Passing Interest and Passing Ability

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Most of us who are interested in fast cars have at least a passing interest in their two-wheeled counterparts. Even if that interest is confined to when we are stuck in a traffic snarl-up and one of these generously shod, sleek and thunderous machines slithers past, up to the head of the jam, and off into the distance. Then one is generally interested in being on such a bike, and not stuck in a fuggy and overheating four-wheeler. But genuine interest goes beyond this mild form of envy for it is clear that today’s generation of motorcycles are of a technologically advanced breed. They are astonishingly fast, with stupendous brakes and roadholding, and many of the machines one can see on the road do not look all that far removed from the sort of machinery used at the Isle of Man TT races. Of course this has for a long time been the case with motorcycles; much more so than with cars; a production sports car bears very little resemblance to a Sports-Prototype Group C car or Formula One machine. A road-going motorcycle has always been close in its basic conception to a racing machine, the parameters for construction being that much more limited than on four wheels. That might also be the reason for the astonishing development in technology where motorcycles are concerned; a manufacturer who wishes to progress has to wring that much more out of a definitively small engine and a geometrically confined chassis design. Today’s normally aspirated Grand Prix motorcycles with 500cc two-stroke engines develop approximately 175 bhp! That is 350 bhp per litre, whereas today’s F1 cars are still short of 200 bhp per litre.

A comparison of four-stroke engines would have them on a par; Honda’s RC30 750cc racer develops approximately 150 bhp. But this brings us back to the original point that road bikes are not too far removed from racing machines, because one can buy a road legal RC30, take to the local bypass, and give an awful lot of Ferrari and Porsche drivers a considerable surprise. Ducati’s road-going 851 for example, a machine derived from their 888 Superbike contender, has a power to weight ratio of approximately 611 bhp per ton. That of a Ferrari F40 is approximately 440 bhp per ton and a Porsche 911 Carrerra 4 a mere 170 bhp per ton.

It was when our editor was passed by a very fast `kamikazee’ motorcycle, that he decided it would be interesting for there to be the odd column in MOTOR SPORT that would keep the four-wheel enthusiasts in touch with what is going on in the two wheeled world. Long standing readers will remember that DSJ has written on motorcycles in the past (and with much authority too) and very long standing readers will remember that in the twenties MOTOR SPORT was as much a magazine for motorcycles as for motor cars.

I probably run the risk of teaching many old dogs new tricks, and if so I ask you to bear with me. Those of you who are up in the motorcycling world will know that early summer means the ‘TT races on the Isle of Man, and there are few better festivals of motorcycling and racing to demonstrate the technology of today’s machines, the astonishing speeds of which they are capable, and the affinity they have with what one can buy in the local show room. The main difference between the TT today and in days gone by is that it no longer holds Grand Prix status and so one does not see any of the really advanced 500cc V4 two-stroke Grand Prix machines, the Fifties and Sixties equivalent of which would have been the Nortons, MV Agustas and Gileras of Duke, Surtees, Hailwood, and Agostini.

The smallest machines at the TT are not necessarily the slowest. The 125 and 250cc machines are more or less unrestricted, and although they are not actually World Charnpionship Grand Prix motorcycles they are what you might call Grand Prix inspired. They are one and two cylinder two-stroke machines with crankcase reed-valve induction, and pressed one or two piece crankshafts with roller bearings. The chassis are generally twin beam, of aluminium or steel box section, with box section rear swinging arms. Although the box section chassis is not a new idea, having first been used in Ariel, New Imperial and Francis Barnett bikes, it offers greater torsional rigidity and is state of the art in today’s chassis technology. Machines of all capacities use it, except of course for Ducati who in their Latin way stick steadfastly to spaceframe construction, insisting that it is every bit as good. They might well be right; their works racers are certainly showing a clean pair of heels to all other manufacturers in this year’s Superbike World Championship.

The two-stroke engines in the smaller machines clearly illustrate how powerful fully developed racing bikes can be, considering their capacity. The 125s produce 40 bhp, the 250s 80 bhp, and these machines can lap at astonishing speed. This year’s 250 event was won by Ian Lougher on a Yamaha, with a fastest lap of 117.80 mph; only 5 mph short of the absolute lap record!

The production based 400 and 600 Supersport classes are a bit more interesting so far as road bikes are concerned, the machines to be riding this year being race-modified VFR400R Hondas, FZR400 Yamahas, and FZR600 Yamahas. MOTOR CYCLE SPORT’s man Ray Knight took part in the Supersports 400 race on a standard road-going Honda VF400R. With standard Japanese tyres he clocked a race lap at over 100 mph and finished in 20th place. The four-cylinder, water-cooled, twin overhead camshaft 16 valve engine produces 63 bhp and will rev to 15,000 rpm! Ray was clearly very impressed with the machine, saying that the handling was superb and troublefree at speeds of up to 140 mph. Some would be worried, others excited by the fact that such a machine can be bought from one’s local motorcycle dealer.

Dave Leech won the Supersport 400 race with a fastest lap of 109.39 mph, and Reid won the Supersport 600 race, although the fastest lap of 114.21 mph was once again established by Leech. If these lap speeds don’t seem that impressive to you, try to have a look at a map of the Isle of Man, and then reflect that the circuit is 37 miles long with narrow, stone-wall lined roads sweeping up mountains and through village squares. It is indeed a very thorough testing ground of the capabilities of machines and riders, and it is very much a road race; for the rest of the year these country roads are used by ordinary traffic.

The main race of the TT festival is the F1 Senior race that takes place at the end of the week. This year’s race was blighted by rain, but the fastest lap, established by the winner Carl Fogarty, was still at a blistering 116.47 mph. The absolute lap record stands at about 123 mph. The bikes in this race are production based four-stroke machines of up to 750cc, but controversy is still raging as to what category the Norton comes under. It has a Wankel engine, with what is generally (although not absolutely) accepted to be a 588cc engine. It produces 155 bhp, and has a top speed of close to 190 mph. Trevor Nation rode his Norton to second place this year behind the winning machine, a 750 Honda RC30. This is the big brother of the VFR 400R that Ray Knight rode, but obviously a fully race-modified machine. It is also a V4 with twin overhead camshafts, and four valves per cylinder, and it produces approximately 150 bhp. Chassis technology in these machines remains essentially the same as with the smaller capacity motorcycles with twin beam aluminium box section frames using the engine as a stressed member. Rear suspension is with a single shock absorber that is adjustable for pre-load, compression and rebound, and many of the bikes feature upside-down front-forks, the advantages of which are greater rigidity under braking, and less unsprung weight. Another relatively recent innovation is rising rate suspension where the geometry of the suspension, and position of the single shock absorber is so calculated that suspension resistance increases as wheel deflection increases.

The exciting thing about this racing motorcycle technology is that it is directly relevant to the machinery one can buy on the road. Today’s top road bikes are a few modifications away from machines that can put in a competitive lap time at the Isle of Man, and as Ray Knight demonstrated, a completely standard bike can still be only a few mph off the winning pace. They are genuinely race-bred machines when it is quite doubtful, and certainly less obvious that Sports-Prototypes and Formula One machines have anything like as much bearing on even the fastest of today’s road-going sports cars.

On a highly tuned road-legal motorcycle, the chassis, suspension, brakes, engine and tyres are all born of the cutting edge of motorcycle technology: the racing machine. CSR-W

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