ABS, fully integral function / part integral function

Correct braking technique is of crucial importance to motorcyclists, and it is only the combination of a reliable braking system technology with the acquired skills of the rider, which allows critical situations to be dealt with effectively. When suddenly in danger, even experienced motorcyclists tend to excessively brake the front wheel or lock the rear wheel, so a modern antilocking system (ABS) is a required active safety feature in any high quality motorcycle. All BMW Motorrad models are thus either fitted with ABS as standard or BMW Motorrad ABS is optionally available as a factory fit. This safety feature makes braking in the wet or in other dangerous situations, such as with a pillion and luggage, as simple and as safe as possible, whether you are a beginner or an experienced rider. The optimum braking distance is thus available at all times to the rider without the danger of the wheels being locked.

BMW Motorrad uses various ABS braking systems depending on the type of motorcycle. For mid range bikes, the F 650 GS, F 650 GS Dakar and F 650 CS Scarver are the only single cylinder bikes to provide ABS optionally. In the K Series and the flat twin "boxer" models (R series), two different types of the BMW Motorrad Integral ABS are used: for all sports touring bikes, roadster models, endures, the K 1200 S sports bike and the tourer K 1200 GT the partially integral ABS is used, while all Cruisers and the K 1200 LT are fitted with the fully integral function. In the R 1200 GS and R 1150 GS Adventure, the F 650 GS and F 650 GS Dakar, the ABS function can be switched off when riding on loose surfaces.

All three systems reliably prevent the wheels from locking in the event of an emergency stop by means of an electronically controlled regulatory hydraulic system. Wheel sensors measure the rotational speed of the front and rear wheels and identify when the wheel begins to lock. The sensors pass on a measured impulse to a processor, which activates a pressure modulator in the hydraulic brake circuit of the front or rear wheel. The activated pressure modulator reduces brake pressure in a fraction of a second and then increases it once more. This means that the ABS applies just the right amount of brake pressure within the ABS range to the appropriate wheel as required to keep the wheel just short of locking point.

For the first time and only in motorcycle construction, the state of the art BMW Motorrad Integral ABS also makes use of a brake booster. An electrically operated hydraulic pump supports the brake pressure generated via the brake lever and cylinder. With the part integral brake system, the rider simultaneously activates the brakes of both wheels, with the footbrake lever only taking effect on the rear wheel brake. The fully integral brake system always decelerates both wheels, no matter whether only the hand or foot brake levers are being operated. Both systems provide a clear safety benefit when compared to conventional braking systems, that has been frequently demonstrated in motorcycle tests. In the flat twin Enduros, the partially integral function remains in place even when the ABS is deactivated.

The central pressure modulator of the integral brake houses the electronic control system and the hydraulic system of the brake booster and the antilocking system. A total of three processors ensure maximum system reliability. Two microprocessors control the regulatory system in parallel, while a third performs a monitoring function. Whenever the ignition is switched on, the system runs a self-test while the ABS control lights flash in the cockpit. They switch off automatically if the system is operating error-free and a speed of at least 4 km/h has been reached.

How does ABS Work?
The maximum braking force it is possible to transfer to the road depends, among other things, on the coefficient of friction of the road surface. A road covered with sand, gravel, ice, snow, wet leaves or water has a very low coefficient of friction when compared to a dry, clean asphalt road surface. Simply put, all other things being equal, the lower the road's coefficient of friction, the longer the braking distance.

If, when the rider is stopping the motorcycle, the maximum braking force possible to transfer to the road is exceeded, the wheels will begin to lock.Ý With wheels locked, directional stability is lost and a crash is possible.Ý

Before the wheels lock, ABS intervenes and adapts the braking pressure close to the maximum braking force it is possible to transfer so that the wheels continue to turn. Wheels that are turning, as opposed to wheels that are locked, help maintain riding stability, regardless of road conditions.

What happens on uneven road surfaces?
As a motorcycle passes over, or brakes while on, uneven or "corrugated" road surfaces, the tires, in reaction to the bumps, may temporarily lose contact with the road surface. In such cases, the braking force it is possible for the tires to apply to the road surface can drop to near zero.  If the brakes are applied in this situation, the ABS must reduce the braking pressure to help ensure riding stability when contact with the road surface is restored.  At this moment, BMW Motorrad Integral ABS must assume an extremely low coefficient of friction (as with gravel, ice, snow, etc.) so that the wheels remain in rotation and the stability of the motorcycle is maintained. Once the actual circumstances are detected, the system will set the brake pressure to an optimized value.

What do we observe during rider safety training or ABS demonstrations?
Braking in which the anti lock function is activated (ABS controlled braking) has, by comparison with normal braking, a significantly higher demand for electrical power. This puts a heavy load on the battery.Ý In normal riding, the battery has sufficient capacity available as it is constantly being charged and ABS may only be activated from time to time.

If the motorcycle is not to be ridden for several weeks, a trickle charger, which can be obtained from your BMW Motorrad dealer, should be connected or the battery should be disconnected and then recharged before the motorcycle is put back on the road again.

In organized ABS demonstrations or during some rider training courses, an unusual number of ABS controlled braking operations may take place in rapid succession. These demonstrations are combined with periods of time where the motorcycle is not ridden, when braking techniques, the feel of the motorcycle operating under ABS, the ABS experience etc. are discussed.Ý The battery is put under heavy load by the ABS control actions, but at the same time, it is not being recharged because the actual time the motorcycle is in operation is limited. In isolated cases, in this artificially created situation, braking operations in which the brake lever is operated with maximum force and extreme speed, in combination with a declining on-board voltage supply, can produce a situation in which the antilock function is not available to the rider.

Field observations carried out by BMW Motorrad indicate that a comparable situation has not occurred in real world traffic situations or during training rides.Ý

• The following points must be observed during rider training courses or in demonstrations where the anti lock function is repeatedly activated.
• Check and observe the warning and indicator lamps before each braking exercise
• Allow the BMW Motorrad Integral ABS self check to be competed before beginning any braking exercise.
• After a maximum of five (5) braking exercises, ride the motorcycle over sufficient distances and at sufficient engine RPM to recharge the battery.
• Switch off electrical "consumers" such as heated seats and heated handgrips, the radio, navigation system and all accessories connected to the power sockets.
• During breaks in the demonstration for discussion, switch off the ignition with the ignition key. Note: if the engine is switched off with the emergency ON/OFF switch, the lights and all electronic systems remain "on" and drain the battery. In addition, the normal ABS system check will be skipped when the engine is restarted.

How can I achieve the shortest braking distance?
Load distribution between the front and rear wheels changes under braking.Ý The harder the brakes are applied, the greater the load transferred to the front wheel.Ý The greater the load on the front wheel, the greater is the braking force that can be transferred.

To achieve the shortest braking distance, it is necessary to apply the front brake gradually and with increasing force.Ý This makes best use of the dynamic increase in load on the front wheel.Ý At the same time, the clutch should be disengaged.

In emergency braking, in which brake pressure is generated as quickly as possible and with all possible force, maximum braking force cannot be instantaneously transferred to the road. In these cases, ABS intervenes, reducing brake pressure as needed to ensure that the front wheel does not lock up, but extending the braking distance.

What happens if ABS control fails?
A fault in BMW Motorrad Integral ABS is indicated by a corresponding warning display in the instrument cluster.Ý If only ABS control fails, the integral system and the brake servo action remain operational.Ý If these systems also fail, the residual brake function is applied.Ý

In the residual braking function, the forces to be applied to the brake levers increase significantly and the lever travel will be longer.Ý The residual brake function is a mechanical/hydraulic function and is always available in the event of a failure of the BMW Motorrad Integral ABS, regardless of the battery condition. The residual brake function meets all requirements of legislation around the world on the design of brakes for motorcycles and allows the rider to safely brake the motorcycle. The following notes must be observed for riding with the residual brake function:

• Set the brake lever to maximum travel.
• Always brake with both front and rear brakes.
• Where it is safe to do so, try out the brakes in order to learn the brakes  response characteristics.
• Be aware of the prevailing road conditions and adapt your braking force accordingly.

Since the residual brake function is for emergencies only, you should visit an authorized BMW Motorrad dealer as quickly as possible to bring the motorcycle back to full BMW Motorrad Integral ABS capabilities.

What is the role of regular maintenance?
Any technical system is only as good as it is maintained.Ý The specified service intervals must be adhered to without fail to ensure that the BMW Motorrad Integral ABS is in optimum maintenance condition.

What is the design specification for BMW Motorrad Integral ABS?
BMW Motorrad Integral ABS is designed to ensure stability of the motorcycle on virtually any surface within the bounds of physics.

The system was not designed for special requirements such as those that are experienced under the extreme conditions of competition off-road or on the racetrack.