There were no regulations about the state of tyres in those days. I remember one farm on which I worked, and a truck came loaded with ground loimestone to spread on some of the fields (an ancient practice to sweeten the soil and improve the ph). This was a converted military truck, 6x4, unrecognisable with white dust stuck to it all over. It went a little way down the firm track, then tried to turn up-hill onto the land to be treated. The land was clay, wet and slippery. The dual rear wheels churne=ned round and round, and it wasn't going anytwhere. He made several attampts in different places. All the while the tyres were trailiing loose flaps of rubber - they were re -treads, already sheredded with working on the land and getting stuck. The tyres were like an old pair of rubber boots, totally shagged. Cue for session in the barn bringing things to a conclusion.