A tag axle assembly and means for mounting it to a transit concrete mixing truck are disclosed. The assembly includes a tag axle frame having a forward, longitudinally extended stem and two rearwardly extending and diverging legs. The stem is mounted to a support frame by a pivot axle to pivot about a horizontal transverse axis. The support frame in turn is attached to the truck chassis. A flexible sleeve, connected between the pivot axle and stem, allows limited stem rotation about a longitudinal axis and a vertical transverse axis, permitting wheels supported by the legs to readily adjust to uneven terrain and to follow the steering and drive wheels of the truck without transverse skidding. The tag axle assembly is pivoted between operating and raised positions by a pair of pneumatic load springs extensible to pivot the assembly downward to the operating position, and a pair of pneumatic lift springs extensible to pivot the assembly upward to the raised position. Also disclosed is a similarly mounted tandem push axle assembly.