BMW R1200GS

Overall it's intended to be significantly lighter and more powerful than its predecessors and perhaps more use-friendly to ride.

We've had a trawl through the factory information kit and bring you some of the highlights.

Main points

* Reduction in weight by 30 kg (66 lb) ensured by precise calculation, intelligent lightweight construction, and the use of high-strength materials.

* New 1200cc flat-twin power unit with balance shaft for supreme smoothness.

* Power and torque up by almost 18 per cent (100bhp @ 7000rpm with 115Nm torque @ 5500rpm).

* Fuel consumption down by 8 per cent.

* Highly advanced, newly developed engine electronics and the latest emission technology for optimum environmental compatibility.

* Quiet exhaust system with a throaty sound.

* All-new six-speed gearbox with superior running smoothness and shift comfort.

* Newly developed lightweight Paralever with weight-optimised driveshaft.

* New Telelever for even greater precision in front wheel guidance plus low weight.

* Extra stiff running gear for supreme riding safety, outstanding directional stability up to top speed, superior handling and unprecedented accuracy in bends.

* High-performance EVO brakes with on-demand Integral ABS.

* High-strength cast light-alloy wheels and cross-spoke wheels available as an option.

* Electronics used to ensure sensible function with fewer cables and lower weight.

* Electronic immobiliser fitted as standard.

* Wide range of equipment and tailor-made accessories to BMW's high standard.

In detail...

Crankshaft and engine block

The most important innovation featured on the basic engine block is the balance shaft eliminating any unpleasant vibrations: Despite their superior design principle with the cylinders opposing each other to provide a perfect balance of free mass forces (connecting rods and pistons moving to and fro) in their overall effect, conventional flat-twin engines cannot run entirely without vibrations.

The inevitable displacement of the cylinders always generates "circulating" mass forces (that is forces not acting on one and the same level) causing unpleasant vibration the rider will feel on the handlebar, footrests and seat. The severity of such mass forces and the vibrations caused in this way increases as a function of engine size and, in particular, engine speed.

Precisely this is why the engine of the R 1200 GS is the first power unit in the history of the Boxer engine to feature a balance shaft: Running in the opposite direction, the shaft carries two balance weights 180° apart from one another and exactly spaced out in size to provide a counter-force which, superimposed on the mass forces in the crankshaft, reduces vibrations to an absolute minimum. This keeps running conditions smooth and comfortable throughout the entire speed range, vibrations even being dampened in particular at low engine speeds without the flat-twin losing its bullish character.

As before, the flywheel holds the single-plate dry clutch enlarged in diameter from 165 to 180 millimetres (6.50-7.09´´). The clutch lining is free of asbestos and heavy metals, the pressure plate, membrane spring and gear plate being balanced individually to allow easy and convenient assembly of these components without any negative effects on running smoothness.

The structure of the pistons has been only slightly modified versus the previous engine, the new power unit featuring lightweight box-type pistons with three rings which, weighing just 410 grams, are once again a bit lighter still than the former pistons (420 grams).

The crankcase is a lot lighter than before, use of the most advanced computer methods together with innovative casting technology serving to optimise wall thickness as well as the stiffness and strength of the crankcase, weight being reduced in the process by 1.4 kg.

Modified cylinder heads

Maintaining their basic design and configuration, the cylinder heads have also been modified. From outside they are recognisable by their different contours with striking cornered valve covers.

The principle of chain-driven camshafts below the valve plane and the operation of valves by means of tappets and rocker arms has been maintained. The reason, quite simply, is that this design concept has proven its qualities countless times - and although it is not necessarily designed and laid out for high speeds, the concept has confirmed its qualities and reliable function even under tough racing conditions in the BMW Motorrad BoxerCup.

The big advantages of arranging the camshafts in this way are the economic use of space available (width of the cylinder head) and the ease of maintenance so important both in everyday use and on long journeys (adjustment of valve clearance).

Valve diameter is up by 2 mm or 0.79´´ (intake 36.35 mm/1.43´´ versus the former 34 mm/1.34´´, outlet 31 mm/1.22´´ versus 29 mm/1.14´´).

To ensure better and more efficient dissipation of heat, the outlet valves are filled with sodium. Valve duct design has been modified to match the larger valve diameters and the duct contours have been improved in their dynamic flow conditions. In conjunction with the increase in engine capacity, these modifications contribute to the 18 per cent increase in engine output (74 kW/101 bhp) and torque (115 Nm/85 lb-ft). As the final result of this design improvement using the most advanced, computer-aided methods, weight of the cylinder heads has been reduced by 15 per cent.

New engine management

The Digital Motor Electronics code-named BMS-K (BMW Engine Management System) is an in-house development tailored specifically to the requirements of a motorcycle. Fully sequential fuel injection, integrated knock control, faster processing of complex sensor signals by means of the most advanced microelectronics, compact layout and low weight are the most important features worth mentioning in this context. The principle of indirect air volume monitoring and control by means of the throttle butterfly angle and engine speed (alpha-n control) carried over from BMW's existing motorcycles has been further enhanced on the R 1200 GS, creating a concept referred to as torque-based engine management.

The basic parameters determining the optimum engine operation point remain engine speed and the throttle butterfly angle monitored by a separate potentiometer on each cylinder. Applying additional engine and ambient parameters (such as engine temperature, air temperature, and air pressure), engine management, together with control maps and correction functions contained within the system, tailors the injection volume and ignition timing exactly to the engine's and rider's current requirements. Taking so many factors into account, the system is able to control torque with supreme accuracy, adjusting engine running conditions perfectly to all relevant parameters.

New six-speed gearbox

The R 1200 GS retains the proven principle of separating the gearbox from the engine - and at the same time the six-speed manual gearbox is an all-new development with features significantly improved once again over the previous version. Weight has been reduced to approximately 13 kg or 28.7 lb and for the first time BMW is using high-strength helical gears with smoother and more gentle gear mesh ensuring low noise and a high standard of refinement. All gear increments are designed for active riding behaviour, meaning that sixth gear is not an overdrive or economy gear, but rather has an appropriately "short" transmission ratio.

The gear shafts run in anti-friction ball bearings, the gears themselves in low-friction needle bearings. The ball bearings come in clean bearing mounts sealed at the surface to keep out even the finest particles. This allows even longer maintenance intervals and reduces the cost of service, with only one oil change required in the gearbox every 40,000 km or 25,000 miles.

The gears themselves are shifted by means of a shift roller, shift forks and shift sleeves (as opposed to shift gears used in the past) to ensure smooth positive engagement of the gears. Made of aluminium, the hollow shift roller runs on ball bearings. Detailed improvements to optimise friction on the shift box, the shift shaft and forks improves gearshift operation once again and guarantees accurate, safe mesh on all gears.

Rear Paralever

The main components of this new system are the axle drive and the swinging arm itself. Made of an ultra-strong cast aluminium alloy, the Paralever swinging arm, through its design and specific dimensions tailored to load conditions, is even lighter than before but also stiffer and stronger.

The geometric configuration of the entire swinging arm has likewise been modified, dive compensation is now almost 100 per cent. With forces acting on the final drive housing now being supported above the swinging arm, ground clearance at this point is greater than before, efficiently protecting the swinging arm even on very rough terrain against damage caused by rocks or similar objects.

The swinging arm itself is a two-piece forged aluminium unit. Another new feature is the re-configuration of the swinging arm mount moved from the final drive to the rear frame again in the interest of extra strength and robustness under the most extreme offroad conditions.

The pivot point of the axle drive unit resting in the swinging arm has been moved down to provide a more favourable geometric arrangement with greater stiffness. The bearing point, in turn, has been reinforced to match the higher load and forces from the more powerful engine.

With its improved kinematics, the driveshaft no longer changes in length as a result of geometric conditions. This also helps to save weight, since the length adjustment unit formerly fitted is no longer required. The shaft itself now comes as one single piece and - like before - runs without oil in the shaft sleeve.

The crown wheel has been re-calculated and is also lighter than before, the wheel flange now being made of aluminium in order to save weight. With its larger diameter, the flange offers the wheel better support, with additional weight-saving potentials for the rear wheel around the hub.

The hollow axle sleeve helps to dissipate heat from the final drive through its large surface and efficient flow effects. Signals for the ABS brake system and the speedometer are read by a sensor directly in front of segment pieces on the crown wheel, making the outer emitter wheel used on the former model superfluous on the new machine.

Front Telever

Refinement and modification of the front wheel geometry now further im-proves the qualities of the Telelever on the R 1200 GS over the former model. The longitudinal arm is an all-new, extra-strong and light forged aluminium component. In the interest of superior handling, front wheel camber has been reduced by 5 mm or 0.20´´ to 110 mm (4.33´´), the steering head angle remaining at 62.9° in standard position.

A change in front wheel kinematics eliminates brake dive to an insignificant residual effect actually desired to give the rider the right feeling. The superior stiffness of the Telelever, in turn, has been further enhanced by once again increasing the diameter of the support tube from 35 mm (1.38´´) to 41 mm (1.61´´), thus making a further contribution to the crisp and clear riding behaviour of the R 1200 GS.

An important detail is the holes drilled into the lower fork bridge efficiently distributing brake pressure to the steel flex brake hoses for the right and left brake callipers without requiring an additional distributor unit.

Wheel choice

The lucky purchaser of the new R 1200 GS has the choice of either high-strength cast light-alloy wheels or BMW's well-known cross-spoke wheels measuring 2.50 x 19´´ at the front and 4.00 x 17´´ at the rear and running on 110/80-19´´ and, repectively150/70-17´´ tyres.

Developed brand-new especially for the R 1200 GS, the cast light-alloy wheels with five double spokes are both stable and light. And while, at 0.1 kg, the reduction in weight at the front versus the spoke wheel is virtually negligible, weight reduction at the rear is a significant 1.6 kg, down by 12 per cent.

A big advantage of cast wheels is that they retain their excellent running smoothness and circular geometry throughout a long running life and are easier to clean. Clearly, this makes them first choice for riding on roads and untarred tracks.

'Single wire' system

Yet another special feature of the R 1200 GS is the all-new on-board electric system. The term Single-Wire System describes a highly innovative on-board network using electronics and CAN-bus technology (Controller Area Network) to offer functions and features never seen before: Reducing the number and length of cables required, this network offers a much wider range of functions than a conventional on-board network, information being transmitted along just one single path (hence "single-wire") as opposed to the double-wire system otherwise required.

Apart from the wide range of functions, the main advantages of this intelligent combination of electric and electronics are the lighter wiring harness, substantial resistance to interference, and the complete range of diagnostic functions. A further point is that the system may be flexibly expanded by simple updates.

The basic principle of the single-wire system is to connect all control units, sensors, and power-consuming items via one single, common wire in order to form a complete network transmitting all signals regardless of their subse-quent function. In other words, all information is readily available at all times within this network for all the components attached.

There is no need for conventional fuses at any point throughout the on-board network, the electronic "brain" simply switching off the function involved in the event of a short-circuit or malfunction, subsequent diagnosis serving to quickly trace and remedy the defect. And since the other functions are not affected in such a case, the network philosophy featured on the R 1200 GS again offers further advantages in terms of reliability and failsafe operation. The control units also provide relay functions, only the starter being controlled via a conventional relay.

The electrical system on the R 1200 GS is supplied with power by a low-weight alternator developing 600 W at 40 Amps. The maintenance-free battery has a capacity of 14 Ah.

Conclusion

That's it for the moment. We've found the R1100GS and R1150GS to consistently be the class leaders in this game and the bare specs of the new toy suggests that's likely to continue. Though the brand has a much tougher fight on its hands with newcomers such as KTM's 950 Adventure.

The GS is being built in three colours (yellow, red and blue) and offered with a range of accessories, including luggage. Price has yet to be confirmed. Form an orderly queue at your Bimm dealer...