38 a front cross pivot 39 and intermediate cross members 41 a rear axle 42 is disposed beneath the rear frame 36 and paired wheels 43 are carried on the axle for free turning movement the axle and wheels hold the main frame 36 above the supporting ground a towing extension 44 extends forwardly from the main frame and its front cross pivot 39 such cross pivot 39 provides the interconnection between the towing extension 44 and the main frame 36 the pivotal joinder illustrated makes it possible for the towing extension 44 and the main frame 36 to be disposed at various alternate angles one with respect to the other when different motorcycles are to be accommodated and also when the trailer carrier 31 is to be stored the forwardly disposed towing extension 44 has side frames 47 that are narrowed at the front end to engage the pivot support bar 32 the support bar 32 is itself designed for engagement in the journals 6 8 provided by bolster plate 3 at an intermediate point along the front side frames 47 adjustment blocks 46 are provided these blocks have a plurality of openings 48 through which bolts 49 may be selectively disposed front fork support elements 51 are joined to the front side frames 47 and blocks 46 by the through bolts 49 if the bolts 49 are properly positioned the fork support elements 51 will be disposed in line with the front fork assembly 20 of the motorcycle 11 angle plates 52 at the free ends of the fork support elements 51 are provided with a plurality of holes 53 through which u bolts 56 or other fasteners may be extended the u bolts or other fasteners are provided for engagement with the.