Two Wheel Drive (from the
web)
The sandy and rocky tracks of the Moroccan desert proved an ideal testing ground for Yamaha's 2 wheel drive rally bike. French enduro rider David Frétigné won the rally and Jean- Claude Olivier, President of Yamaha Motor France, scored second.
Yamaha is just about to change the future of motorcycle rally machines. Just like the 4 wheel drive rally cars a few years ago, the WR 450F 2-Trac demonstrated it's winning potential. It may seem obvious, that an all wheel driven vehicle would be superior on slippery or sandy surface. Nevertheless the technical development regarding weight, compactness and reliability is a big challenge and Yamaha is the only manufacturer to apply the 2 wheel drive technology to it's off road rally machines!
Jean-Claude Olivier recalls: "Riding the WR 450F 2-Trac you will be amazed by its ability to perform in such difficult conditions like deep soft sand (or mud). The bike still goes on when standard bikes are digging themselves holes to get stuck. You also will realise quickly that the 2-Trac motorcycle has a much higher steering stability, both in a straight line, and in corners. It feels a bit like carved skis, you can lean into corners and the rear part of the bike takes up the same track easily, without sliding. It makes riding much more relaxed when you don't need to counter steer."
There is even an advantage for "normal" motorcycles Jean-Claude Olivier adds: "I guess that the advantage of a two-wheel drive must be even bigger for beginners than for experts. Just lean into the curve and the rear part of the bike automatically takes up the same track. You get quickly used and riding becomes quite natural. The 2-Trac system makes braking safer and easier: the bike stays well in line during braking. The rider does not need to brake in curves, but can brake stronger and later before cornering.“
Controllable power.
Since the rider does not need to counter steer and can avoid rear wheel slides, control of power becomes much easier. Unlike a conventional motorcycle where even an experienced rider will fight with a sliding tail end, the 2-Trac is much more controllable. All you need to do is lean into a curve, the bike will follow your command precisely and stays perfectly in the desired line. An exciting efficiency and directness!"
How 2-Trac works:
Unlike the drive systems we are used to on motorcycles, 2-Trac features a hydraulic drive to the front wheel. As Lars Janson explains in his interview, the Yamaha patented system uses a hydraulic pump located on top of the gearbox and driven by a chain in an oil bath which actuates hydraulic fluid via high pressure hoses to the front wheel. The special hub in the front wheel is a "hydraulic motor" which is set in motion through the pressure of the hydraulics. This construction allows a "smart operation": the pressure, and consequently the pulling power on the front wheel, varies the more the rear wheel slips. The system can regulate itself and always applies the best ratio of power between the front and rear. You can also adjust the system, depending on usage of the machine, and apply more basic thrust up front, or less.
The performance edge:
Jean-Claude Olivier confirms: "Öhlins (who developed the system) has done a great job. The bike now is really reliable. Both David Frétigné and myself have had no transmission problems whatsoever during the
entire rally. The latest version of the 2-Trac system has seen lots of improvements. You don't feel any overweight on the front wheel and you get used to the machine right away.
The top speed of a WR 450F 2-Trac on a sandy track is about 10% higher than its conventional counterpart due to improved traction."
Yamaha has now successfully passed the first step of its 2-wheel drive system evolution. 2-Trac has proved its efficiency in the most extreme conditions. It has become light, compact, elegant and is well integrated in the bike's design. There is no comparison to the complex mechanical systems seen in the past." 2-Trac is an integral part of the WR 450F rally bike.
2-Trac in the future
It will still take a while until 2 wheel drive makes its way into mass production. Jean-Claude continues: "I can imagine such a system fitted on any kind of off road motorbike, or even scooter or road bike. Two-wheel drive would be beneficial on a large Grand Tourer or scooter for example, since you could combine high power in an integral transmission with coupled braking, to offer the ultimate safety both for experts and, in particular, for novice riders."
In fact two-wheel drive transfers power to the front wheel when the rear wheel may start to spin, and is
therefore a very effective anti-slip device that can handle large power and slippery surfaces.
See the Yamaha web page for
more info and great pictures …Ed.