When did "D.O.T." Marking 1st appear on tires?
 

When did the dot letters 1st appear on tires?

1970 ish.

I think it maybe earlier... I have had some assembly line correct tires from as early as 1968 with DOT markings. For my survivor '67 390hp Corvette convert, we have a set of non-dot tires.

From what I remember 1968 started DOT numbers on all tires. Thats one of the reasons original 1967. Dated Corvette tires are worth so much. As an example, you could get Uniroyal Loredo 775X15 "The Rain" Tires up until 1971? But after 1967, they had DOT numbers on them. Thats what all the judges looked for. People try to sell "Original" spare tires and people try to make a set, but on closer inspection they are from later years. Another reason I took the point deduction and purchased reproduction tires

Bill

I believe it was January 1968 not the start of the model year 1968.