BMW R1100S
High-compression pistons and improved breathing helped make the I085cc engine BMW's most powerful boxer motor ever. Cylinder head covers were magnesium to save weight.
Swoopy styling, low handlebars, bright yellow paintwork, a high-level exhaust system with underseat silencers, and a single- sided swingarm all combined to give the R1100S a truly sporty look.
The stylish and rapid Rl 100S arrived in 1998 to prove that BMW's traditional flat- twin format was still very viable for high- performance motorcycling. This was the most aggressive roadgoing boxer that BMW had ever built. The German firm referred to it as a ‘sports- tourer with the emphasis on sport*, and the l lOOS was quick, agile and well-braked enough to hold its own in serious company.
With its two sticking-out cylinder heads, there was no mistaking that this bike was a BMW. But the S had a very distinct style of its own. notably at the front end with its big ellipsoidal headlamp lens. The asymmetrical theme was echoed in the fuel cap and instruments; further back, the rear end was notably lean and sporty.
The new bike’s I085cc air-cooled engine, based on the eight-valve, high-cam unit from the touring- oriented Rl 100RS. made this BMW's most powerful flat twin yet. It was tuned with new pistons that gave increased compression ratio.
Breathing was also improved by a new air filter design, plus a revised Motronic engine- management system.
A new exhaust system, complete with twin silencers in the tailpiece, also helped increase peak output by 8bhp to 98bhp at 7500rpm. Forged conrods helped keep the engine together at its higher 8500rpm rev limit, and crankcase oil circulation was improved. Although it retained shaft final drive, the 1100S also had a new six- speed gearbox.
Much of BMW’s effort in the Rl lOOS's chassis design went in ensuring that this was not just the best-handling boxer yet, but also reasonably light. At 461 lb (209kg) dry it was still heavier than its closest rivals - but not by much. Some of the weight-saving came from a new and lighter \er4on of BMW’s Telelever monoshock front suspension system, which featured a remote rebound damping adjustment knob in the steering head area.
Aluminium main frame
As with other four-valve boxers, the engine and gearbox housing were also stressed members of the chassis, but the 1100S differed in having an aluminium main frame. A tubular steel rear subframe supported the Paralever rear suspension system, which gave a clean and racy look from the left. Wheels were new. lighter l"-inchers wearing sticky radial rubber.
The mildly tuned boxer engine pulled well from low down, and revved w ith more enthusiasm than previous boxers. The S was ver> happy to sit at an indicated 85mph (137kmhi. just under 5000rpm in top gear, feeling smooth, stable and unstressed. Above that figure the engine felt a bit harsh, but the BMW had plenty of acceleration in hand to a top speed of 140mph (225km/h).
It was the new bike's chassis that made the biggest impression, because this Rl 100S handled like no other BMW roadster. Its chassis geometry was close to the race-replica norm, and the bike impressed with the ease and precision with which it went round corners given a light flick of the sportily low-set handlebars.
The Telelever front end gave a great combination of quick steering and stability. particularly when braking hard into a turn. Suspension at both ends delivered plenty of feedback, and was well-damped enough that the bike remained composed even when accelerating hard out of bumpy bends. The front-brake combination of four-piston Brembo calipers and 305mm discs was excellent, too.
The R1100S was a bike that stood out not for traditional BMW attributes such as long-distance comfort or refinement, but for light steering, powerful brakes and a liking for speed. It was an enjoyably fast, fine-handling machine that put BMW firmly in the sports bike market for the first time since the R90S of the mid-1970s.
Handling was excellent, with a light and neutral steering feel, reasonably firm and well-damped suspension, and Not everyone liked the asymmetrical headlight design, but this was one BMW that nobody could accuse of looking ordinal
Specification BMW R1100S (1998)
- Engine Air-cooled high cam eight-valve flat twin
- Capacity 1085cc (99 x 70.5mm)
- Maximum power 98bhp @ 7500rpm
- Transmission Six-speed, shaft final drive
- Frame Cast aluminium and tubular steel
- Suspension Telelever monoshock front; monoshock ^ea'
- Brakes Twin discs front; single disc rear
- Weight 4611b (209kg)
- Top speed 140mph (225km/h)
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