel, which can be checked for potential tire cause by measuring space between axles.

I just did a quick google search, and the 1/8 inch measurement appears pretty close for the axle to frame requirement, but the paralleling of the axles should be near perfect.
wanderingbob
Explorer II
Aug 18, 2018
Cramdon is correct ! Even loading will spread and move axles .
budwich
Explorer
Aug 18, 2018
As previous suggested, your measurement may not be "good" depending on the conditions that it was done under since the suspension may not be totally at "rest" / "neutral" position. You may need to pull it to a long flat surface and travel in a straight line for a bit to allow the suspension to "set", then measure and see if it compares, then repeat and compare once more. If it is out after that, as suggested, you should potentially get it looked at for suspension check (loose components) and ultimately an alignment.... otherwise, you may be eating tires in quick fashion down the road.
goducks10
Explorer
Aug 18, 2018
Ralph Cramden wrote:
Unless you have the trailer sitting on a 100% level surface, the trailer itself perfectly level and perfect as far as measurements from frame to level surface, along with some other things, you can not determine alignment in any accurate way. Even with all that done you're only doing half arsed guessing. There is enough play in the suspension, movement in the equalizer, differences in the tires etc to throw of your results to the point of them being worthless. The spread on the tires changes with equalizer movement on a conventional leaf spring setup, or with travel on a torsion arrangement.

The only way to determine it is accurate measurements on the frame from the center point of coupler or A frame attachment points to the spring hangers or axle attachment points.

x2
RCMAN46
Explorer
Aug 18, 2018
Easy way to check suspension attachment points.

Have the trailer on a flat and as near level surface preferably smooth concrete. Make sure trailer is level.

With a plumb bob attach to the bolts that go through each spring hanger and the equalizer hanger. I loop the plumb bob string on the front side of each hanger through bolt.

Then I lower the plumb bob until it just touches the floor. With a magic marker I mark these points on the floor. I do the same for the coupler at the front center of the coupler.

Then move trailer away and make measurements.

I would not expect to find any comparable measurement more than 1/8 inch in error.

If the hangers are OK then suggest checking for a broken spring or a sheared spring center bolt.

I had a friend who found his trailer hangers on one side of the trailer were one inch behind the the other side.
ken56
Explorer
Aug 18, 2018
Keep an eye on your tire wear. If its a major alignment problem it won't take long for it to reveal itself. I would hope that today RV frames are made in a jig so to prevent the misplacement of the hangers....but what do I know. That would be to easy for them to implement if they aren't doing it now.
Huntindog
Explorer
Aug 18, 2018
Dr. Feelgood wrote:
Just bought new twin axle TT. When measuring between the tires on each side there is about 3/8 in difference.Some component of the axles,tire mounts or such must be slightly out of parallel. Salesman said no problem. Is that enough to be concerned about?
Measuring the way you did it is worthless.
The distance between the tires is constantly changing as the equalizer moves. It is next to impossible to get an accurate measurement because of this.

Measure the spring hanger locations. There are several methods, some mentioned here already.

The hangers will not move,(unless broken) so that measurement can be relied upon.
Ralph_Cramden
Explorer II
Aug 19, 2018
ken56 wrote:
Keep an eye on your tire wear. If its a major alignment problem it won't take long for it to reveal itself. I would hope that today RV frames are made in a jig so to prevent the misplacement of the hangers....but what do I know. That would be to easy for them to implement if they aren't doing it now.

Most of todays trailer frames are made in a jig, but with workers making $12.50 an hour, using low grade materials, along with sub par engineering at Lippert.

As far as dropping plumb bobs to floors that may get you a measurment thats close to accurate, but it may not. Very few rigs load the suspension equally due to non balanced weight, such as slideouts or the weight of cabinets all being on one side. But then again A trailer does not have to be aligned as close as a Nascar stock car built on a leveling plate.