The Triumph TR4 was a British sports car produced by Standard-Triumph (a division of the Leyland Motors group) from 1961 to 1965, with some models registered into 1966 and early 1967. Designed by Italian stylist Giovanni Michelotti, the TR4 was a significant evolution of the earlier TR2/TR3 series.

The IRS in “TR4 IRS” refers to the Independent Rear Suspension, introduced in 1965 with the TR4A variant. This model replaced the earlier live rear axle setup with a more refined independent rear suspension system, improving ride comfort and handling. The full designation was TR4A IRS, though not all TR4As came with IRS – some lower-cost versions retained the solid rear axle, especially for certain export markets.

Key Features of the 1966 Triumph TR4 IRS:

• Engine: 2.1L (2138 cc) inline-4, producing around 105 hp
• Transmission: 4-speed manual (optional overdrive available)
• Suspension: Independent rear suspension (IRS) with coil springs (for IRS versions)
• Brakes: Front disc brakes, rear drums
• Body: Steel body with aluminium bonnet and boot lid
• Interior: Minimalist but sporty, with wood dash and classic Smiths gauges

Notable Innovations:

• First in the TR series with roll-up windows (previous models had side curtains)
• Optional Surrey Top, a hard rear window with removable centre panel (a precursor to modern T-tops)
• Improved comfort and handling compared to its predecessor

Production Info:

• Approx. 28,465 TR4As produced (1965–1967)
• Around 75% were IRS models
• 1966 was a peak production year, making the 1966 TR4A IRS one of the most common variants

The TR4A IRS has since become a sought-after classic, valued for its blend of 1960s British style, Michelotti’s timeless design, and improved drivability due to the independent rear suspension.