central supporting rod 5 therefore this built in construction may increase the operating security and may improve the durability of components the joining piece 552 of proper width slides stably within the sliding slot 51 of the lower central supporting rod 5 during the extension or collapse of the collapsible frame thereby avoiding the unstable and loose operation of the conventional golf carts referring to fig9 to 12 the fastening mechanism for joining the wheels 61 and 62 with the wheel supporting rods mainly comprises a metal plate assembly 63 wheels 61 and 62 a moveable element 64 a spring 65 and a pin 66 the metal plate assembly 63 is u shaped and has a pair of vertical plates each vertical plate is formed with an inclined extension having an axial hole 631 and a pivotal hole 632 the upper edge of the inner inclined extension has a shallow recess 633 the axle 621 of the wheel 62 is formed with a pair of slots 6211 and 6212 and said axle 621 is arranged to pass through an axle sleeve 622 of the wheel 62 the moveable element 64 is provided at one end with a flap 645 the lower portion of the flap 645 has a recess 644 the middle of the moveable element 64 has a.