BTO continued a very busy tour schedule and during the supporting tour for "BTO II", Tim was replaced by Blair Thornton. Thornton had been in the Vancouver-based band Crosstown Bus, which released one album on MCA records. In September 1974, the first BTO album with the modified line-up, "Not Fragile" (a play on the hit album "Fragile" by Yes), was released. It became a huge success, reaching No. 1 on both the Canadian and US album charts. It included the No. 1 single "You Ain't Seen Nothing Yet" and AOR favourite "Roll on Down the Highway". "Not Fragile" remains BTO's top-selling non-compilation album, selling over eight million copies to date.