Braking hard in a corner: BMW's lean angle-sensitive ABS Pro
By Loz Blain
July 20, 2014
When motorcycle ABS first came out, many riders (including myself) took a dim view of it – until we tried it and realized just how incredible it was to be able to jam on the brakes fearlessly in the wet and on imperfect surfaces. But you still had to be careful putting the brakes on in a corner. Now, BMW has announced ABS Pro, the first lean angle-sensitive ABS system for a supersports bike, so road riders can brake safely, effectively and extremely quickly while you're leaning the bike over.
The standard "Race ABS" system on BMW's S1000RR was already a complex and clever system, as well as being a really effective one (heck, it saved my skin). But it seems BMW and its key supplier Bosch have figured out how to get even more value out of the massive range of wheel speed, lean angle and pitch sensors on the bike.
The BMW HP4 will soon become the first sportsbike to feature ABS Pro, an ABS system that takes lean angle into account. This means you can slam on the brakes in the corners and not pay the usual heavy price.
Braking in a corner has always been a hairy prospect for motorcyclists. Of course, it's also quite a common place to need to brake. With just two coin-sized patches of rubber providing your cornering grip on the road, jamming on the brakes can easily cause you to lose traction. On the rear wheel, this is dangerous but salvageable if you're lucky. Lose the front wheel under brakes and leaned over, and you're cactus. The "lowside" may not be the most violent type of crash, but it leaves you on the road, sliding towards the outside of the corner, where there's frequently oncoming traffic, cliffs and railings.
The ABS Pro system (most likely a tuned version of Bosch's Motorcycle Stability Control package, pictured below on the KTM 1200 Adventure) is designed to give ham-fisted riders the ability to mash the brakes on at any lean angle without over-braking.
The system pulls in data from the front and rear wheel speed sensors, brake pressure sensors, and the roll, yaw and transverse acceleration sensors from the bike's traction control system to get a very accurate picture of how fast the bike is turning, and how far it's leaned over.
The system then adjusts the maximum allowable brake pressure gradient, as well as how smoothly the ABS system intervenes in the braking process, to enable the best possible stopping power under the circumstances.
As well as helping prevent front-wheel slides and lowsides, the system also helps to proportion braking between the front and rear wheels in order to stop the bike from pushing itself upright on the brakes – so you don't run wide and brake yourself off a cliff.
The ABS Pro system is deactivated in Race and Slick modes on the HP4 as it's not designed for track use, but rather as a road riding safety tool. ABS Pro will launch at the end of October as a retrofittable option for the HP4, at a very reasonable price of EU€380 (US$514) (German pricing). We'd also expect to see it popping up on other road bikes in the next few years.
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