Axle-Load Tandem Slide
Over/under per axle group, weight shift per slider hole (lever-arm), holes to slide and direction, and projected drive/trailer weights to bring a tandem under the legal cap.
Formula and source
Lever-arm: moving the tandem d inches changes the trailer reaction by dW = trailer_load * d / L (L = kingpin-to-tandem). shift_per_hole = trailer * hole_spacing / L; holes = ceil(target_shift / shift_per_hole).
Per the federal axle/gross weight limits - 23 CFR 658.17 (12,000 lb steer, 34,000 lb tandem, 80,000 lb gross) and the federal Bridge Formula, by name; lever-arm statics is public.
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