Triumph TR4

1961–1967 · 68,718 with the TR4A · look underneath first

Michelotti’s body, wind-up windows — and a TR4A that may have independent rear suspension or may not.

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About the Triumph TR4

The TR4 of 1961 brought a Michelotti body with wind-up windows in place of side screens, rack-and-pinion steering replacing cam and lever, and a new all-synchromesh four-speed gearbox. 40,253 were built to January 1965, commission numbers CT1 to CT40304, of which only 2,592 stayed in Britain. 2,138cc is standard and the 1,991cc was a no-cost option for under-two-litre racing classes, so as on the TR3A the commission number tells you nothing about capacity. Front discs are Girling with rear drums, and the disc size changes mid-model — 11in up to CT4690 for wire wheels and CT4388 for steel, 10 13/16in after. Carburettors went from SU to Stromberg late in 1962.

The TR4A is the one that needs checking before you order anything at the back. It arrived in January 1965 with semi-trailing arm independent rear suspension on a new and significantly different chassis — wider by about 22mm, rear track up 13mm, a fixed differential and entirely new rear mounting points. But American distributors wanted a cheaper car, so Triumph offered a TR4-style live axle on leaf springs, fitted to the TR4A chassis with leaf-spring brackets added. It is not a TR4 chassis with a TR4 rear end; it is a TR4A chassis with the old axle bolted in. The factory marked IRS cars with a badge on the boot lid, but badges fall off and get swapped — the reliable check is to look underneath. Coil springs and semi-trailing arms, or leaf springs and a solid axle tube. Nobody knows how many live-axle cars were built; no factory figure exists.

Triumph TR4 — specification & changes within the model

TR4: 1961 – 6 January 1965, 40,253 built, commission numbers CT1 to CT40304. 37,661 export, 2,592 home.
Engine: 2,138cc standard, 100bhp net at 4600rpm, 127lb ft at 3350. 1,991cc was a no-cost option. The commission number does not tell you which.
Gearbox: New all-synchromesh four-speed. Optional Laycock A-type overdrive on second, third and fourth.
Brakes: Girling front discs, rear drums. Disc size changes at CT4690 (wire wheels) / CT4388 (steel) — 11in before, 10 13/16in after.
Carburettors: SU, then Stromberg after late 1962.
TR4A: CTC 50001, 1 January 1965 – CTC 78684, 10 July 1967. 28,465 built. 2,138cc at 104bhp net @ 4700rpm, 132.5lb ft, via an improved head and new exhaust.
TR4A rear suspension — check the car: IRS: semi-trailing arms, coil springs, lever-arm dampers, on a NEW chassis — 22mm wider, rear track up 13mm. Live axle: leaf springs on the SAME new chassis, with brackets added. An IRS badge on the boot lid marks the IRS cars, but badges move. Look underneath: coils and trailing arms, or leaves and an axle tube.
How many live-axle cars: Not established. The widely repeated “about 25 per cent of US cars” has no factory figure behind it, and the commission prefix does not reliably separate them. Check the car, not the number.
Front anti-roll bar: A factory option on the TR4A, not standard. It became standard on the TR6.
Electrics: TR4 and TR4A are positive earth. The TR250, TR5 and TR6 are negative.
Suffix letters: L = left-hand drive · O = overdrive. ICTC = Belgian assembly.