Triumph Speed Twin
Triumph Speed Twin Background & History
The Triumph Speed Twin was a product of the times, and yet a game-changer. Throughout the 1920s and 1930s the British motorcycle industry, the largest in the world at the time, with a few notable exceptions, settled on the 4-stroke, air-cooled, single-cylinder as the engine architecture of choice. Nearly every manufacturer had one, or several, and they were usually their best sellers. Vincent may have built the sexy V-twin Black Shadow, but they made their money by selling lots and lots of single-cylinder Vincent Comets. Ariel is famous for their brawny Square Four, but their biggest seller was the single cylinder Red Hunter. Single cylinder bikes of this mold were widely understood by the engineers who built them, and widely accepted by the buying public. Displacement and horsepower output grew steadily through the 20s and 30s and by 1935 or so, most had generally capped out at about 500cc and 23 hp or so.
The 1938 Triumph Speed Twin was one of the most pivotal bikes of its time. It ushered in the era of the vertical twin that lasted until the 1970s. All pre-war Speed Twins used girder front forks.
The Vertical Twin
The problem with big singles has always been engine vibration, enough in those days to destroy and engine in seconds. To pull make more power, the engines would have to rev faster, which led to ever more vibration. To add displacement also added weight (ie: larger pistons and rings and/or bigger crankshafts), which added to the vibration problem. Many solutions were tried, but nothing seemed to work. When Ariel Motorcycles bought Triumph in 1936, he put one of Ariel’s top engine designers on the task of sprucing up Triumph’s lackluster product line. Edward Turner was fresh off of designing the first Ariel Square Four and he quickly put together an engine design, the ‘vertical twin’, that seemed to do all things: 1.) Drastically improve on the engine vibration problem; 2.) Made more power and torque, and wound higher than the big singles; 3.) The new engine utilized primary drives, clutches, gearboxes, frames, etc. from their existing inventory of singles parts; and 4.) The twins used much of the same tooling and manufacturing methods as the singles, greatly simplifying production.
The 500cc Triumph Speed Twin engine was designed to fit into the spot where there single-cylinder engines went. It kept things simple and save them money.
Triumph Speed Twin Beats Vibration
This was accomplished by breaking that 500cc of displacement typical of the big singles of the day into two cylinders, each rising and falling together on a 360-degree crankshaft, but firing alternately. Where the 500cc singles only had a power stroke every other engine revolution, the vertical twins produced one power stroke every stroke, smoothing out the power delivery which greatly improved the engine vibration. Triumph Motorcycles introduced their revolutionary new 500cc vertical twin in an entirely new line of bikes: the 1938 Triumph 5T Speed Twin.
This 1948 Triumph Speed Twin shows the post-war pattern: telescopic forks and a rigid frame with a solid rear hub, rather than the 'sprung hub' that the other twins had since 1946.
Prewar Triumph Speed Twin
These early Speed Twins were fairly simple for Triumph to produce, because the primary drives, the gearboxes, the frames, forks, wheels, tires, brakes and running gear were all straight off of the Triumph singles line. The new engine was designed to bolt directly into the same frames that Triumph’s singles used. It was pure genius. The Speed Twin initially came in one color, Amaranth Red with gold pinstripes against chrome. They were practically art deco pieces. All pre-was Triumph Speed Twins came with girder front forks and a rigid frame with a sprung seat for some cushion.
This 1956 Triumph Speed Twin was the first year for the swing arm rear suspension. The rest of the Triumph line got it in 1953.
Triumph Speed Twin Leads the Way
The Triumph Speed Twin was a huge hit for Triumph Motorcycles, and almost the entire rest of the British motorcycle industry (those who could afford it, anyway) rushed their own vertical twins to market. However, World War 2 started in 1939 and civilian production halted until 1946. But, when it resumed, the business just took off, with Triumph in the lead, thanks to the Speed Twin, and it’s new hot-rod stablemate, the Triumph T100 Tiger, launched in 1939. Civilian production resumed after World War 2 in 1946, and by 1949, BSA, Norton, Matchless/AJS and Royal Enfield all had their own 500cc vertical twins. So, in 1950, Triumph Motorcycles bored and stroked out the 500cc to 649cc and the Triumph 650 was born in the 1950 Triumph 6T Thunderbird. By 1954, they’d applied the same ‘Tiger treatment’ (ie: hotter cams, higher compression and a bigger carb) to the new 650 to create the Triumph T110 Tiger. Then, in 1956, a new alloy cylinder head called ‘the Delta head’ led to a new bike, the 1956 Triumph TR6. Then in 1959, Triumph added a second carburetor to the TR6 engine, creating an even hotter new model, the 1959 Triumph T120 Bonneville. With all of this upmarket action, the venerable Speed Twin became Triumph’s entry-level twin and as such, it wasn’t given some of the features of the higher-end bikes, like the sprung rear hub which was introduced into the rest of Triumph’s lineup in 1946, but the Triumph Speed Twin didn’t get it until 1952. And when the rigid frame was retired on all other Triumph twins in favor of a swing arm rear suspension in 1953, it took until 1956 to get to the Triumph Speed Twin. All in the interest of keeping the costs down on their cheapest twin.
This 1964 Triumph Speed Twin shows how Triumph shrank the bathtub bodywork more and more each year to satisfy the American buyers who hated stuff like that.
Triumph's Bathtub Bikes
When Triumph’s 500 twin went to unit-construction in 1959, the Speed Twin benefitted from this lovely new powerplant and an all new frame. The Triumph Speed Twin, different than the rest of Triumph’s line (excepting the 350cc Triumph 3TA Twenty One), meant to be a cheap commuter bike for the British home market was outfitted for the foul riding weather typical of England. The Speed Twin got and ungainly full-coverage front fender, another headlight nacelle (it always had one of those) and a rear enclosure nicknamed ‘the bathtub ‘. In England, riding conditions are often rainy, muddy and foggy, and rust was a big problem. British riders were accustomed to wiping their bikes down after every ride. These ‘Bathtub bikes were meant to be an answer to that problem. They were supposed to keep the moisture out and thus be easier to clean up. However, the water still go into every nook and cranny and now sat unnoticed inside the bathtub until it rusted all the way through. A very typical problem with Bathtub Bikes. While the Brits liked it, US buyers hated it. The scrappy Brits rode in all weather, but most Americans only rode in good weather so there was no advantage to it, real or perceived. Few were sold here, and many got their bathtubs swapped out for bodywork off to Triumph’s other 500 models. In response, and starting in 1962, Triumph began reducing the size of the bathtub until it finally disappeared altogether in 1966, the Triumph Speed Twin’s last year in production.
The 1966 Triumph Speed Twin showed how the bathtub bodywork had completely disappear by the model's final year in production.
Triumph believed that the Speed Twin was competing with other models in its one product portfolio, in other words it was competing for the same buyer. And the other models were more profitable than the low-cost Speed Twin, so it was cut, replaced by the Triumph T100C Trophy.
This 2019 Triumph Speed Twin is a thoroughly modern bike in every way. And now built with work class reliability and performance.
Triumph Speed Twin in Modern Times
The name Triumph Speed Twin is being used in modern times by the new Triumph organization, raised from the ashes of the failed Meriden-based Triumph Engineering and subsequent Meriden Workers Co-Op when the lights went out in 1983. It took until 1989 to start building modern Triumph’s at the new Triumph factory in Hinkley, England. Hence, all classic Triumphs are known as Meriden Triumphs, and all modern Triumphs are known as Hinkley Triumphs. Triumph Motorcycles has revived the Triumph Speed Twin name and they’re stunning machines. 1200cc twin, SOHC 4-valves-per-cylinder, 270-degree crank, fuel injection and 100hp. The new Triumph organization is on a roll, building a fleet of world-class motorcycles which compete in a wide range of markets. Good for them. They've revived the great Triumph brand into something every Briton can be proud of.
Triumph Speed Twin Books
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By Lindsay Brooke, 192 pagesTriumph's dominance of the US motorcycle market, lively text, hundreds of historic images. |
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By Timothy Remus, 144 pagesDetailed anthology of all classic Triumph motorcycles, illustrated. |
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