The first-generation CBR900RR was an epoch-making motorcycle that changed the world of super sport bikes forever. It was a model whose development team designed it to offer a precise balance of “defense” and “offense,” judging every aspect of the bike solely on one criterion: whether or not it was the best option for adding to the joy felt by the rider in handling the machine.
One example of “defense” was the front fork, which the development team referred to as “double upside-down,” since its structure was in essence the inversion of an inverted fork. Inverted front forks, which can enhance the rigidity of the front suspension, already had a record of success on racing motorcycles when the CBR900RR debuted in 1992 and were being used more and more in commercial motorcycles. Inverted front forks were no longer very unusual technology, but why did the development team decided to invert an inverted fork for their new model? Their reason was that, although an inverted fork has the merit of contributing greatly to rigidity, they still felt it was not yet ready as a technology for the wide range of road conditions a rider was likely to encounter, since the bike would be used mainly on the street, not the circuit. In order to combine the smooth operation of a regular fork with the higher rigidity of an inverted fork, the team selected a 45 mm diameter front fork that was nearly as large as the outer tube of an inverted fork.
The team selected a 16-inch wheel that complemented this front suspension and preserved the light handling offered by the dimensions of the 750cc advance research stage model. In addition, this wheel helped support the extra load on the front suspension, which the extra power of the higher-output engine could potentially destabilize, and it also offered additional cushioning when the rider touched down after popping a wheelie.
In an example of “offense,” Honda worked with a tire manufacturer to maintain the outer diameter of the tire while increasing its sidewall height. In the early 1990s in Europe and North America, the suspensions of Japanese bikes did not have a particularly good reputation, and the image of the factory front forks and tires as being “on there for now” was difficult to shake. Approaching the suspension design with passion, however, the development team carefully selected not only the best front fork for the CBR900RR but also the best front and rear tires. The team felt confident that Bridgestone was the right choice for the job. At the time, however, Bridgestone’s replacement tire sales network in Europe was not as developed as it is today, so the company strengthened its sales and distribution function there to keep pace with the development and launch of the CBR900RR.
To increase displacement while maintaining the dimensions of the advance research stage model, the development team selected a highly curved twin spar frame. The cooperation of a parts manufacturer was essential to the realization of this part as well. When the team was slowly crafting one prototype at a time, it was able to establish the right curvature, but significant difficulties arose when the time came for commercial production, which for a time seemed in danger of not going forward. An associate in production, however, searched far and wide and secured the cooperation of a manufacturer that could process the frames to create the right amount of curvature, and Honda and the company worked together to realize a high-quality production process.
Thanks to the passionate efforts of Honda associates and suppliers, Honda was able to present to the world the CBR900RR, a completely new concept of super sport bike and, at the time, a motorcycle that was truly unique and without equal.
To take the joy of control to the next level, the 2000 CBR900RR (CBR929RR) featured not only a higher-powered engine but also a much more advanced frame. Instead, however, of depending on the theory of the past, which emphasized maximizing rigidity, the new frame would take the completely new approach of accommodating the model’s higher-powered engine without relying on increased rigidity alone.
Increasing frame rigidity would in fact make the body able to receive the massive drive power of the engine in a stable manner. On the other hand, doing so would also make the behavior of the bike more sensitive to shock, and the weight of the frame would also increase. In other words, increasing rigidity would cause several issues that would have a negative effect on sporty street riding. For this reason, the development team ended up selecting the pivotless frame that had debuted in 1996 on the VTR1000F. Since the swingarm was attached to the rear of the crankcase instead of the main frame, vibration and shock from the rear tire and the drivetrain were absorbed by the greater mass of the engine instead of the main frame. The structure thus allowed the engine to perform part of the work of the frame. The combination of pivotless structure and optimized rigidity throughout the frame made possible the accommodation of higher engine power without the need for increased frame weight.
Helping the engine fulfill its new role as part of the frame were engine hangers positioned near the cylinder heads and a swingarm pivot attached to the rear of the crankcase. On the surface, implementing these changes did not present any technological difficulties. Yet, despite the image of an engine as a rigid body that cannot be bent or twisted, connecting the frame to the area near the cylinder heads would result in the transmission of shock, the effect of which could not be ignored. The concern was that deformation of the engine block, however slight, could increase friction, cause the head gasket to leak or otherwise have a negative effect on performance and durability. By carefully reviewing the dimensions of the pistons and other engine parts, however, the team resolved these potential issues. Having the engine function as part of the frame allowed for a combination of high power and lightweight design, which in turn made possible the light riding feel that is so important on the street.
By implementing the pivotless frame structure and thoroughly refining every area of the vehicle, the team was able to design a 2000 model that was 10 kg lighter than the 1998 model. Moreover, the 2002 model offered 25cc more displacement than the 2000 model yet was a full 2 kg lighter. Yet the development team was not able to reduce vehicle weight by this amount simply by drafting new drawings. Rather, help from parts manufacturers and Honda’s Hamamatsu Factory were also essential. For example, making changes to the order in which welds were made or parts were assembled could have a subtle but cumulative effect on the weight of the finished vehicle. Although numerically small, such reductions in weight could further enhance super sport bike performance and the joy of control. By demonstrating its dedication to this vision, the development team secured the full cooperation of the Honda factory and parts manufacturers, and through a strong collective effort, they were able to shave more weight from the vehicle as if wringing a few last drops from an already dry cloth.
Designing the 2000 CBR900RR (CBR929RR) to accommodate higher power while offering enhanced ease of handling on the street involved overcoming a wide variety of challenges. Achieving the final result required the creativity not only of those designing the body but also everyone involved in the development and production of the model.
If a Formula One race car represents the pinnacle of automobile design, then a MotoGP machine plays a similar role for motorcycles. Between the two, however, is a significant difference. Although a Formula One without a doubt deserves its status as pinnacle of engineering, the technique required to operate it and the dynamic characteristics it exhibits are completely different from their counterparts in an ordinary passenger car. In contrast, a MotoGP machine can be thought of as a commercially produced motorcycle taken to a much higher level. In designing the seventh-generation CBR1000RR to be equally at home on the street and the racing circuit, the development team took inspiration from Honda’s RC211V MotoGP racing machine, which had proven the performance of its body structure in the world’s most prestigious motorcycle racing series.
The team continued to use the twin tube frame that was a tradition in the CBR series, albeit not a revolutionary technology. In designing the frame, however, the team sought to recreate the optimal flexibility found in a MotoGP machine. Such flexibility allowed the frame to support a heavy engine while absorbing shock and vibration from the road. Since even the most advanced computers were not capable of calculating what was required, the team produced prototypes and tested them on the circuit. Adding and subtracting one part after another, the team often ended up with a frame that bore no apparent relation to what they had originally created, and yet again they would return to the R&D Center and create anew. Through this slow but steady process of trial and error, the team succeeded in designing a body that offered not only ample rigidity to accommodate the higher power required for racing but also nimble handling to make street riding more enjoyable.
The new Unit Pro-Link rear suspension was also derived from the RC211V. It was designed to transmit tire movements and other vibrations indicating road conditions in only the amount needed to offer the driver light and nimble control and riding. At the same time the front and rear suspensions would absorb shock from the road and other unhelpful “noise” instead of transmitting it to the frame, thereby helping any rider experience more accurate control of the motorcycle.
First implemented on the seventh-generation CBR1000RR, the Honda Electronic Steering Damper (HESD) was also designed to reduce shock and vibration from the road, thereby preventing undesirably vehicle behaviors and supporting nimble control and stable handling and riding in a wide variety of environments. Offering precise electronic control that responded to vehicle speed, the operation of the system was virtually undetectable to riders, thereby preserving the bike’s light handling feel at low speeds.
In this way, the team’s process for designing the body of the seventh-generation CBR1000RR exemplified Honda’s view of motor sports as a “laboratory on wheels” for testing and refining vehicle technologies.