Understand ABS and use it wisely
Electronic safety net for panic situations
Bob Gray Former road tester who’s spent the last 16 years working as technical advisor, engine-management technician and crew-chief for BSB teams
There are two problems with braking while cornering on a motorcycle. The first is the front loses grip and you crash. The second is the bike sits up and runs wide, and you crash. It’s not something most people try more than twice. But cornering ABS aims to change that – which is good news in panic situations, and for those who didn’t get it after the first two occasions.
Cornering ABS works by calculating the bike’s attitude (roll and pitch) using an inertial measurement unit (IMU). When the ECU thinks the bike is leaning, it limits how pressure is allowed to build in the braking system – reducing the sitting-up tendency. It also modulates the pressure based on a perception of grip (like normal ABS) – preventing the washing-out problem.
Bikes sit up if the brakes are applied suddenly while cornering because a sudden torque is generated in the steering as a result of the trail and the displacement of the tyre contact patch with the bike’s vertical plane of symmetry. In other words, dab the brakes while leaning and the bars will attempt to turn more into the corner. This has the effect of turning the bike out of the corner just like counter-steering to flick a bike through a chicane.
The lack of grip when cornering is simply down to force. Assuming a constant road surface, the more ‘downward-force’ (weight) there is on any tyre, the more it grips. When leaning, only part of a bike’s weight presses ‘vertically’ down through the tyre; the rest attempts to resist the lateral force pushing the front around the corner. Quite simply, there is less grip because the tyre isn’t being pushed into the road as hard.
From an ABS point of view, the system monitors this in the same way as when the bike is upright, but using more sensitive parameters, and safe in the knowledge that the peak pressure will never be as great as when the bike is upright.
‘Cornering ABS is good news in panic situations’
Braking in a corner doesn’t have to end badly