the rack is not susposed to be threaded!! atleast the bottom one at the dropout, the screw goes through it and and screws into the frame.
I am not familiar with that rack. are the upper holes threaded?
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk