A suspension for vans or semi-trailers has a sliding (or slider) frame that can be slid longitudinally between spaced, left and right trailer stringers. The sliding frame is coupled within the stringers for longitudinal sliding between forward and rearward extremes. The sliding frame is formed by a pair of left and right rails spaced by two or three or more cross members. The sliding frame has an even number of independent air-spring support towers. The support towers are welded to the rails, but the cross members are bolted. The air-spring support towers can take semi-funnel shapes to having a lower narrower end forming an air-spring seat, and flaring upwardly from there to upper ends connected high on the rails to funnel the weight of the van or trailer from over a wider area to more of a pinpoint distribution on the air-spring seat.