The first variant of the Triumph TR4 was the standard or Base Model. Debuting in 1961, the TR4 was offered in a convertible body style, although an attachable hardtop (Surrey-Top) was available. These cars were powered by a 2.2L inline four engine that sent drive to the rear wheels through a 4 speed manual transmission. While achieving moderate success, the TR4 was criticized for its ride, so in 1965, an updated version of the TR4 known as the TR4A (IRS) was introduced.