Originally Posted by
Kapusta
Mostly 29". The rest 27.5". At least for non-BSO bikes.
You can still get some good 26" tires, though not the selection of the other sizes.
Currently, Continental still makes the Black Chili versions of Race King and Speed King in 26”. I will be disappointed but not surprised when the time comes that those tires aren’t available in that size. At some point I will probably need to get a different bike that can use the sizes currently in favor.
Otto