Without tubes my tires always rubbed. With tubes the tires never rub. The ET difference may have to do with the way a tube will stiffen the sidewall and change the contact patch more than anything.

1967 Coronet, 1989 Daytona tube chassis. Former cars, 66 Charger, 67 R/T, 69 Coronet, 67 Dart GT. -Banned for life from V8Buick.com-