Springs over or under axle?

[ISh]

I am building a trailer to haul 11,500lbs (excavator). I have slipper springs. The axles are 7000lb axles. The spring pads need to be welded to the axle so I can put the springs over or under the axle. I would like to keep the trailer low so I would like to put them under the axle. I also have enough clearance to put the spring under. Will the ubolts keep stretching or fatigue oever time??

 

[Ragain]

Dexter axle or Kelsey-Hayes has specs on recommended applications. I don't believe that I have ever seen an axle placement under the spring pack though. Trick is to keep load center as low as possible. Are you planning on a three axle set for your excavator? Something to consider is the loaded trailer more than likely will be pulled over uneven terrain, and with 11,500# combined with your empty trailer, (7,500-8,500# ?) you could potentially overload any one axle while going over a small dirt mound. Personally... . I would be more confident with a pair of 12k axles running duals on each.

 

[ISh]

I have two 7000lb axles. The cost difference between two 12klb axles and eight tires and wheels vs. two 7klb axles with four tires and wheels is significant. I won't going be going long distances or very fast.