I have done that road a dozen times. And the dirt road just north of it on a Versys. That is where Lewis and Clark crossed The Bitterroots. It was on Hy 12, on a Honda VTX 1800 with a car tire, I came upon a young fellow on a SV 650. The old fart on the VTX taught the youngster a lesson on high speed sweepers. He finally caught me at a gas stop Kooskia where he promptly got in face screaming. "You stupid old man you can't run a square tire on a motorcycle" I told him you didn't stay long in my mirrors punk. He just got madder and madder.
I just laughed at him whilst holding my helmet as a weapon in case he wanted to escalate this discussion further. He left with his tail between his legs
Gawd I miss that old VTX. It was a great ride and it took me so many places and met so many interesting folks. Square tire and all