Honda C-ABS

By Kevin Ash

Pictures: Honda Press, Ian Kerr
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Honda has introduced a new electronically-controlled braking system as a £1000 option on the 2009 CBR600RR and CBR1000RR Fireblade – I tried out the final-stage prototype version at the LUK Driving Centre near Baden-Baden in Germany and was very impressed. While the system, called Combined-ABS, is being touted in many places as the first ABS system for a sports bike, this is wrong on two counts: one, the year-old BMW HP2 Sport already has ABS and that’s a sports bike (if not a supersports or superbike), and two, ABS is only one function of the Honda system.

Slam on the brakes with the front-rear balance all wrong and the system converts clumsiness into refined, smooth stopping powerABS has taken a different route as it’s appearance on motorcycles to the car world. While it first appeared on high performance cars before filtering down to more mundane vehicles, it’s not appeared on superbikes because of stability problems. High performance bikes have short wheelbases and a high centre of gravity compared with most other machines so are more prone to lifting the back wheel as well as becoming unstable while the pumping action of an ABS system rapidly grips then releases the brakes.

So Combined ABS does much more. It allows normal, direct and conventional rider control of the brakes up to medium levels of braking (although the ABS will always come into play should a wheel show signs of locking up even when braking gently). Then, as the lever pressure increases further, pressure sensors detect this and the system takes over: it continues to monitor the pressures being applied at the front and rear brake levers, but cuts off the direct connection between the levers and the brake calipers. The real news here then is that this is the first brake-by-wire system fitted to a production motorcycle.
Main components add 22lb (10kg) to the bike’s weightThe ECU determines how much braking is required by the rider (judging from the brake line pressure) and distributes the braking force to the front and rear appropriately. At a little over medium braking levels the rear brake is working hard, but as the pressures increase and the rear comes close to lifting off the ground, so the braking force at the front is upped while the rear’s force is decreased.

The same system, with separate hydraulic pressure pumps and circuits for the front and rear wheels, also operates the ABS, detecting wheel lock-up and reducing the braking pressure until the wheel speed is restored.

Even when I deliberately tried to lift the rear wheel it wouldn't come upIf this sounds like a formula for interfering in feedback to the rider, and a hard-to-modulate non-linear brake action, my test ride showed nothing of the sort. Indeed, even under extreme braking it was hard to tell the system was even fitted, other than by the impressive composure of the bike regardless of the balance of front and rear brake I was applying, whether in a straight line or peeling into a corner. Weight transfer to the front is noticeably smoother than with conventional brakes, giving the bike a more stable platform as soon as braking is started. It remains more stable too as it’s almost impossible to lift the rear wheel off the ground – the system is designed to prevent this from happening, and that makes the bike much easier to control on corner entry.

Corner turn-in is slower as the bike dives less and the steering geometry is less steepYou do need to adapt your riding style though: because the bike settles more evenly as you brake for a turn, without diving violently down on its forks, the steering geometry is affected less and the bike is more reluctant on the initial turn in. Even so, with practice and the knowledge that you can’t lock up a wheel, it’s still possible to enter a corner faster, and lap times are better. You’re probably safer too, which is quite an achievement.

One of the key components, according to development engineer Oliver Fuchs, is the stroke simulator, which measures the braking pressure from the rider and passes instructions to the ECU: ‘This is very important in determining how the system feels to the rider, not just in terms of the levers but in how the bike stops in response to that,’ he says.

The ABS modulator is a very high frequency, low friction device which minimises the pulsing associated with ABS systems which can cause problems with sports bikes in particular, and it is also designed to trigger very late, closer to the wheel lock-up point than existing systems.

For the first time on a supersports bike, an ABS pulse sender ring on the front wheel...There’s no question the system works, and Honda’s claims that even top level racers find it difficult to outbrake the system are perfectly believable. This is important because conventional ABS can be beaten relatively easily by a rider concentrating on doing so, although its real value is in preventing wheel lock-up in emergency situations, when few riders would perform as well. The new system offers the same level of safety in normal road conditions but should, for most riders, enhance the bike’s performance in track or even race conditions.

There’s a substantial weight penalty as well as the cost, as the system adds 22lb (10kg) to a CBR600RR, and that is certainly noticeable, and some of the bike’s reluctance to turn in is likely due to this as much as its improved stability. On the road however the benefits are very clear and there’s no question the bike is better for Combined ABS, however much many riders will sneer at the thought of having ABS on a sports bike.

This boils down to ego more than realism, but the Honda system will still need to overcome that prejudice, so think if it not as taking away control from the rider, but taking away a lack of control. Would I opt for it on a new CBR? A qualified yes... The system itself is excellent and would add to my riding experience rather than detracting from it. But £1000 is a lot of money on top of the price of a 600. I'd rather wait until it gets cheaper.