Jaguar XK150
May 1957–1961 · 12in Dunlop discs, standard · and one windscreen instead of two
This is where Jaguar’s discs arrive — and where the split screen becomes a single curved one.
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About the Jaguar XK150
Twelve-inch Dunlop discs with a Lockheed vacuum servo, on all four wheels, standard. That is the XK150’s headline and it is worth stating firmly, because one widely-read reference says discs were an option that appeared in 1960. The contemporary road test settles it: Motor Sport tested an XK150 in October 1958 and described “12-in. Dunlop disc brakes applied with the aid of a Lockheed vacuum-servo”, with “powerful retardation and complete absence of fade”. Three specialist sources agree. While we are being careful: the XK150 is not the first car with disc brakes — the Citroën DS, the Triumph TR3 and the Jensen 541 all got there first. Its real claim is that it is the first Jaguar road car with four-wheel discs as standard specification, and that is claim enough.
The other defining change is the glass. The XK120 and XK140 split screen is replaced by a single curved wrap-around windscreen — the biggest body-rubber breakpoint in the XK line. The doors are thinner than the XK140’s too, so door seals are not shared either, and the body has a straighter wing line, a widened bonnet, flattened front fender tops, a 16-bar grille and a leather dashboard in place of wood. Mechanically the suspension and steering carry over from the XK140 in principle — wishbones, torsion bars, telescopic dampers and an anti-roll bar at the front, a live axle on semi-elliptic leaf springs at the rear, rack and pinion steering with no power assistance. 9,382 built; the fixed-head and drophead launched in May 1957 and the roadster followed in March 1958.
Jaguar XK150 — specification & changes within the model
- Brakes
- 12-inch Dunlop discs with a Lockheed vacuum servo, all four wheels, standard from launch. Confirmed by the October 1958 Motor Sport road test and three specialist sources. One major reference calls them a 1960 option — that is contradicted and we do not use it.
- The windscreen — the XK glazing breakpoint
- A single curved wrap-around screen replaces the XK120 and XK140 split screen. Nothing about XK120 or XK140 screen rubber helps you here. The doors are also thinner than the XK140’s, so door seals differ too.
- Engines and heads
- 3.4 standard 190bhp, twin SU H6 · 3.4 SE 210bhp, B-type head with enlarged exhaust valves · 3.4 S from March 1958 250bhp, straight-port head, triple SU HD8 · 3.8 from October 1959 220bhp, B-type · 3.8 S 265bhp, straight-port, triple HD8. Head colour is a useful check: B-type is painted, straight-port on the XK150S is pumpkin orange.
- Suspension and steering
- Carried over in principle from the XK140: wishbones, torsion bars, telescopic dampers and an anti-roll bar at the front; live axle on semi-elliptic leaf springs at the rear; rack and pinion, manual only.
- Not the first disc-braked car
- The Citroën DS (1955), the Triumph TR3 (Sept 1956) and the Jensen 541 (1956) all beat it. The XK150 is the first Jaguar road car with four-wheel discs as standard, which is the accurate claim.
- Bodies and dates
- Fixed-head and drophead from May 1957; roadster from March 1958. 9,382 built — 2,265 roadsters, 4,445 fixed-heads, 2,672 dropheads. Production ended late 1960.
- Not claimed
- Whether any XK150 was built with drums. We looked; no source confirms or denies it. And earth polarity and voltage.