50 Years of Triumph Vertical Twins

Story by Graham Clayton// Photos by Graham Clayton
November 1 2008
White Triumph Bonneiville 650 TT

The Great Depression drove numerous motorcycle companies to the brink of collapse. Falling sales, incomes and share values, combined with tight credit, spelled the end for a number of bike builders on both sides of the Atlantic. The Triumph motorcycle company, then 33-years-old, also came close to going under, as its owners were more interested in keeping their auto business afloat, rather than their bicycle and motorcycle operations.

In 1936, Jack Sangster, the new owner of Ariel, purchased Triumph’s motorcycle operations at a bargain price. Sangster then appointed Ariel’s Edward Turner to be the General Manager and Chief Designer of the new Triumph Engineering Company. Bert Hopwood (also from Ariel) was made Chief Draftsman. These two bike designers would play a critical role in Triumph’s future success.

The 35-year-old Turner was known for stylish designs and innovative thinking, but he could also be conservative and reactionary at times. Turner had a gift for reading what the biking public would be attracted to, and for creating stylish designs. He also had a flair for pitching images and coining catchy model names that captured the imagination. One of his landmark designs for Ariel was the ‘Square Four’.

Turner was an ideas guy, while Hopwood was a meticulous designer and technical practitioner. It’s fair to say that the two didn’t always see eye to eye. Nevertheless, their pairing worked wonders for Triumph.

In the mid-1930s, the Triumph line consisted of 250, 350 and 500 cc 4-stroke singles that were known for reliability, but were dated in appearance. Turner’s first task was to make the singles more visually appealing, and also to improve their engine performance. This he did, re-naming the three models as the Tiger 70, 80 and 90 respectively, the number designations being reported optimistically as indicators of their respective top speeds. Introduced in 1937, the new Tiger singles were a hit and sold well.

As a designer, Turner was an outspoken advocate for twin-cylinder motorcycle engines. These he said, size for size, were capable of producing more torque, higher revs, brisker acceleration and less vibration than the single cylinder motor that had become the main design of the British bike industry. Turner’s first new Triumph, introduced in the fall of 1937 as a 1938 model, would prove out all of his assertions.

The ‘Speed Twin’, as the new model was called, was a revelation. Its 498 cc pushrod twin-cylinder engine was actually narrower than Triumph’s Tiger 90 single. It had a 63 mm bore and an 80 mm stroke, push rod actuated overhead valves, a separate 4-speed gearbox and was fitted into the same chassis as the Tiger 90 as a cost saving measure. Girder forks were used up front in combination with a solid rear-end and a sprung saddle. The overall dry weight of the bike was 365 lbs (166 kg). The engine was actually set up in a mild state of tune with a 7:1 compression ratio and a small carburetor that yielded 29 bhp at 6,000 rpm. This was a good power output for that time period.

The ‘Speed Twin’, as its name suggested, was fast, had good acceleration and was markedly smoother than contemporary single-cylinder competitors. Top speeds in excess of 90 mph (145 km/h) were reported by British motorcycle journalists who found the new bike to have good road manners and to be capable of cruising steadily at 70 mph (112 km/h) for extended distances.

Turner’s flair for eye-catching design was very evident in the good looks of the ‘Speed Twin’. It was fast, innovative, good looking and cost only five pounds more than its Tiger 90 sibling. A state-of-the-art road bike at a truly affordable price. Triumph was suddenly well ahead of all other British bike builders who had nothing comparable to offer.

Within a year, Turner introduced a high performance version of the ‘Speed Twin’ called the Tiger 100. This 500 cc sports model developed 33 bhp and could actually nudge 100 mph (160 km/h). These bikes were well received in the US where they proved to be very successful in flat track competition.

The outbreak of World War II in 1939 put Triumph twin development on hold for a while. In November of the following year, Triumph’s Coventry plant was destroyed in the heavy blitz bombing of the city. The company moved production temporarily to Warwick while a new plant was built in the country village of Meriden, just a few miles or so outside of Coventry. The new plant opened in 1942.

Once the war was over, Triumph quickly got back to business developing their vertical twin models. In 1946, Irish racer Ernie Lyons won the Manx Grand Prix on a ‘Tiger 100’, clearly proving the competitiveness of the model. The company offered a competition version of the 500 twin called the Grand Prix, which was a hit with racers looking for an affordable mount.

Meanwhile, Edward Turner was increasingly focusing on the USA market that he believed held all kinds of sales opportunities for Triumph. The word from the United States was that American riders needed more power and more speed. Turner got the message.

By 1948, many of the British motorcycle manufacturers had caught up with Triumph and were offering their own 500 cc vertical twin models, but in 1949, Turner got the jump on the bike industry again with the introduction of the new 650 cc Triumph Thunderbird twin.

This bike was developed for the US market and its Thunderbird name was specifically adopted to appeal to the American psyche. It appealed so much that the Ford Motor Company later adopted the name for their new two-seater sports car.

The 650 T-Bird as it came to be known, was an instant hit. The 649 cc engine with a 360-degree crank that breathed through a single carburetor, was easy starting, smooth running and torquey. It developed 34 bhp at 6,300 revs and was a genuine ton-up bike with a top speed of 103 mph (165 km/h). It was also priced very competitively, a mere ten pounds (US $15) more than the 500 Tiger, with a US market price of about $300.

To demonstrate the prowess of their new bigger twin, Triumph ran three of their 650s for 500 laps at the French Montlhery race course at an average speed of over 90 mph, and then to cement the point, rode them home to England.

The new 650 still had a separate 4-speed gearbox connected to the engine by a single link chain. The chassis employed a single downtube, dual cradle frame fitted with oil-dampened telescopic front forks and Triumph’s less than successful spring-hub rear suspension (good for about one inch of travel). The bike’s headlight was incorporated into an enclosed nacelle with a built-in speedo, ammeter and light switch. This tidy new streamlined arrangement was adopted on other Triumph models as well.

The T-Bird weighed around 380 pounds (172 kg), which was relatively light for its day. The bike was stylish with a good-sized fuel tank and a comfortable saddle that could accommodate two easily. Triumph had raised the bar again, and in so doing, had another bestseller.

The T-Bird was the first motorcycle to appear in a Hollywood feature film with its tank badges in place and exposed. The movie in question was the 1953 flick “The Wild One” in which a young Marlon Brando played Johnny, the rebellious leader of a rowdy motorcycle gang. Brando rode a 1950 Thunderbird in the movie that launched a negative biker stereotype which lasted a good twenty years.

Through the 1950s and into the sixties, Triumph continued to make improvements to the Thunderbird, adding a rear swingarm and twin shocks, a light alloy cylinder head, better electrics and increased horsepower (37 bhp by 1960). One of Triumph’s more controversial improve-ments was the addition of partial rear enclosing bodywork that gave rise to the nickname ‘bathtub Triumph’ due to its appearance.

The fifties would be a great decade for Triumph but in 1951, Sangster sold the company to BSA as a tax management initiative. Sangster maintained his connection with Triumph and by 1956, had become the Chairman of the BSA Group.

In 1951, the Tiger 100 was given an alloy head and other engine improvements. The following year, a T100 was ridden to victory in the 500 Clubman’s TT at the Isle of Man. Triumph followed up on this in 1953 by offering a competition version of the Tiger called the T100C. This replaced the discontinued 500 Grand Prix race model. The T100C was a solid performer with hotter cams, higher compression, twin carburetors and a dual megaphone exhaust that yielded 40 bhp.

This 1951 Triumph T-100 500cc road racer was campaigned by Roy Baumgardner at CMA road racing events from 1956 to 1961, including races at Harewood Acres, Edenvale and Mosport Park.

The company had also introduced an off-road version of its 500 twin called the Trophy for riders who wanted to ride back roads, country trails and go cross-country. These models, fitted with high pipes and increased ground clearance, proved to be competent off-roaders and were chosen as team bikes for entry in the ISDT (International Six Days of Trials).

Turner’s assessment of the US market proved to be accurate. Sales of the 500 and 650 twins in America became increasingly important to Triumph’s overall sales and profitability. The British twins were a popular mount State-side in just about every venue of motorcycle competition including flat track, TT, desert racing, enduros, road racing and drag racing.

In 1954, Triumph introduced a sportier version of the Thunderbird called the Tiger 110. Two years later, a Texan by the name of Johnny Allen road a Triumph T110-powered streamliner to a speed of 214 mph (342.5 km/h) on the Bonneville Salt Flats.

For some reason the FIM refused to recognize this new motorcycle world land speed record, despite having previously approved the timing equipment and measurement process employed.

Triumph got the last laugh on the FIM in 1958, when they introduced a new high performance 650 model at the fall Earl’s Court motorcycle show in London. This was the T120 ‘Bonneville’, named in recognition of Johnny Allen’s achievement.

The ‘Bonnie’ came fitted with an improved dual port intake, twin Amal carburetors, hotter cams and higher compression pistons. The end result was a power output of 46 bhp at 6,500 revs and a top speed of 110 mph (176 km/h).

The original 1959 version of the T120 was a bit of a wolf in sheep’s clothing in that it had a distinct ordinary look to it. Its single downtube frame employed standard forks fitted with touring type fenders, an enclosed nacelle head light and instruments, a standard saddle and other running gear that yielded a hefty dry weight of 393 lbs (178.5 kg), some 18 pounds heavier than the 650 Thunderbird.

By 1960, the ‘Bonnie’ had gone on a diet. It now had a twin downtube frame, slimmer sportier fenders, a separate headlight and instruments, an improved saddle and other detail changes reflective of its top sports model status. The following year Triumph offered an optional performance carburetor kit with chopped Monoblocs and a shared float bowl that boosted the bike’s top speed to 117 mph (closer to the bikes T120 speed claim).

American Bill Johnson ran another Triumph 650 streamliner at Bonneville in 1962, and set a two-way land speed record of 224.57 mph. This achievement the FIM did recognize.

Triumph continued to improve the Bonneville and its other vertical twin models throughout the 1960s. The company introduced unit construction engines in 1963 and the following year they started using 12-volt electrical systems. The adoption of better brakes, better suspension and other upgrades continued to improve the breed.

It’s interesting to note that while the 1960s marked the heydays of Triumph’s twin-cylinder models, the decade also saw the rise of the big four Japanese motorcycle manufacturers whose fast developing and technologically more advanced models would ultimately overwhelm the increasingly dated British design.

This writer got his first ride on a motorcycle in 1965 and bought his first bike the following year. At that time, Triumph’s Bonneville was widely regarded as the king of romp and stomp so far as street bikes were concerned. They were fast, light for their size, reasonably good handling and, in the hands of a good rider, hard to keep up with. Triumph’s twins had become the performance standard against which other bikes were compared.

Triumph continued to tweak their twins in search of more horsepower and even better performance. By 1966, the standard Bonneville was putting out something like 50 bhp, and the firm had introduced a US-market competition-only model called the TT Special. This 350 lb bike, designed for flat track and desert racing, came with open pipes, no lights, put out 54 bhp at 6,500 rpm and was good for 130 mph (209 km/h) top end.

In 1967, Gary Nixon won the Daytona 200 on a twin carb 500 cc Triumph factory road racer. This bike developed 50 bhp at 8,800 rpm and was a rocket. Triumph marked this achievement with the introduction of a new 500 twin for the street, aptly named the 500 ‘Daytona’, which came with twin carbs, larger valves and other performance modifications that enabled it to put out 39 bhp and reach a top speed of 110 mph (181 km/h).

Gary Nixon’s famous #9 Triumph Works 500 Racer took the victory flag in the 1967 Daytona 200. The heavily breathed on racer developed 50 bhp at 8,800 rpm.

That same year, British racer John Hartle won the Production TT at the Isle of Man on a 650 Bonneville. This was just one of a whole list of production and endurance racing victories that were racked up by Triumph riders in different events. Triumph released a specially prepared production racing Bonneville called the ‘Thruxton’, so-named in recognition of the many race victories achieved by 650 Triumphs at that famous British circuit.

In 1969, British racer Malcolm Uphill became the first rider to lap the Isle of Man at 100 mph on a production bike, a 650 Bonneville. In addition to winning the Production TT that year, Bonneville riders also took five of the first seven places in the Brands Hatch 500 Mile Race, and won the gruelling Barcelona 24-Hour endurance race in Spain. This was the 650 Bonneville at its peak.

From 1970 onward BSA-Triumph focused their road racing hopes and their big bike sales campaigns on their new 750 cc triples. The twins continued to evolve with assorted detail refinements, but now took a back seat to the multi’s.

A new frame that incorporated an oil tank inside its frame tube was introduced in 1971, but it was widely criticized for being too tall (34” saddle height). A lowered version was introduced in 1972, and later that year, the 744 cc T140 Bonneville was launched, complete with 5-speed gearbox and a front disc brake.

BSA-Triumph was in serious financial trouble by 1973, and in order to secure government assistance, it merged with Norton-Villiers to form NVT. A plan to transfer the three-cylinder Trident production to BSA’s Small Heath facility, ceased twins production and closed the Meriden factory and led to a sit-in and plant seizure by the Meriden workers. This lasted from the fall of 1973 until March 1975. In the end, a Workers Co-Operative was established, with UK Government assistance, to resume production of the Triumph twin-cylinder models.

The co-op would soldier on building twins until August of 1983. Their bikes included a number of improvements such as disc brakes front and back, aluminum spoked-wheels, electric starters and other refinements.

Initially they built single and twin carb versions of the 744 cc Bonneville twin. Later, however, they added a dual-purpose model called the Tiger Trail, and an economic short-stroke 650 called the TR65 Thunderbird. There were several unsuccessful efforts to develop new and improved models, but the co-op was always cash-strapped. Ultimately the co-op simply ran out of money.

That year, 1983, self-made British multi-millionaire John Bloor purchased the rights to the Triumph motorcycle name. He granted Les Harris a license to produce and sell twin-cylinder Triumph parts and complete motorcycles through his Devon-based firm, Racing Spares, for a period of five years. These bikes were the so-called ‘Harris Bonnevilles’, the last of which were produced in 1988.

Fifty years after the introduction of Triumph’s groundbreaking ‘Speed Twin’, it was all over, and another chapter ends in Britain’s long and storied motorcycle history.


Copyright ©2002-2024 Motorcycle Mojo | Privacy Policy | Built by Gooder Marketing