Scraping a racing tire - GIF

[Frank S]

The people that did that are no longer with us...

A lot of tires clearly state on the sidewall as being regroove-able What they don't mention is the maximum depth the grooves should be cut to. It requires someone who knows what they are doing to regroove a worn tire properly adding a few more miles of safe useable wear.
The same thing goes for branding truck tires. "NEVER" brand an inflated tire and only brand in the designated area cast into the sidewall