When I looked at the new Kawasaki ZX-10R, I realized how much accumulated change in rider position there has been in recent years. Both rider and engine have had to be positioned ever-farther forward so that engine power—rising with every new model—drives the machine forward rather than just causing a big wheelie.
In the specific case of the 2011 ZX-10R, Team Cycle World Attack Performance crew chief Richard Stanboli reckons that the engine’s crankshaft is approximately 20mm forward of where it was in the Suzuki GSX-R1000 that Team CW operated last season.
Let’s look at side views: Bikes from the 1950s and ’60s placed the rider’s seatback directly above the rear axle or even a little behind it. The rider stretched forward over a long “breadloaf” gas tank to grasp the handlebars. With the 28-31-degree steering-head angles of those days, the slope of the fork legs placed the rider’s hands inches behind where they are today, when head angles are much steeper at 23-24 degrees.
Today’s “gas tanks” are much shorter and fatter to allow the rider to come forward—no more long breadloaf! In the 1960s and ’70s, the windscreen sloped up from just above the fairing nose and curved to become nearly flat at its rear edge, which was set level with the rider’s shoulders. The screen itself was quite long.
On the 10R, however, almost nothing is left but a little aero screen set at quite a steep angle. With the rider now so far forward, there’s no room for yesteryear’s long, curving screen. Rider Eric Bostrom said he didn’t feel wind pressure on his legs, indicating that they are probably in separated airflow, but felt it quite strongly on his shoulders. So he should, for there is no longer room for a big screen to shield the rider’s shoulders.
In fact, the entire fairing is now 4 inches forward of where it was through the 1970s and into the ’80s. The original fairing rule of 1958 prohibited any part of the fairing from projecting forward of a vertical plane through the front axle. But as engineers have needed to move the rider forward as horsepower increased, the manufacturers have exerted pressure on the rules. First, they allowed fairings to come 50mm ahead of the vertical plane through the front axle and then 100mm (4 inches).
Sealed-intake airboxes on engines with steep intake-port downdraft have to be located right where the gas tank used to be. At first, “helmet-style” gas tanks were made, which surrounded the airbox with a layer of gasoline. Because this pushed weight up high, it interfered with rapid roll maneuvers in GP racing. Designers then started to make “Z-shaped” gas tanks, which placed some gas just behind the airbox and the rest in a “foot” that began to project downward and rearward under the front of the rider’s seat. I first saw such tanks on MotoGP bikes in 2003. On this new ZX-10R, the gas tank “foot” is about 7 inches long, and because it takes up volume formerly occupied by a vertically mounted rear suspension unit, a new linkage has been designed that lays the unit almost flat.
With some of the fuel weight moving rearward in this way, there is even more need to compensate by moving other components forward. One of them is the engine, and this movement fits well with another recent design goal: use of the longest-possible swingarm. The longer the arm, the smaller the angle through which it swings as the rear wheel moves through its suspension travel of about 120mm. The smaller the angle, the easier it is to assure that the rear will not squat during hard off-corner acceleration and push the front.
Now that all the makers have been building this compact, weight-forward style of machine for several years, they have all become very good at packing all the necessary parts into a configuration that allows rider position to continue its move forward. In the process, the packaging has allowed today’s one-liter powerwagons to shrink to a size much closer to that of 600s.