Rob, the F-55 deal originated on the west coast during the SCRA days. When the RC1/2 became the spec tire there were a lot of problems at Manzanita. The RC1 wouldn't last and the RC2 had a tendency to delaminate and throw the tread off the tire. That is when they first allowed the F-55 out of desperation because it was a crapshoot whether or not you could finish the race on an RC2. We did a bunch of tire testing at Manzy with Hoosier and they got the RC2 sorted out but the F-55 allowance stayed on the books. It became pretty rare that you would need one. When they steamrolled SCRA under, the new group's rules became a hybrid of SCRA/USAC rules and the F-55 rule got grandfathered in. I'm sure the issue never came up for the National guys because they didn't have a tire rule prior to this year. I was under the impression that once USAC/CRA adopted the DT-3 that the F-55 was no longer legal. Apparently most everyone else thought the same thing.

I'm not defending anyone's decision here, just giving some background into the F-55 deal.