Again using a Photoshop image, we measured the frontal area of the '96 RS125, which proved to be 3.40 ft2 (0.316 m2), leading to a CD of 0.644-which doesn't compare that well to the Hayabusa and ZX-12R. In other words, the RS125 has an aerodynamic advantage because of its smaller frontal area, but not because of a particularly streamlined shape. Generally, the GP bike fairings weren't very good because they left too much of the rider's body exposed. Cooper predicted the racebikes would have a large improvement in performance with good fairings.
Next in the tunnel was a half-faired Suzuki Bandit 600, which produced a CDA of 3.94 ft2 (0.366 m2). The Bandit was followed by a fully faired GSX-R750, which produced a CDA of 3.49 ft2 (0.324 m2). With an obviously smaller frontal area than both the Hayabusa and ZX-12R, the GSX-R produced less drag than the ZX-12R, but still more than the Hayabusa, confirming there's more to motorcycle aerodynamics than a small frontal area.
It seems we may have reached the point with streetbikes where horsepower and aerodynamics have produced the maximum velocity authorities are willing to tolerate, but we have by no means reached the limits of what is possible. For all the hype surrounding Kawasaki's ZX-12R, the wind tunnel shows it fails to surpass the bike it was designed to beat for the most elemental of reasons. The Suzuki Hayabusa deserves to keep its title as the world's fastest motorcycle.
Thanks to Kevin Cooper for assistance with this story.
Editor's Note: Since this story first ran in the Sept./Oct. 2000 issue of Cycle Canada, some interesting info has come to light from our Man In Japan, Don Helle. Eight years ago, when Kawasaki engineers were designing the original replacement for the ZX-11, the prototype resulting from wind tunnel testing was almost a carbon copy of the Hayabusa-only the company figured it was too ugly to sell. And a Kawasaki engineer has confirmed the ZX-12R was in fact "neutered" to a lower top speed in its final stages of development. See Late Braking for the complete story.
|BIKE ||CDA (ft2) |
|1990 Honda RS125 ||2.08 |
|1996 Honda RS125 ||2.20 |
|Suzuki Hayabusa ||3.37 |
|Kawasaki ZX-12R ||3.67 |
|Suzuki GSX-R750 ||3.49 |
|Suzuki 600 Bandit ||3.94 |