What a retread plant does
Retreading puts new tread onto a casing that still has structure in it. The casing is the expensive part of a tire to manufacture, and a well-treated one outlives several treads. Scrapping a tire when the tread wears out throws away the half that cost the most.
The sequence is inspection, buffing off the old tread, repairing what is repairable, applying and curing new tread rubber, and a final inspection. What comes back is a tire ready to run.

