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Test BMW R 1200 GS Adventure with ASC

Ah! Traction

BMW played a pioneering role in the introduction of ABS. Now the Munich-based company is following suit with another electronic driving aid and is presenting the first slip control for series motorcycles. What can the ASC?

Tyes, that went stupid. The pilot was just enjoying the serpentines of the Alpine pass and the magnificent view. But a carelessness, lost in thought at the end of the hairpin, overlooked the shovel of sand that was scattered on the road, and a gas jolt while accelerating pulled the rear wheel to the side and man and machine to the ground.

Automatic Stability Control (ASC) from BMW is intended to defuse such situations in the future. The disengageable traction control system for the K 1200 GT and all boxers costs 285 euros extra? with the exception of the R 1200 S. In the case of the GS even with an additional off-road program that allows more slip on the rear wheel.

The way it works is relatively simple. The ASC accesses the wheel speed-
ABS sensors are therefore only available in conjunction with the integral ABS. If the front and rear wheel speed differ too much, the power will be reduced. First, by fading out the ignition impulses and adjusting the ignition in the "late" direction. If that is not enough, the injection will also shut off.

Anyone who sees themselves sliding across the home route as a youngster drifter must know, however, that the ASC is not intended as a net and double floor for temporary drifters. Rather, it is intended to support the driver, to prevent the rear wheel from breaking out of the side when accelerating on slippery roads or when the grip changes rapidly. And according to BMW, that means straight ahead. But it "can, within the physical limits, reduce the rear wheel breaking sideways even when cornering"

Aha. Reduce, not prevent. And accompanied by the relativizing can. So what does the ASC really bring? Only one thing helps: try it out. The ideal location: the test site of the tire manufacturer Klèber in southern France. Irrigation system, slip surface and changing road surfaces included. Conditions that every driver dreads.

Tea speeds of the wheels are recorded by means of data recording. The irrigation system has done its job, and we can start. Damp street, second gear straight ahead, full throttle.

The boxer roars, the Adventure flies forward, the rear wheel loses its grip, and in the next moment you think the BMW is stuttering violently into the limiter or groaning with a fully pulled choke just before drowning. The ASC ?? active from a speed of ten km / h? regulates, but quite roughly. The BMW continues to accelerate. So third gear, full throttle, the same procedure. The BMW continues to accelerate, stuttering undaunted. The rear wheel stays on course except for a slight wobble.

Hairpin bend, then full shower again, this time on a more grippy surface. Before the rear wheel spins, the front wheel lifts off. But not far. Because before it really gains altitude, the ASC strikes again. It detects the drop in speed on the front wheel and thus too large a deviation from the rear wheel, which it interprets as slip. And that means ignition intervention, which is why the front wheel falls back onto the ground. The wheelie preventer is built in, so to speak.

The data recording shows that the ASC regulates around every 0.3 seconds, consequently with a frequency of almost three Hertz. However, only when the front and rear wheels rotate with a difference of more than about ten km / h. The regulation is not exactly sensitive, but it is always fast enough to keep the motorcycle stable on course when driving straight ahead.

And if you are tilted? Of course, the system has its limits. Can protect against at fall, but doesn’t have to. According to BMW, it should not allow maximum acceleration in an inclined position. Probably one of the reasons why it is not offered for the R 1200 S sports boxer. During the practical test on a damp track, the ASC actually caught the rear wheel, which was spinning at a moderate lean angle at the exit of the curve, after a moment of shock and was able to prevent a proper transverse stay in time.

The line to the uncontrolled breakaway of the rear wheel is fine, however. Does the adhesion tear off too quickly and swings the rear accordingly quickly? Due to the slippery road surface, too great a lean or too much turn on the gas ??, the ASC with its Latin at the end, the touchdown is inevitable. The testers were also able to convince themselves of this.

So why does it all work for the MotoGP racing professionals? First of all, there are defined, fairly constant grip conditions on a racetrack without too great a jump in the coefficient of friction. Furthermore, a high-revving four-cylinder can be controlled more precisely via the ignition than a low-revving twin. Above all, however, after years of development, highly complex control systems are now being used that use a variety of parameters for slip control: spring travel, throttle position, load, gear, speed via GPS. For this purpose, the different rolling circumferences of the tires are included in the inclined position, and the throttle valves are accessed by means of a servomotor. The BMW system, on the other hand, has to get by with significantly less data input, has fewer control options and regulates ?? yet ?? too rough and quite late.

At this stage, one shouldn’t expect too much from ASC. In which
the first anti-lock braking systems in 1988 also went to work in a shirt-sleeved manner, but have now reached a high degree of maturity and acceptance. A full-fledged slip control
ASC is not yet, but a start has been made.

This is how the ASC works

Acceleration while driving: The blue curves show how the speed difference between the two wheels increases to around ten km / h when accelerating in a straight line, before the ASC intervenes at intervals of around 0.3 seconds (1). As a result, the BMW accelerates more stable and better. When the ASC is switched off, the rear wheel spins so that the motor turns into the limiter in both second and third gear (2) (dark red curve).

When accelerating from a standstill, the slip peak occurs shortly after moving off (3) because the ASC only becomes active when the vehicle speed is more than ten km / h. So come
you can get away from it all on extremely slippery ground with the rear wheel spinning. However, it cannot regulate slip on the rear wheel in push mode (4).

In the off-road setting, the ASC allows significantly more slip (5), only when there is a speed difference of around 40 km / h between the two wheels does it regulate at intervals of around one second. If the difference drops to 20 km / h, the control switches off again so that you can always drive with high slip. The benefit is still very limited because you can hardly get into the control range even on loose surfaces and prefer to control such situations with the throttle.

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