Bet won for Tucson: the BT 5.50 weighs the weight of a GP 250 !

Arousing curiosity and admiration, the project of Jean-François Robert and Yann Bakonyi has come to an end: to design from scratch the most efficient motorcycle and especially the lightest possible to go and tease the big bi in Top Twin !

At the origin of this somewhat crazy challenge, the experience and talent of Jean-François Robert, a true wizard of motorcycle mechanics, convinced of the superiority of a light motorcycle and usable on a large displacement admittedly more powerful, but also heavier and less handy…

How much does it cost to create a motorcycle ?

"Without having evaluated it with complete accuracy, the manufacture and development of a 100% original machine, ready to run, with top-level equipment (brakes, rims, tires, suspensions, engine preparation, shifter, etc.) as well. that a chassis and a personalized covering must be close to 100,000 €", explains Jean-François Robert on the official Tucson website. Among other things, the Paioli fork of GP costs 4,500 € HT without the tees, the engine budget reaches 30,000 €, the Bridgestone train costs 271 € HT and the kit Beringer brake exceeds € 2,000…

The hunt for superfluous bulges !

Passionate and persevering, the man created Tucson in 1994 and manages – despite limited means – to design and run motorcycles as light as technologically daring as the Veloce, a 170 kg proto powered by a Suzuki SV engine. !

To push his approach to its climax, this former engineer launched the Superleggera BT 5.50 project last spring (read): a 100% original motorcycle built around the 77 ° V-twin of the Aprilia 550 SXV (read our).

A real technological and sporting challenge, this thin blade designed by Yann Bakonyi must not exceed the quintal and will defend the validity of its concept through the Top Twin championship, races reserved for twin cylinders capable of cubing up to 1200 cc! Based on the speed of passage in higher curves and the lower aerodynamic drag of its creation to compensate for a power more than twice lower than the Ducati 1098, KTM RC 8 and other Buell 1125 R (read our), Jean-François Robert knew seduce renowned technical partners to set up your project (see box) and start hunting for superfluous grams…

A salivating technical sheet

On the engine side, Tucson is delighted with Aprilia’s support and responsiveness: "never have we had such help from a manufacturer to date !", concedes Jean-François Robert in view of the performance and measured weight of the Aprilia bi. Weighing only 33.6 kg with the injection bodies, the 549 cc block thus arrived fitted with camshafts VDB, a shifter, a titanium exhaust line, a clutch with torque limiter STM and a minimalist 2.3 Ah battery.

As on the Veloce, the airbox is located just above the engine and is supplied by a direct dynamic air intake, thanks to the absence of a steering column. A self-supporting aluminum tank in a central position acts as a saddle support, a technical choice which allows "both eliminate the rear loop of the frame and better center the masses", explains the manufacturer.

A fundamental point in the realization of the concept: not only the motorcycle must be as light as possible, but its distribution of the masses was the subject of long hours of reflection to grant to the BT 5.50 an ease of piloting and an optimum efficiency. Thus, the oscillating arm axis passes directly into the foundry of the V2, as on MotoGP Ducatis: a certain weight gain, but also a good way to lengthen the swingarm as much as possible – to gain traction – without increasing a wheelbase that Tucson announces at only 1300 mm !

Produced by Technitubes, the frame measures only 22 cm in its upper part and weighs only … 4.1 kg! Its efficiency is supported by Paioli suspensions straight out of the Grand Prix paddocks: the fork is pressurized and weighs only 5.3 kg without the tees, elements that Tucson had machined and announced at 500 g each. The shock absorber comes from the same supplier and has a wide range of settings, but above all its aluminum body allows again to contain its mass below 3 kg !

The complete covering is signed Artytech and weighs less than 3 kg without the imposing bubble which promises upper body protection worthy of a GP machine! A timely comparison, since the BT 5.50 would weigh only 96 to 97 kg (with oil, water and a little gasoline) of which more than 50% distributed on the front: a measure to be confirmed "officially" but that we can already approach 98 kg of the official Aprilia 250 of Alvaro Bautista !

Finally, to slow down the ardor of this tiny machine (Tucson specifies that many bikers have compared it to a 50 cc!), The manufacturer Beringer provides a latest generation single-disc cast iron assembly clamped by a radial caliper, whose weight total (excluding rear disc, brake fluid and hoses) is only 3.99 kg! A device a priori sufficient to stop the BT 5.50, whose top speed is still estimated at nearly 250 km / h !

The bike is now complete, the next step is to lovingly prowl the Aprilia engine before starting the driving sessions to define the first bases of adjustments. Anyway, the work and tenacity of the team already command respect and we dream of seeing this Tucson revolve around big twins next season … Stay tuned !

Alexandre BARDIN – Photos DR

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