Triumph Bonneville - Motorcycle.com

In bringing back the Bonneville, Triumph has recreated the look, the feel and the spirit of our most famous parallel twin while updating the concept. Few motorcyclists will need a reminder that for many years the Triumph Bonneville was one of the stars of the motorcycle industry. The original T120 Bonneville was launched in 1959 as a high-performance, dual-carburetor version of Triumph's existing 650cc twin and named after the record-breaking feats on the Bonneville Salt Flats by Johnny Allen.

"From the outset, Triumph's intention with the Bonneville was to produce a machine that combined the old model's timeless appeal with modern technology."

The T120 was a huge hit for Triumph, especially in the USA, and it remained successful until production ceased in 1983. Triumph is confident the new Bonneville will have appeal across the entire motorcycling spectrum. Naturally they hope that its famous name, classic styling and twin-cylinder character will make it attractive to many of those who have ridden Triumph twins from the past. However, the new Bonneville is also aimed at riders of all ages who are simply looking for an enjoyable, good looking, practical machine with lively performance, pleasant power characteristics and excellent handling. Triumph offers a wide range of accessories to help the new Bonneville owner add a personal touch to the bike or make it an even more practical everyday mount.

Triumph is putting a low sticker price on the Bonneville and are very confident of its future. Triumph spokesman, Bruno Tagliaferri, admits that the bike not sell in the numbers that sportier models might manage. However, he reckons the bike will produce plenty of publicity for the company because it resurrects a name that is so steeped in history. The factory estimates an initial sale of around 5,000 units the first year with perhaps two-thirds of those finding their way to the 'States.

Technical Details

Triumph wanted authentic styling, a parallel twin engine and to replicate as much as practically possible the feel and sound that forged the Bonneville legend. This meant using a 360-degree crankshaft (pistons rising and falling together) and a twin-shock rear suspension system. One of the design team's first tasks was to decide which Bonneville from the past should become the inspiration for the new bike. This was not easy, given that the model spanned almost three decades, incorporating countless styling and technical changes; it is rare for two Bonneville enthusiasts to agree about which was best!

After much debate it was decided that the T120 Bonneville of the late Sixties represented the peak of the model's development, taking into consideration factors including performance, styling and position in the market. The new bike is very close to its forebear not only in its look but also in its geometry and physical size. The main requirement for the engine was that it should have a broad spread of power to give effortless acceleration whether solo or carrying a passenger. Traditional capacities of 750 cc and even the original 650cc were considered before 790cc was chosen. The 86 mm bore size gives good breathing in conjunction with the four-valves-per-cylinder layout while the 68 mm stroke allows a long connecting rod that helps to minimize secondary vibration.

As well as the desired low and midrange performance, the new twin produces a respectable peak power output of 61 horsepower at 7,400 rpm, making this the most powerful production Bonneville yet.

Maximum torque is a substantial 44 foot-pounds delivered at just 3,500rpm. Perhaps the most important statistic is that 90-percent of the engine's torque output is available from 2,750 rpm all the way to the rev limiter.

The new engine is air-cooled like the original, but the new model has twin overhead camshafts instead of the old model's pushrod valve operation. A discreet, frame-mounted oil cooler ensures consistent running temperatures for optimum reliability. Camshaft drive is by chain between the cylinders and incorporates an idler gear that allows the cylinder head to be kept very compact. The engine design team made the new powerplant as visually similar to the old one as possible. The oil drain tube at the front of the engine is designed to resemble a pushrod tube from the old unit. Even the five-speed gearbox is reversed, putting the final drive chain on the right instead of the left. This allows the traditional Triumph twin layout of small triangular engine cover on the right and larger clutch case on the left.

The engine's bottom end was made as compact as possible while incorporating features like twin balancer shafts which were necessary to keep high-speed vibration at acceptable levels. The balancers were tuned to ensure that the solid-mounted Bonneville motor has much of the feel of a traditional 360-degree Triumph twin and is not over-smooth. Naturally, the new bike follows Bonneville tradition in having twin carburetors. These 36 mm units differ from their predecessors by incorporating such modern touches as a throttle position sensor and electric heaters (to prevent icing).

The key challenge facing the Bonneville's chassis team was to provide modern handling and steering characteristics using a very traditional layout. In particular, the chassis brief called for light, easy steering that would make the bike agile around town with a sporty feel and excellent high-speed stability. Although the basic layout of the tubular steel cradle frame is simple, the design was realized using sophisticated computerized finite element analysis to ensure maximum strength with minimum weight. Similar methods were used in the creation of the box-section steel swing-arm which pivots through the crankcases. Triumph achieved excellent results by using similar geometry to the late-Sixties Bonneville. This includes a 29-degree steering angle
and a 19-inch front wheel.

Partly due to the twin's low center of gravity, the bike is very maneuverable without compromising stability. Suspension is tuned to give a sporty feel, yet ride comfort has not been overlooked as it was felt that the Bonneville would be used in a wide variety of roles. The Bonneville's seat is well-padded yet also notably low at 30.5 inches, enhancing the bike's appeal to riders of all sizes. The wheels combine wire-spoke design in 19-inch front and 17-inch rear diameters. They hold modern tires whose grip can be fully exploited thanks to the Bonneville's generous cornering clearance. Brakes were another area where tradition was not allowed to compromise function. Single discs at front and rear, each with twin-piston caliper, give reliable and powerful stopping.

"Style was always a key element of the Bonneville's appeal and that is as true of the new bike as the old."

Features such as the classical Triumph tank badge look as striking now as they ever did. The redesigned speedometer and switchgear add elegance and functionality. Paint work and chrome, applied in-house at Triumph's Hinckley factory, are both deep and thick. The new Scarlet Red paint option, coupled with Silver, matches almost exactly the popular Hi-Fi Scarlet shade of the late Sixties, with Forest Green and Silver available as an eye-catching alternative. As in the old days, the gold pin-stripes are applied by the steady hands of Triumph workers. In this as in so many other respects, tradition lives on in the new Bonneville.