Green’s Dictionary of Slang

treddlie n.

also treadly
[SE treadle, ‘A lever worked by the foot in machines and mechanical contrivances’ (OED)]

(Aus.) a child’s bicycle.

[Aus]Aus. Word Map 🌐 treadly. a bicycle. I rode my treddly to the shop. Compare deadly treadly.
[Aus]T. Winton ‘Family’ in Turning (2005) 175: He was the youngest of a feral mob of kids who roamed the town on their treddlies.