Could the next big development in antilock brakes come off-road? Husqvarna thinks so, BMW’s Italian-by-way-of-Sweden dirt bike brand has adapted the S1000RR’s dual-channel ABS for off-road applications. Undergoing validation testing on Husky’s flagship TE449, the system is claimed to make threshold braking the front wheel easier and safer, while leaving the rear free to lock up, thereby facilitating slides and stops on loose surfaces.
ABS has traditionally been shunned on off-road motorcycles because existing street systems lack the ability to deal with loose surfaces and low traction. In such conditions, a rider must modulate the front wheel on the verge of locking up to achieve maximum braking, but ABS brakes developed for high-grip street use simply detect slide and don’t apply enough braking force, increasing stopping distances.
To overcome that, Husqvarna looked at the sophisticated, switchable ABS fitted to the BMW S1000RR. On that bike, selecting “Slick” mode disables rear wheel ABS to allow for brake slides, while continuing to compare front and rear wheel speeds to inform operation of the front brakes.
Antilock brakes work as the name suggests, wheel speed sensors are capable of determining when a wheel is locked or on the verge of locking and momentarily release brake pressure to prevent that happening. A visual demonstration of this effect can be seen in the dotted skid marks that now cover roadways. The tire marks are where the brakes lock, the clear spaces are where they’re released.
Maximum braking power is achieved just on the threshold of locking a wheel, but modulating lever force to maintain that exact threshold as speeds, surface and irregularities vary is a skill beyond most mortals. ABS has brought massive benefits to safety in both cars and bikes on the street, allowing operators to simply apply the desired amount of lever pressure while letting the computers sort out the safest, fastest way to slow down.
Husqvarna’s off-road system still uses sensor rings on both the front and rear wheels, but doesn’t apply ABS to the rear wheel. Instead, rear wheel data is used to inform the determination of when the front wheel is locked or on the verge of locking.
Interestingly, Husqvarna has found it necessary to build back in some of the lever pulsation of early road ABS systems, saying this is necessary to, “provide clear, transparent feedback on the braking manoeuvre.”
Husqvarna shies away from claiming improved outright braking performance, instead implying that dirt-biased ABS will make off-road riding safer and maximum braking forces more accessible to real world riders. The top picture is a good example, applying that much front brake descending such a steep hill is challenging, yet critical if you need to slow or stop on such terrain; the rear wheel is virtually unweighted. The system adds only 1.5kg to the TE449.
As ABS becomes mandatory on all street bikes in the EU in 2017 (dual sports can retain “off” switches) and as its advancing technology makes it more acceptable to the majority of riders, expect to see more bikes in more categories adopt the technology. Tellingly, Husqvarna suggests that the next development may be a mode switch, enabling dual-channel ABS to be optimized for either off- or on-road use at the push of a button.