Here is the complete fix: select the two edges and delete them.
Duplicate the treads and move the duplicates up. Shift R to repeat that (so the moving distance will be the same as the first time).
Connect those pieces like so:

Make two straight cuts to make one segment and remove the unnecessary vertices:

Don’t forget to set the Relative Offset back to 1:

Still needs some topology cleanup, but it’s a gap-less tyre at least;)