Low overall centre of gravity, very favourable concentration of masses and ideal static wheel load distribution.
The chassis of the BMW 6-cylinder motorcycles is based on the innovative BMW Motorrad concept as already used in the current 4-cylinder models of the K series. The essential elements are the light alloy bridge-type frame, Duolever and lightweight construction Paralever for wheel control at the front and rear.
Because of the special requirements of a touring bike with a 6-cylinder engine, particular attention was paid to balancing the masses. All in all, the interplay of chassis and engine position together with the seating position of the rider not only makes for a low overall centre of gravity with a very favourable concentration of masses, it also provides a ideally balanced static wheel load distribution of 52 per cent at the front to 48 per cent at the rear (K 1600 GT unloaded). Even with a pillion passenger and a heavy load, this guarantees outstanding riding properties.
Main frame made of light alloy in a bridge-type construction combined with a light alloy rear frame.
The central bearing component is the main frame in a bridge-type construction. The entirely newly-developed aluminium lightweight construction frame consists of a welded unit with four highly rigid, heat-treated chill-cast parts with thin walls. Both the complex geometry and the large number of attachment points make very high demands in terms of manufacturing technology.
Due to the fact that the engine is tilted heavily forward, the profiles of the main frame can run above the cylinder head so their configuration is largely independent of the latter's width. This means that the frame can be very narrow, especially in the ergonomically important knee area. The main frame weighs just 16 kilograms. The 6-cylinder engine is firmly bolted to the frame at eight points and thus acts as a rigidifying element.
In spite of the demands made by a motorcycle such as the K 1600 GT/GTL in terms of pillion passenger riding and load, the developers have nonetheless succeeded in creating a rear frame in light aluminium construction. It consists of highly rigid, welded aluminium extruded sections and is bolted to the main frame at four points. The robust construction is supplemented with deformation elements in the area of the pannier support. The rear frame weighs just 4 kilograms.
BMW Duolever front wheel control for excellent ride precision, cornering predictability and comfort.
In the BMW Motorrad K series, the Duolever stands for maximum ride precision and cornering predictability. It combines the greatest possible ride comfort with a sensitive response. The spring travel is 115 millimetres (60 mm compression, 55 mm rebound).
The kinematics of the Duoloever provides automatic anti-dive control in the K 1600 models, so the longitudinal forces acting on the front wheel during braking cause virtually no compression. Only the dynamic wheel load distribution generates a slight dip which gives the rider feedback on braking power as is familiar from conventional telescopic forks. In this way the Duolever combines the desired amount of front wheel feedback with the comfort and safety benefits of anti-dive control.
Adapted BMW Paralever rear wheel swinging arm and Cardan shaft drive.
In large-volume BMW touring bikes in particular, the Cardan shaft drive is an indispensable part of the overall concept due to its numerous advantages. Based on the familiar Paralever swing arm, the rear wheel control and the Cardan shaft drive have been adapted to the new 6-cylinder engine in terms of construction requirements. In accordance with the increased performance and torque demands, the propeller shaft and rear axle final drive have been newly designed.
As always, the Paralever swinging arm is made of a highly rigid aluminium cast alloy. It is mounted directly on the rigid main frame which at this point is formed by a highly stable structure made of cast light alloy.
The torque support for the housing of the rear-wheel drive is still located above the swinging arm, while the brake caliper is now mounted at the rear in the extension of the vehicle's longitudinal axis.
The central suspension strut, adjustable via a needle valve in the damping, is controlled by means of a lever construction and is supported by a stabiliser arm on the main frame. The progression combines sensitive response of the suspension with excellent traction response while still providing sufficient reserves for riding with a full load.
The spring travel is 135 millimetres (100 mm compression, 35 mm rebound). In the standard version, the rear spring strut offers continuously variable adjustment for rebound damping and continuously variable adjustment of the spring rest by 10 millimetres by means of an adjuster knob so as to be able to adapt the rear to different load states.
The new K 1600 GT and K 1600 GTL roll on lightweight, elegantly designed light alloy cast wheels in ten-spoke design which combine an attractive shape with high rigidity and low weight. The front wheel measures 3.5 x 17 inches, the rear wheel 6.0 x 17 inches. The corresponding tyre sizes are 120/70 ZR17 at the front and 190/55 ZR17 at the rear. The rear tyre has been especially developed to meet the demands of a touring motorcycle in terms of load and speeds.
Electronic Suspension Adjustment ESA II for optimum adaptation to all uses and load states.
The new BMW K 1600 GT and K 1600 GTL also benefit from the innovative Electronic Suspension Adjustment II (ESA II) which is offered as a special equipment feature ex works.
With this system, which is globally unique on the motorcycle market, the rider can conveniently press a button to electronically adapt not only the rebound damping properties of the front and rear spring strut but also the spring rest ("spring preload") of the rear spring strut as well as the latter's spring rate and therefore the "hardness" of the suspension. This is carried out conveniently using the Multi-Controller in conjunction with the menu in the TFT colour display panel. 3
This second-generation "Electronic Suspension Adjustment" - or ESA II for short - enables the suspension settings to be adapted highly conveniently and more precisely than ever before to riding style and load, thereby achieving a whole new dimension of ride stability and comfort while offering excellent responsiveness.
In order to make operation as simple as possible and prevent unwanted, erroneous settings the rider first simply enters the load state ("solo", "solo with luggage" or "with passenger and luggage"). The relevant spring rest and spring rate are then set automatically as the system harmonises these two values.
The rider also chooses the chassis character of the machine with either "Comfort", "Normal" or "Sport", depending on the planned riding style. From these entries, the electronic control system calculates the appropriate damping rates based on optimum parameters and sets them accordingly. This means that the new 6-cylinder touring bikes offer a total of nine different setting variations.
The additional adaptation of the spring rate allows optimum adaptation of ride height to varying load states, thereby guaranteeing an even higher level of ride stability, agility and comfort. Even under maximum load with pillion passenger and luggage, this means that full banking freedom is maintained, enabling a sporty riding style. What is more, the adaptation of the spring rate drastically reduces the risk of bumping with an extreme load. Damper settings can be changed simply at the press of a switch ("Normal", "Sport", "Comfort") even while riding. For functional and safety-related reasons, the spring rest can only be changed when stationary. An electric motor with a gear unit is used to vary the spring rate. The damping rate is altered by means of small stepper motors at the dampers.
The alteration of the spring rate is effected by two springs connected in series. Here the compression forces are absorbed by an elastomer element (Cellasto) combined with a conventional coil spring underneath. The radial expansion of the Cellasto element is permanently limited by a steel sleeve. An aluminium sleeve is moved on the inside by means of an electrohydraulic mechanism. The position of this inner sleeve influences the inward expansion response of the Cellasto element and therefore its spring rate. The effect is 4
equivalent to that of two springs of differing strength. When the inner sleeve rests on the steel spring, the Cellasto element is out of function and only the steel spring takes effect. If the inner sleeve is then moved further, the spring rest of the steel spring can be varied, i.e. the "spring preload".
In this way, static normal position and ride geometry are optimally preserved in all load states. Thanks to this "ride-height levelling", the BMW K 1600 GT and BMW K 1600 GTL are just as stable when fully loaded as when only carrying a rider.
The additional adaptation of the spring rate across the range of 110 to 160 N/mm allows the settings "Sport", "Normal" and "Comfort" to be spread widely in ESA II, giving them clearly perceptible characteristics during riding. So in "Sport" mode the K 1600 GT and GTL are even more dynamic and precise and in "Comfort" mode they are more comfortable - while still retaining excellent stability.
All in all the benefits of ESA II can be summarised as follows:
- Excellent adjustment range in the settings "Sport"/"Normal"/"Comfort".
- Static normal position and ride geometry are optimally preserved in all settings.
- Optimum adaptation of damping and spring rate/spring rest in all settings.
- Significant change of vehicle character through damping adjustment.
- Excellent adaptation to all load states through spring rate/spring rest adjustment.
- Clear increase in safety in terms of braking and ride stability, cornering freedom and bump response.
Brake system with BMW Motorrad Integral ABS (part integral) for optimum deceleration.
The very highest safety standards are met by the brake system with BMW Motorrad Integral ABS in the part integral version, which is fitted as standard.
For even better controllability an additional pressure sensor was integrated in the ABS hydraulic system. In this way, maximum yet controllable deceleration at low levels of control force give the rider additional safety.
Generously sized brake disc diameters of 320 millimetres at the front and rear ensure maximum deceleration capacity even at very high speeds and under heavy loads. In many tests the system has demonstrated its further advantages such as unsurpassed speed of brake pressure build-up and very low control force even on full braking. The current system is among the safest and most effective brake systems on the market.
Traction control DTC (Dynamic Traction Control) for maximum safety when accelerating.
For both K 1600 models, traction control DTC (Dynamic Traction Control) is available as a special equipment feature ex works. It contributes significantly to a high level of riding dynamics and exemplary riding safety.
Traction control DTC was used in the supersports bike BMW S 1000 RR for the first time: it provides the rider with valuable support especially in changing conditions, on surfaces with limited grip and where there are big changes in friction levels.
By comparing the rotational speeds of the front and rear wheel via the ABS sensors and the data collected by the sensor box (banking detection), the BMS-X system detects spin in the rear wheel. In this event the system cuts back drive torque accordingly by reducing the ignition angle, adapting injection and influencing the position of the throttle valve.
Unlike previous BMW Motorrad ASC systems, the traction control system DTC also detects the banking position of the vehicle by means of sophisticated sensor clusters, taking this into account in its control response.
Traction control DTC is combined individually with the different modes and fully harmonised with it so as to provide maximum riding safety (see section 2 "Powertrain"). 6
Although DTC provides valuable support for the rider and therefore an enormous safety bonus when accelerating, just like ABS it cannot redefine the boundaries of physics. It is still possible to exceed these limits by misjudgement or riding error, which in extreme cases can lead to a fall. However, DTC (Dynamic Traction Control) does help the rider make much more effective use of the dynamic potential of the K 1600 touring bike - in particular ensuring greater safety. Nonetheless, DTC (Dynamic Traction Control) can be separately deactivated for special purposes.