suspension problems
Okay, so I will try to make this as short and to the point as I possibly can. I recently purchased a used 2013 Forest River XLR Thunderbolt fifth wheel toy hauler. I must say it is a massive upgrade...
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I was only using the 2" as an example. But I think you are headed in the right direction. I'd probably jack up the trailer to get the load off the springs and measure their unloaded length. Your loaded length is 1/2" too long so just buy springs that are about 1/2" shorter than what you have. Of course, if you re-order springs with a different load rating and/or arch, this will screw up your calculations.
Also, check to see if they are bound up under load. If your shackles are pushed to their max, they may actually be restricting the growth of the springs a bit. So you might need to subtract a little more than 1/2" to account for that.
The last thing to check (if you pull the springs off) is the location of the center locating pin for the axle. I've seen leaf springs where this pin is not exactly centered. When I did the lift kit on my Bronco, the leaf springs did have a front and rear with the locating pin offset to account for shackle movement. I don't know if trailer springs have this or not, but its worth checking.
Also, check to see if they are bound up under load. If your shackles are pushed to their max, they may actually be restricting the growth of the springs a bit. So you might need to subtract a little more than 1/2" to account for that.
The last thing to check (if you pull the springs off) is the location of the center locating pin for the axle. I've seen leaf springs where this pin is not exactly centered. When I did the lift kit on my Bronco, the leaf springs did have a front and rear with the locating pin offset to account for shackle movement. I don't know if trailer springs have this or not, but its worth checking.
