August 22, 2007 Four Wheel drive cars have taken over at the top-level of off-road rally racing, but dirt bike racing is still predominantly fought out on single-wheel-drive vehicles that spin up, fishtail and slide wildly across rough terrain. Make no mistake though, the All Wheel Drive (AWD) revolution is coming to the motorcycle world – Yamaha and KTM have done significant work with hydraulic front-wheel-drive systems, and when new ideas like this successful all-mechanical AWD kit from Christini hit the mainstream, dirt bike riding will never be the same again.
AWD cars are extremely popular and sell at a premium despite the fact that the vast majority of drivers very rarely make use of the advantages they offer in low-traction situations. Dirt bike riders, on the other hand, constantly struggle for traction from the moment they take off, spinning the rear wheel and sliding the front as they battle the roughest terrain they dare to – and yet Yamaha and KTM are the only manufacturers to have had a serious look at driving the front wheel of a motorcycle, with mixed results. While the hydraulic system on the Yamaha received high praise for its handling, climbing and traction advantages, it sapped significant power from the rest of the bike, leading to lukewarm reviews.
Market minnow Christini has come up with a new system that suffers virtually none of the power loss of the Yamaha and KTM’s hydraulic systems. Using a set of gears and drive shafts mounted through the frame, triple clamps and forks, Christini claims they have developed a system that saps less than a tenth of one horsepower from the engine as it works.
The AWD system ensures that basically all the bike’s power goes to the rear wheel under acceleration, until the wheel loses traction and starts to spin. At that point, a percentage of drive is smoothly transferred to the front wheel, pulling the bike forward and simultaneously allowing the rear wheel to regain traction.
By all accounts, the system works superbly, particularly in really tough terrain. The AWD bikes simply drive up hills and through ditches that have normal Enduros bogging down, fishtailing and falling over sideways, and in situations where riders are forced to nurse the bikes over large and unwieldly obstacles, the front wheel drive system really shines.
An additional benefit of AWD is that the front wheel doesn’t want to wash out under cornering forces. On a normal bike, the front wheel locks up and pushes out under hard turning forces; the instant the front wheel starts to lock up with Christini’s AWD system, power is delivered, forcing it to turn and making it extremely difficult for the front end to slide out.
Though the front wheel drive shafts come down in parallel with the forks, the drive is unaffected by fork compression and rebound due to a linear bearing that extends and retracts the drive shaft without binding, making the Christini the first all-mechanical system that can cope with the long-travel suspension found on modern dirt bikes. There’s no torque reaction to front-wheel acceleration because the drive shafts to each side of the wheel rotate in opposite directions.
The entire system adds only 15 pounds to the weight of the bike – compared with the 19 pounds of the Ohlins system used by the Yamaha and KTM.
The system has already proven effective in hard enduro racing, with its reliability successfully tested in World Enduro, GNCC, Endurocross, Red Bull Last Man Standing and Hare scrambles over the last few months. Christini riders have consistently placed well, raising eyebrows amongst competitors, and are unanimous in their praise for the system. The effect is equally amazing for novice riders, who will simply spend less time stuck or falling over and will suffer noticeably less riding fatigue, the company claims.
At near on US$6000 for a Christini conversion kit, it pretty much doubles the price of your CRF250R or CRF250X (CRF450X models are coming soon and KTM kits are in development). The ordering process is a little frustrating – Christini require you to send in a brand new frame and forks which they’ll exchange for modified ones. If your bike’s not brand new, you can still send it in to be modded, but you’ll have to wait for your individual unit to be worked on. Once you’ve got the frame and forks back, you’ve still got to assemble the rest of the bike before you can go play.
Christini believe their AWD system is under close scrutiny by the major manufacturers, and it’s possible that we’ll see the small company swallowed up and the technology offered standard on bikes straight from the shop. Meanwhile Christini is ramping up production and has started shipping kits to American customers, with a view to a cautious expansion into Europe and other areas in the future.
