Abstract: Running gear comprises a beam having upwardly directed, aligned, first brackets at or towards each end for attachment of the beam transversely to a trailer, aligned second brackets depending from the beam at or towards its ends, at least one third bracket depending from the beam in alignment with and intermediate the second brackets, arms respectively pivoted at their front ends to a second bracket and the or a third bracket and carrying stub axles at their rear ends on which are brake means and wheel mounting means, and rigid with and extending rearwardly from each arm and stub axle assembly a member having a platform for an air spring. The running gear is fixed as a unit to a trailer chassis by the first brackets. Preferably the beam is tubular of vertically elongated hexagonal cross-section, and upper and lower regions of the section are embraced by the first and second brackets respectively.