Chassis

Besides high power and light weight, perhaps the most fundamental factor affecting the design and optimum performance of any sports-oriented motorcycle is the way its weight is distributed. Since motorcycles, unlike cars, bank and turn around two axes-an 'earthbound' variation of the roll and yaw characteristics one associates with aeroplanes-any excessive weight or mass positioned near the machine's outer extremities exerts a strong inertial influence on-and resistance to-its ability to swiftly lean and change direction. Thus, nearly all recent racing machines and many high-performance Supersport motorcycles have come to be designed with a growing emphasis on the concept of mass centralisation.

Every part-from lighter wheels and suspension components to such seemingly trivial details as the substitution of plastic for glass in a headlight's construction-has a significant effect on a motorcycle's ability to respond to its rider's inputs with smooth and quick directional changes, and this influence grows as speeds increase. Extensive efforts made to move heavier components-including the rider-closer to the motorcycle's rolling centre of mass, and to lighten those components positioned furthest from the central radial axes result in quicker, surer, more responsive handling while emphasising the rider's feeling of close integration with the motorcycle.

Like the RC211V from which it receives its primary design influence, the totally new CBR600RR features a more compact form designed primarily for racetrack dominance. Its uniquely constructed new frame, innovative chassis layout and advanced, MotoGP-class suspension system combine to provide an unprecedented level of performance and almost paranormal response that will soon be shedding seconds off lap times from Suzuka to Silverstone.

New, RC211V-Based Frame Design

Specifically designed to achieve smaller dimensions and more centralised mass, the CBR600RR's frame positions the rider closer to the steering head and almost directly above the machine's centre of mass, a position made possible by a total rethinking and redesign of the CBR's fuel tank. While overall frame rigidity is comparable to the current CBR600F and F/Sport, lateral rigidity around the steering head was increased to better stand up to the stresses put upon it by the front suspension as the bike flicks from side to side.

While high rigidity is certainly an important aspect of frame design, too much rigidity in the overall frame can sometimes result in a rough ride and imprecise cornering control, especially over uneven road and track surfaces. With this in mind, the RR's torsional rigidity was reduced slightly near the centre of its frame to lighten and ease handling in quick manoeuvres, and enhance wheel tracking to help the machine better settle into its line through the corners.

The end result of these modifications and improvements is the quickest and surest side-to-side cornering and smoothest handling ever experienced in a street-going road bike-and the most dynamic mix of lightning response and near-transcendental cornering control ever achieved in a circuit-scraping race bike of any class or displacement.

The secret to this remarkable handling prowess lies in its revolutionary frame construction.

Innovative Welded Hollow Die-Cast Frame

Modern leading-edge chassis production for the highest performance Superbike and Supersport motorcycles on the market has for quite a few years now been based on a precisely configured combination of aluminium extrusions, castings, pressings or forgings welded together in the frame's construction. The CBR600F, among other leading Supersports in the Honda stable of race-ready streetbikes, has also been a prime recipient of this leading technology.

Now, in a quantum leap that represents the culmination of years of research into metallurgy and frame production technologies, Honda introduces a revolutionary new development in aluminium casting technology for frame production. Completely unlike the extruded aluminium main spars of Honda's leading Supersport machines till now, the new CBR600RR features freely formed, hollow-section unit die-cast aluminium frame sections welded between its die-cast aluminium steering head and pivot plates.

While the world's first application of open channel Fine Die-Cast technology can be seen in the production of the current CBR600F and F/Sport's pivot plate frame sections, the new CBR600RR takes this technology another quantum leap into the future with the first successful mass production application of leading-edge Hollow Fine Die-Cast technology. Used in the production of the main structural components of a motorcycle, this revolutionary advance not only realises the ideals of strong, lightweight construction, but also opens the door to new worlds of creative freedom with more organic structural shapes that can take full advantage of aluminium's light weight, strength and structural flexibility.

The process is based on conventional injection sand casting techniques, which are more often used in the production of solid objects in an infinite array of shapes and sizes. Casting larger, more complicated shapes, like frame sections has always been possible, but never before in such thin-walled hollow configurations, owing to the crumbling of the sand-formed interior mould sections ('sunanakago' in Japanese casting industry terminology) as the molten aluminium is injected into the mould.

In a new development in the die-casting process, Honda succeeded in coating these sunanakago in ceramic, which helps them retain their shapes even when exposed to the high temperatures and pressure of the aluminium injection process. Then, after the aluminium cools and hardens, these internal casting sections can be easily broken up and removed from the hollow interiors of the frame sections, leaving only a smoothly dimpled finish and achieving an unprecedented thin wall thickness of only 2.5mm-where before the thinnest possible cast wall thickness had been 3.5mm-which makes a significant contribution to the frame's lighter weight, not to mention its unique configuration.

The new CBR600RR's revolutionary new hollow die-cast aluminium frame is constructed of nine pieces (1 steering head, 2 engine hangers, 2 pivot plates, and 4 interconnecting sections) all welded together to form one solid, organic whole. Die-cast aluminium has, until very recently, been extremely problematic to weld, since any foaming or other imperfections in the molten aluminium during the high-speed, high-pressure injection process can trap moisture and air bubbles in what are known in the industry as 'blow holes.' When later exposed to the instantaneously high temperatures of welding, these blow holes furiously sputter and pop, resulting in flawed welds, ugly surface imperfections and possibly impaired structural strength.

Honda solved this potential problem through the development of its new sunanakago Fine Die-Cast technology and the precise control of both the temperature of the molten aluminium and the speed of the injection flow, which was slowed just enough to ensure flawless castings with no imperfections that might adversely affect weld strength.

New Die-Cast Aluminium Seat Rails

The CBR600RR's frame is not the only component to see the results of Honda's new Fine Die-Cast construction. Remarkably, even its seat rails received this treatment in order to create a simply constructed yet lightweight and structurally strong, organically designed mount for both rider and rear tail cowl assembly that perfectly surrounds the CBR's large, new, centrally positioned exhaust system while providing optimum strength and rigidity.

A conventional welded steel or aluminium seat rail, constructed primarily for lightness and strength, would require that the CBR's underseat exhaust system be bent to fit its narrow design parameters, and as a result would likely have an adverse affect on engine performance.

Instead, the CBR's new casting process allows the seat rails to be formed to a custom fit around the silencer's optimum positioning and trapezoidal shape while at the same time greatly reducing manufacturing time and costs by only requiring five pieces in its construction: the two rails mounted to the frame and three bolted-in cross-members that provide assured lateral strength and rigidity. The two rails themselves curve inward to bolt together at the rear, providing added structural strength without the need for expensive, time-consuming welds. This modular design also facilitates maintenance while reducing weight.

New Centrally Positioned Fuel Tank

Perhaps the most impressive change in the new CBR600RR's layout, albeit the least visible, is the complete redesign and repositioning of its fuel tank.

One of the major challenges (and frustrations) for high-performance motorcycle designers has always been to find the ideal position to carry a full tank of fuel on a motorcycle-and have it still look like a motorcycle. The traditional location over the engine-although often one of the most attractive points of focus in a motorcycle's design-invariably concentrates a large lump of shifting/sloshing inertial weight at the highest point in the bike's form. And with a full charge of 18 litres weighing in at approximately 710 grams per litre, that adds up to a hefty sum of nearly 13kg that the laws of physics decree will be resistant to any rapid side-to-side changes of direction. This high-positioned load of mass and weight represents one reason road racers find the last laps of a race much quicker and easier-handling than the first laps, owing to the unsettling way that this large can of fuel affects handling and slows cornering response.

Under the new CBR600RR's sleekly designed and conventionally proportioned fuel tank cover resides an entirely new idea in weight and mass apportionment. The forward half of the space under this cover is taken up by the induction system's large 6-litre aircleaner assembly, with its Dual Sequential Fuel Injector system installed within. The rear half-closest to both the rider and the motorcycle's centre of mass-is taken up by the fuel tank, exactly like the revolutionary new RC211V. However, only the upper third of the pressed steel fuel tank is visible over the upper rails of the frame. Below that, reaching far down to the upper surface of the engine's crankcase, lies the major bulk of the new CBR600RR's fuel capacity, carried as close as possible to this race-ready machine's centremost turning axes.

The impressive result of this fundamental change in design is two-fold. First, the change in fuel tank shape permits the rider's seating position to be moved a full 70mm forward relative to the steering head, resulting in a smaller form with its mass more effectively centralised around its rolling axes. Next, the centralised positioning of the fuel's weight results in a lighter and more responsive handling feel that enhances quick changes in direction while remaining essentially neutral, regardless of how much fuel it is carrying.