BMW R 1100GS 75th Anniversary

The BMW GS an ordinary motorcycle? Many would say: no, it's an idea expressed in two-wheeled form. Or, at the very least, a true phenomenon. A trailblazing creation, in fact.

When BMW launched the G/S back in 1980. it was emphatically out there on its own. It signaled the start of a new motorcycling concept: an enduro with a large engine and plenty of power at its disposal to achieve a masterful blend of ride comfort and ruggedness. In fact, it soon became the trendsetter for an entirely new range of machines.

In 1981, only a year after its launch, Hubert Auriol won the Paris-Dakar Rally on a competition version of the BMW R 80 G/S, proving that its high-tech features and the harsh desert environment were an enticingly exotic match. Three more victories in what is probably the toughest rally in the world followed in the course of the 1980s.

The long list of G/S triumphs extends right up to the present day. And it includes a few surprises, such as Jutta Kleinschmidt, winner of the Ladies' Category in the "Paris-Cape Town" adventure rally at the start of 1993 on a near-standard R 100 GS PD.

These victories were not the only reason for the immense public appeal of the GS. It has been voted Enduro of the Year in Germany nearly every year since 1980, and more than 60,000 have been built by 1994.

The horizontally-opposed Boxer engine was the obvious choice for the 1994 GS. Not simply because it reflects the bike's temperament, but above all because of the fundamental advantages that this engine principle offers for a large enduro. In addition to its refinement and pulling power, the Boxer engine has a low center of gravity and excellent heat dissipation from the cylinders in the air stream.

The 1994 BMW Boxer engine, available on the R 1100 RS. confirms that the horizontally-opposed Boxer concept still offers ample scope for development. Riders and members of the trade press gave it rave reviews. For example, the German magazine "Tourenfahrer" wrote in its May 1993 issue: "Even with a 'mere' 90 horsepower, the BMW has nothing to fear from any other superbike".

But we had ambitious plans for our new enduro, since its priorities were by no means the same as for a sports touring bike. High torque, for example, was more important than sheer power. In other words, we needed an engine with smooth, easily-regulated flow of power even at low engine speeds, permitting energetic acceleration at any time.

The 1994 Boxer engine on the BMW R 1100 GS satisfies these requirements and more. Even just above idling speed the large high-performance engine delivers ample torque - over 58 lb-ft from 2,500 rpm up to almost the engine speed limit. Peak torque of 71.54 lb-ft is reached at only 5,250 rpm. The advantages are obvious: impressive traction when it's needed, but without the excessively high engine speeds that cause increased material fatigue.

The maximum power output of 59 kW (80 bhp) at 6,750 rpm means that high continuous speeds are possible on the highway

The 1994 BMW Boxer satisfies the requirements that the enduro engine of the future must fulfill. Thanks to its completely new mechanical layout and engine management by ultramodern Digital Motor Electronics, the new two-cylinder engine can claim greater economy, durability. robustness, ease of repair and, above all, environmental compatibility. A key feature of the Boxer engine is the high-camshaft control with four valves per cylinder, which maximizes engine efficiency and minimizes both exhaust emissions and fuel consumption.

The advanced running gear on the 1994 BMW GS is illustrated most impressively by the BMW Telelever, BMW's new front suspension system that has already demonstrated what progress means on the BMW R 1100 RS. All test riders agree that our objective of creating a superior alternative to the telescopic fork has been achieved.

The Telelever can excel to an even greater degree on the 1994 BMW R 1100 GS than on the R 1100 RS sports tourer, because the concept is really put to the test on poor surfaces.

A glance at its operating principle reveals why this is so. The Telelever combines the advantages of the front fork and front swinging arm. In other words, it still has fork tubes, with the difference that they no longer contain springs and dampers. Instead, a single central spring strut performs their function.

The fork is mounted on a bridge between the sliding tubes on a leading arm, and on a ball joint (ball-jointed fork) at the front of the frame. The ingenious feature of this layout is that steering movement is made possible by the ball joints on the sliding-tube bridge and in the front frame. These ball joints are free from play and require no maintenance. Braking forces are largely introduced into the rigid engine housing by way of the lower ball joint, which is bolted to the leading arm. The leading arm is pivoted to the engine housing. The upper ball joint is bolted to the fork bridge.

In contrast to the telescopic fork, castor angle and wheelbase remain largely unchanged across the entire range of suspension travel even when the suspension is compressed a long way, thus ensuring maximum stability in all riding conditions.

A useful anti-dive effect, which prevents the motorcycle from plunging forward when the brakes are applied forcefully, is also achieved. Consequently, there is always sufficient spring travel available - a vital improvement in comfort and safety on poor roads.

And the fact that there are now no fork support springs means that very little friction is caused, and suspension response is significantly better.

A factor that is particularly important for off-road riding: the entire structure is very strong, but light weight and virtually non-wearing. The fork tube seals scarcely have any loads to bear, and a steering head bearing that would otherwise be subjected to high loads is unnecessary. The typical problems encountered by conventional telescopic forks are avoided - the Telelever can accordingly clock up 62,000 miles without the need for maintenance.

The impressive technical maturity of this solution was confirmed by Motorrad magazine (issue 18/93) which evaluated various alternatives to the BMW R 1100 RS Telelever. Its conclusion: the testing team considered the Telelever to be the most impressive, highly advanced concept of all.

In contrast to the sports touring version, the Telelever for the BMW R 1100 GS has been adjusted to obtain a suspension layout that satisfies roadgoing and off-road conditions equally well. The new front spring strut illustrates this most clearly: with 7.58" of spring travel, it easily absorbs the most extreme surface irregularities; in addition, spring preload can be set to five different rates. allowing the rider of the GS to adopt preferred settings for any given surface conditions. A further innovation: the handlebar is decoupled from the Telelever by a pivot structure, so that the rider does not feel the turning movements that result from the considerable amount of spring travel.

WITH SECOND-GENERATION BMW ABS.

The first ABS for motorcycles was invented by BMW, and has long since proved its value on roadgoing motorcycles; over 40,000 riders of BMW motorcycles to date have chosen this important option. Their decision was a sensible one, because if the brakes are applied forcefully, ABS prevents the wheels from locking; in many circumstances locked wheels would cause the rider to be thrown off the bike.

This added feature is now available for the first time to enduro riders. Experience has shown that large enduros clock up most of their miles in ordinary traffic - and therefore have to cope with increasingly demanding riding conditions. It's good to know that ABS is there for you.

On the other hand, as every professional knows, in order to keep the motorcycle under control in off-road conditions or on loose surfaces, it may be necessary to have one wheel locked for reasons of stability or effective braking. A stationary rear wheel builds up a wedge of loose material between the rear wheel and the ground, to help brake the motorcycle.

The solution chosen for the new BMW R 1100 GS: the new ABS II, available as an optional extra, can be switched off whenever its effect might be undesirable.

In actuality, this will hardly be necessary. The ABS II is so effective that even BMW test riders have difficulty performing better. Test rides show that ABS II performs well on unstable surfaces - it's even been known to stop on ice without locking the wheels.

BMW ABS is, therefore, always activated unless the rider deliberately switches it off. This prevents any unpleasant surprises as a result of it having been shut down inadvertently; the ABS can only be switched off by pressing the cancel button at the same time as the ignition is turned to start the engine. Whenever the ignition is switched off and back on again, ABS is automatically reactivated.

The new ABS II has mature software that is designed to cope with even the most unusual braking conditions. For instance, it takes effect even before a rear wheel leaves the ground as a result of excessively violent braking.

Very advanced technology is used: ABS II for the first time has a "piston system with relative pressure monitoring". This system maintains the braking effect at a very high level throughout the period for which the brakes are applied hard.

Its functional principle: rotation of both wheels is permanently monitored by sensors and the readings passed to the ABS control unit. If this identifies a tendency on the part of one or both wheels to lock. the pressure modulator is activated. It reduces braking pressure until the locked wheel begins to turn again.

The moving piston in the pressure modulator deliberately modifies the volumetric ratios and, ultimately, the brake pressure in the system for this purpose - separately for the front and rear wheels, of course.

This piston's high-speed actuation by means of a piston position monitoring sensor, together with the high-performance control unit, ensure that brake pressure is never reduced by more than the necessary amount.

The system has been developed to respond within four thousandths of a second. The wheels can always be braked just below the locking point without sacrificing any valuable braking distance.