Triumph Speed Twin
Years produced: 1959-1966
Claimed power: 27hp @ 6,500rpm
Top speed: 90mph (est.)
Engine type: 490cc OHV parallel twin
Weight: (dry) 155kg (341lb)
Price then: $710 (approx.)
Price now: $6,000-$15,000
MPG: 50-60mpg

If a bike’s impact on the industry and longevity in production are any measure of success, there are few designs that come close to the 500cc Triumph Speed Twin, the first commercially successful parallel-twin cylinder motorcycle. Almost every major motorcycle manufacturer of its time copied or emulated it, and it remained in production for 28 years.

It’s often said that there’s really nothing new in motorcycling. Most of the “new” ideas that found widespread favor starting in the 1960s — overhead camshafts, multiple valves, electric start — had all been tried before 1920, and usually abandoned because of high cost, poor fuel and underdeveloped metallurgy. The fledgling Triumph Co. actually experimented with parallel twins in the years before World War I, before abandoning its efforts in order to produce the more mundane Model H “Trusty” — the 550cc belt drive, side-valve single that served so well on the battlefield.

Edward Turner, Jack Sangster and Valentine Page
Although the Triumph Speed Twin designer, Edward Turner, started his career as a motorcycle dealer, he had a great interest in designing motorcycles. In the late 1920s, he submitted his plans for a 4-cylinder engine to Jack Sangster, owner of Ariel. Impressed, Sangster hired Turner to complete the design and put the machine into production. The result was the 500cc overhead cam 1930 Ariel Square Four. Turner became Ariel’s rising design star — a situation that did not sit well with chief designer Valentine Page.

Page left Ariel in 1932 to join Triumph, where he continued development of an idea he had hatched at Ariel: Page assembled a promising 250cc parallel twin using one of the two crankshafts from Turner’s Ariel Square Four, then took the idea one stage further, designing a 646cc OHV parallel twin. The design, known as the 6/1, incorporated many significant innovations that would find their way into later designs by other manufacturers, such as gear primary drive, a single camshaft, semi-unit construction, oil tank cast in the crankcase and more. Page’s twin proved powerful and reliable, if overbuilt and expensive to make. A limited number of machines were produced, mostly sold for sidecar duty.

In the meantime, Triumph had foundered. In 1936, arch entrepreneur Sangster snapped up the bankrupt motorcycle business, installing Turner as its chief designer and senior manager, so that he now became Page’s boss. Turner used his design flair to revamp the Triumph range of 250cc, 350cc and 500cc singles (all Val Page designs), giving them smart, colorful finishes and evocative names: Triumph Tiger 70, 80 and 90, the numbers intending to indicate their top speed in miles per hour. (This somewhat fanciful nomenclature later became ever more divorced from reality, ultimately with the T140 Bonneville and T150 Trident.)

After the singles, Turner’s next design was his masterstroke: the 1938 Triumph Speed Twin. Though many have accused Turner of stealing Page’s parallel twin concept, Turner acolytes are quick to point out that Page also borrowed from Turner’s Ariel Square Four. Either way, it was Turner’s genius for what we now call consumer product design that secured the Speed Twin’s success.

To his advantage, Turner was endowed with a number of important abilities: He understood the conservative British motorcyclist, so he designed the Twin to resemble the familiar twin-port single; he had an intuitive flair for what later became finite element analysis, designing parts that were “just” sufficiently strong and durable without being over-engineered; and he was a master stylist. Faster or not, the Triumph Speed Twin looked sleeker, speedier and svelter than its contemporaries. In fact, almost all of the subsequent British parallel twins borrowed at least some of its design themes and motifs.