The bikes are built on the TR Series platform, which already underpins the Speed 400, Scrambler 400, Thruxton 400, and Tracker 400, and are manufactured in India in partnership with Bajaj. The motorcycles will go on sale in late spring 2027, with Triumph promising to announce prices in early 2027. Alongside the T40, the company also revealed dates for three more launches before the end of the year.
Since 1959, every Bonneville has been powered by a twin-cylinder engine, making the introduction of a single-cylinder engine under this name an event in its own right. Triumph has done more than simply fit the Speed 400 with a teardrop-shaped fuel tank. Steve Sargent, the company’s Chief Product Officer, noted that the Bonneville name carries a responsibility to get the model right.
The engine retains the existing foundation: a 398 cc liquid-cooled single-cylinder unit with four valves and dual overhead camshafts, compliant with Euro 5+ emissions standards. For the T40, engineers developed a new cylinder head and a dedicated engine tune. The engine produces around 31 hp (23.5 kW) at 7,000 rpm and 36 Nm of torque at 5,000 rpm. That is almost 10 hp less than the other models in the family, but the power delivery is shifted toward the low and mid-range revs. The exhaust features a “pea-shooter” design, while the idle speed has been lowered to give the single-cylinder engine a more pronounced sound.
The chassis has also been redesigned. The bolt-on subframe used on the other 400 models has been replaced by a one-piece frame designed to accommodate twin rear shock absorbers. Up front is a conventional 43 mm fork with rubber gaiters, rather than the inverted fork fitted to its stablemates. The wheels are wire-spoked, measuring 18 inches at the front and 17 inches at the rear. Braking is handled by 310 mm and 255 mm discs, with ABS. Kerb weight is 191 kg, and seat height is 790 mm, dropping to 770 mm with the optional low seat.
Styling takes its cues from the 1960s. A round LED headlight sits in a distinctive housing, the front fender is mounted on stays, and the two-tone fuel tank features hand-painted pinstriping. The one-piece seat includes a passenger grab loop. The two-tone colour schemes are called Meriden Blue with Tangerine Orange and New England White with Jet Black. The T40 Black comes in matte Pewter Grey and Phantom Black, with black wheels, painted engine covers, and a black exhaust.
The technology, however, is thoroughly modern. The round four-inch TFT display can switch to Heritage mode, which features an analogue-style speedometer. Navigation is included, along with Road, Rain, and Eco riding modes and two customisable modes. The bike also features traction control, cornering ABS, and cruise control as standard. In terms of power, the T40 sits between single-cylinder Royal Enfield 350 models and twin-cylinder 650 models. It is more powerful than the Honda GB350S and Kawasaki W230.
Triumph has also announced dates for its upcoming launches. The Tiger 1200 will be unveiled on October 27. The updated 1,200 cc triple-cylinder model will be more powerful and more refined, while its suspension system, according to the company, will be the most sophisticated in Triumph’s history.
The Street Triple 798 will be introduced on November 17. It will feature a new 798 cc engine developed for the 2027 Moto2 championship season and will be the sportiest model in the range. The Tiger 900 will be unveiled on December 15. It will receive a more powerful engine, an improved chassis, and connectivity as standard. The Tiger 1200 and Street Triple 798 will be displayed at EICMA and Motorcycle Live.