Triumph Speed Twin
The model that brought twin-cylinder motorcycling to the masses – and set the template for Triumphs for decades
It’s impossible to overstate the importance of the Edward Turner-designed Speed Twin – both to Triumph and motorcycling in general. Although it might not be Triumph’s first twin – that accolade goes to the 6/1 of 1934 – the 1938 Speed Twin (actually announced in late 1937) was the first multi-cylinder bike for the masses. There had been twins before, of course, like Vincent’s exotic and expensive V-twins – and even fours, like Ariel’s Square Four. But they were priced far out of the reach of the ordinary man and, while the 6/1 lasted a mere three years and was a resounding commercial failure, the Speed Twin’s overhead-valve paralleltwin engine created a template for the British motorcycle industry that would endure for the next 40 or so years.
The pre-war Speed Twin was certainly a revelation. Fast, smooth and reasonably affordable, it pointed the way forward for Triumph – as well as its competitors. The initial success of the model prompted all Triumph’s major rivals into developing their own parallel twins, but the outbreak of World War II in 1939 put paid to their plans and the production of the Speed Twin until 1946. It was after the war was over that the Speed Twin really came of age. Quite simply, it was the most important component of Triumph’s success as a motorcycle manufacturer in the post-war era.
With the exception of the Tiger Cub and oddments like the Tina scooter, pretty much all of Triumph’s post-war motorcycles are based – to a greater or lesser extent – on Turner’s original Speed Twin.
EDWARD TURNER TURNER’S GENIUS CREATED A BIKE THAT WAS COMFORTINGLY FAMILIAR WHILE BEING RADICALLY DIFFERENT
Part of Turner’s genius in creating the Speed Twin was the fact that it was comfortingly familiar to the conservative British motorcyclist while being radically different under the skin. The rigid frame, girder forks and the instrument console inset into the top of the fuel tank were features shared with Triumph’s single-cylinder Tiger 70, 80 and 90 models. Even the engine didn’t look radically different to the twin-port singles at first glance. For a start, it was a commendably slim unit – thanks in part to Turner’s design, incorporating two main bearings and a 360° crank. It also used the traditional Triumph formula of gear-driven camshafts with pushrods actuating the overhead valves, a chain primary drive to a separate four-speed gearbox, and cast iron barrel and head (with detachable alloy rocker boxes). Ignition and electrics were taken care of by a Lucas Magdyno unit mounted behind the cylinder barrels. In short, it was a canny fusion of the old and the and the new – and allowed Triumph to use as many existing parts as possible while making the most of the ground-breaking twin-cylinder engine. A measure of just how good the Speed Twin proved to be, is that it stayed in the Triumph line-up until the 1967 model year. That’s an impressive 30-year production life. And, even then, the model that replaced it – the ‘standard’ Tiger 100 – was virtually identical, though that only lasted one more year in the line-up. During that long life, the Speed Twin evolved while retaining its essence. For the 1939 model year, it got the eight stud barrel fixing debuted on the new Tiger 100 sports variant that same year. But, from then until production ceased for the duration of the war, there were only minor revisions to the new twin.
When production resumed after the war in a new factory – Triumph’s Coventry plant had been destroyed by bombing in November 1940 – the Speed Twin reappeared wearing telescopic forks and a 19in front wheel replacing the earlier 20-incher. A separate dynamo (replacing the previous combined Magdyno unit) was mounted at the front of the redesigned crankcases, while a BTH magneto provided the sparks. And more was to come.
Triumph’s sprung hub, which provided around two inches of suspension movement for the rear wheel via an ingenious sliding spindle arrangement with springs above and below the spindle, allowed the rigid frame to be retained and was offered as an option for 1948. The following year saw the adoption of the Triumph ‘nacelle’ headlight surround and a new fuel tank with the instruments moving from the top of the tank to the nacelle.
For 1950, a new, painted tank with the familiar horizontal chrome strips along the side replaced the previous chromed version. A larger seven-inch headlight was introduced for 1952 and machines for the 1954 sales season were equipped with alternator electrics and coil ignition. The Speed Twin was moving with the times...
For the 1955 sales season, it moved another big step
forward with the introduction of a swingarm frame – though rigid and sprung-hub models would remain on sale for some time. Conrods and crank bearings were upgraded for that year, too, and a dual seat became the default option for the Speed Twin. In 1956, the 500 was fitted with the same crankcases as the 650cc 6T models.
In 1957, the Triumph ‘mouth organ’ tank badge appeared, though a more significant change was, perhaps, the unloved Slickshift gearbox adopted for 1958. Then in 1959 the biggest change of all occurred, with the appearance of a new shorter-stroke, unit-construction engine for the Speed Twin – and a change of model designation to the 5TA. There was a new frame, too and, more obviously, the infamous ‘bathtub’ rear enclosure. By 1964, the all-enveloping bodywork had been trimmed back a bit, replaced by the so-called ‘bikini’ enclosure. The hated enclosure was gone by 1966 – but it was too late to save the Speed Twin; the model was pensioned off at the end of that year. Nonetheless, it remains one of the most significant and important models in Triumph’s illustrious post-war history.
It was during the immediate post-war period that the Speed Twin really helped to put Triumph back in the limelight – so the chance to take a ride on a 1949 model (courtesy of the pre-unit Triumph specialists and arch enthusiasts at Ace Classics in South London) seems too good to pass up on. And so, on one of the hottest days of the year so far, I find myself following Kev Rushworth’s van out into Kent to sample the Speed Twin experience. Kev – the younger half of the father and son duo who run Ace Classics – has persuaded dad Cliff to look after the shop while he transports one of their collection of Speed Twins out of the capital’s traffic-clogged streets to give me a more pleasant riding environment in which to enjoy the 73-year-old groundbreaker. Thanks, Kev.
As Kev and the van disappear down the road, I can take in the classic lines of the Speed Twin. The bike was bought by Kev and Cliff at a Kempton Park autojumble some time ago. It’s an earlier restoration by the look of it and, while it arrived in the Ace Classics collection wearing a 1950 tank, it was in pretty good shape according to Kev. With the correct chromed tank, a pair of higher-rise Us-market handlebars and a single saddle fitted, the bike was good to go – and now I’ve got the chance to see just how good that go is.
Kev says: “Edward Turner certainly had an eye for style. This is one good-looking motorcycle. Tele/rigids have a real look to them and the Speed Twin is no exception.” The Us-market ’bars suit the bike perfectly in my eyes, and the clean, uncluttered lines and understated Amaranth Red paintwork combine perfectly. If the bike rides as well as it looks, I’m in for a treat.
Fuel on, a light tickle of the Amal Type 276 carburettor, a gentle swing on the kickstart and the Triumph rasps into life. The engine doesn’t take much warming up in this weather and, in a matter of a minute or so, I can snick the gear-lever down into first and start to enjoy high-tech motorcycling 1949-style.
It’s easy to forget how smooth, forgiving and fun to ride a 500 twin can be. And this Speed Twin, despite its age, feels right up there with the best. Pulling away, the clutch is light and smooth, and when changing up through the gears each shift is crisp and positive.
It’s the same on the way back down the ‘box. Rolling off the throttle for a tightening bend, I click down into third
as easily as I would on many much more modern bikes. It helps, of course, that this bike has been through expert hands in Ace Classics’ workshop – it’s apparently a machine that Cliff rides fairly frequently – but it’s also a reminder of just how sophisticated the Speed Twin must have seemed back in the ’40s.
With a fairly soft 7:1 compression ratio and relatively mild cam profile, the Speed Twin engine is no firebrand – but neither is it a slouch. And, if you wanted the ultimate sporting 500 twin in 1949, you’d have probably gone for the Speed Twin’s Tiger stablemate anyway. Acceleration is brisk and the engine feels delightfully smooth and quiet as I thread my way along some surprisingly quiet Kentish lanes just a few miles from the bustle of South London and the South Circular Road that passes Ace Classics’ shop window. I could be in another world – or back in the world when the Triumph rolled off the new Meriden production line back in 1949 – and it’s one where the Speed Twin feels right at home.
The combination of the rigid frame and the optional sprung hub works better than I expect, too. Wear in the undamped sprung hub can precipitate wayward handling, I’m told, but this one is obviously in good order and provides adequate relief from the worst of the ripples and dips in the road surface, while the forks are unobtrusively competent. Sure, I’m not pushing the Speed Twin to its limits, but nonetheless the ride is certainly brisk enough to be entertaining and engaging on the narrow lanes. On some machines of this age, brakes can be something of an optional extra, but not so with the Speed Twin – or this example, anyway. The seven-inch drums might not have the bite of a Tickle tls unit, but they’re more than up to hauling up the genuinely middleweight 361lb (163kg) of the bike – at sensible speeds, anyway. In just about every respect, the ride this bike provides is the equal of the visual impact Turner’s inspired design delivers. And in my eyes, the post-war tele/rigid incarnation of the bike is the best balance of design and practicality. The classic lines of the rigid frame whether with a sprung hub rear wheel or not – the neat, functional forks and elegantly purposeful engine combine to create the epitome of what a ’40s bike should look like. The smooth power of the Speed Twin must have been a revelation to a generation largely brought up on big, thumping singles. There’s no doubt that Turner’s masterpiece was a game changer in its day. And, after spending the day on this wonderful survivor, I’m convinced it remains relevant today. The basic design of the Speed Twin engine would power virtually all of Triumph’s middleweight and heavyweight bikes until the launch of the Trident in 1968. It’s an impressive legacy. The Speed Twin hasn’t just stood the test of time – it’s passed it with flying colours.
KEV RUSHWORTH ‘EDWARD TURNER CERTAINLY HAD AN EYE FOR STYLE. THIS IS ONE GOOD-LOOKING MOTORCYCLE’