Single-channel ABS

Single-channel ABS is the lower-cost version of two-wheeler anti-lock braking, fitted to commuter bikes and scooters where a full dual-channel system would push the price up too much. Only the front wheel carries a toothed ring and speed sensor, and the ABS unit has a single valve channel on the front brake line. The rear brake, disc or drum, is plumbed straight to the pedal with no sensor and no valve.

The reasoning is that the front brake does most of the stopping, and a locked front wheel is the one that throws a rider off. Protecting that wheel alone removes the most dangerous kind of crash. The system itself works exactly as described under Anti-lock braking system, just for one wheel.

• The front sensor reports wheel speed to the ECU.
• In a hard stop, if the front wheel slows much faster than the bike, the valve holds and releases pressure.
• The front tyre keeps rolling and the bike stays upright and steerable.
• The rear brake is untouched: stamp on it and the rear wheel can still lock and skid.
• Many single-channel bikes also fit a combined braking system that shares some pedal effort with the front.

Bikes such as the Pulsar 150 and the Honda Unicorn, and scooters such as the Aprilia SR 160 and Yamaha Aerox 155, use single-channel ABS. Above 125 cc the law requires ABS of some kind; up to 125 cc only a combined braking system is required. What you notice is a pulsing front lever in an emergency while the rear behaves like any plain brake, so the rider still has to be careful with the rear pedal. If you often ride on wet or loose roads, dual-channel is worth paying for.