Sticky asphalt!
This morning, I rode across a 4 lane road that was in the process of being repaved. I didn't realize it until I got to the other side, but my near new 26 x 2.00 Bontrager H5s got coated with a layer of really nasty asphalt. When I got onto the bike path, a layer of small gravel coated the sticky goop. It's really a mess.
I did a search here on the forum. There's various solvents to try, and the consensus seems to be to let it wear off. But, it's really imbedded into the tread pattern. I tried some gasoline, but I think it's kind of a lost cause. I finally had enough of messing with it, and I ordered a new set of tires.
I'm feeling pretty foolish, but in my 50+ years of biking, nothing like this ever happened. I've learned a fairly expensive lesson. Stay away from paving projects!