^ what he said.
"some" new tires are a bit slippery at first. Folks used to say it was do to the release agent the maker used to pull the tires from the mold. Bike tire makers tell us they don't use any release agents.... But new rubber is very smooth and can have less grip than the same tire after 100 miles of riding.
So... To be safe , take it easy as suggested for at least 80-100 miles.