Development of the BMW R 1100 S.

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Development of the BMW R 1100 S.

Development of the BMW R 1100 S.
Sports community

Not only the fans have waited long enough for a sports boxer. A number of BMW engineers also welcomed this order vehemently.

Fred Siemer


Some of the secrets of BMW motorcycle construction are only revealed by chance. For example, during a short trip with Munich technicians and the new R 1100 S, MOTORRAD found out that the development department was dominated by men who were enthusiastic about younger BMW specifics out of sheer self-interest. The gentlemen are turning on the gas very boldly. Tele and Paralever are just right, ABS anyway. And performance can never hurt.
Markus Poschner, Head of Design for the Complete Vehicle, admits that he realized his dream BMW with the S. During the brainstorming for this project, he and his like-minded people trusted those BMW customers who still rave about the S-models of the old two-valve boxer. Almost athletes with all-round appeal, next to which an R 1100 RS almost looks chubby. In 199 (5) the marketing also recognized opportunities for this type of device, the trim regimen could begin. Taking into account the current and expected noise and exhaust gas values, the four-valve boxer should be brought to its peak of performance and the weight should be frozen at 230 kilograms. Even these tops of the specifications show that the BMW faction, which almost fundamentalistically demands everything from a motorcycle, could once again be overruled. The cruiser introduced last year is also targeting a niche with high sales potential. With the S, so development chief Wolfgang Durrheimer indicated, is now over: “Six boxer rows – the RS will be continued – are enough.”
Sportier than the RS, but not a super sports car. A squat seating position, direct feedback from the front wheel, spontaneous handling: VFR and then also VTR from Honda were always in the sights of the developers. Fortunately for BMW, both are around 100 hp, so the aforementioned performance peak is sufficient. “More than 98 hp cannot be extracted with a reasonable amount of effort,” explains the Boxer series manager, Benno Brandlhuber. “We already had to make a lot of effort on the inlet and outlet side.”
This includes, for example, a flexible hose that guides the air from the Ram Air mouth of the fairing to the throttle valves. It was designed in such a way that no resonance vibrations arise and is of course easy to lay. Incidentally, the technicians favored Ram Air because of the cooler combustion air, not because of the dynamic pressure, which is almost irrelevant in terms of performance. A Bosch Motronic MA 2.4 adopted from the K 1200 RS, but modeled on the boxer, controls the mixture composition, the valve train remained untouched except for the thinner valve stems.
Because the engine had already been tackled, its ventilation was also renovated – previously problematic due to the lively pulsations of the boxer and now solved for all types. Also new for all BMW twins: the pump draws in the oil through double suction guides. From this, as well as from the oil cooler, which is larger than the RS, it may be concluded that the operation performance center also led to the thermal limits of the air / oil-cooled boxer.
Of course, all these measures pale against the effort and pain that came with the weight regimen. In detail: The exhaust weighs only twelve kilograms despite the additional interference pipe between the manifolds. Magnesium cylinder head covers save 800 grams, while the Telelever cut off 1.5 kilos. The aluminum tank has to be modest with a volume of 18 liters, the coupling is controlled via a very thin line. The carbon fiber fender brings a few grams over the front wheel, a total of two kilos a smaller battery and a less powerful alternator.
But just then a vicious circle began: ABS needs electricity, and not too little. This is precisely why the extra weight in this extremely popular and recommendable BMW option is higher than usual this time. If you want ABS, you also get a big battery and a powerful Lima. If you want an ergonomics package, this time you get – nothing at all. Adjustable notches and handlebar halves weigh too much, so there is only a choice between handlebars mounted under or above the fork bridge.
Like a red thread, the gram-foxing runs through the creation of the S. Gateway, internally BMW calls those approval rounds, in which at the end of each development phase it is checked whether all goals are still in sight. And only at one of these gateways were the R 1100 S. missed her front fender as well as economy lima plus battery.
It was clear from the start, however, that this near-athlete should use the six-speed gearbox of the K 1200 RS. Which logically resulted in a changed frame (see MOTORRAD 15/1998), because unlike the five-speed box, the former cannot take over the swing arm mounting. While the rear boom and the front section of the RS are linked directly to the engine, a light metal construction now arches over the engine, which only has a supporting function. Of course, this frame brings more weight, on the other hand, the new switch box weighs significantly less than the old one. So there was a tie.
The start of series production started on May 5th – with additional processing stations in Berlin, because the boxer series is already booming. This was preceded by a detailed test, at the end of which three motorcycles from the series had to complete 100,000 kilometers. No special occurrences. The developers had almost got used to this, because they also received all-round positive feedback in the so-called field tests, in which pilots selected by customer service gain experience. Even on the racetrack, her test subject, who concentrated 55 percent of his weight on the forehand, could definitely please. Everything is easy?
At the very end, Benno Brandlhuber chats from the sewing box: The heat radiation of the Ducati-style tailpipes had been underestimated for a long time, but remedial action has now been found, which would have been too embarrassing.

Design as a challenge – the BMW boxer in sports gear

Design as a challenge: the BMW boxer in sportswear

Even with the predecessor of the R 1100 S, David Robb and his design team had their fingers in the game: The new boxer started his first with the highly acclaimed athlete study that decorated BMW’s IFMA stand in 1994 (see MOTORRAD 23/1994) sporty tightrope walk. At the same time, it encouraged marketing people and technicians to think even more intensively about a nifty two-cylinder. The former discovered considerable potential and are now even hoping for 30 percent buyers of other brands. The latter marked key data that actually opened up a hitherto unfamiliar field of activity for Robb: Apart from Schorsch Meier’s TT racer, BMW was probably not yet as sporty, which inevitably led to a design line with which the entire motorcycle scene could and should be addressed which also serves as a figurehead for BMW. “BMW from every perspective,” Rob explains, “grown up, but significantly more athletic than the RS.” In order to achieve the basic stance that is almost crouched and ready to jump, the designers shifted the visual focus far forward. Heightened it by the fact that the rear panel is quite massive. “In this way, we were able to achieve amazingly good weather protection at the same time,” emphasizes Robb. In the rear of the S, on the other hand, there is infinite lightness: Seldom has a BMW allowed such open views. Even the slot in the cover of the pillion seat is deliberately placed “because we didn’t want a massive hump impression.” Incidentally, a rucksack can be hidden under the little plastic cover, the shape and color of which is nicely matched to the bike. Of course, the driver will also be able to dress up as a walking S accessory – matching helmets and station wagons are already in the works. There is a horizontal separation between the technology below and the body above. A motorcycle of opposites. And one that is intended to signal technical competence and value from front to back, from the adjustment knob for the front damping to the passenger grab handles. “They should look like a technical detail,” says David Robb, “and not like a purely functional attachment kit.

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